U.S. patent application number 16/818218 was filed with the patent office on 2020-09-17 for centrifugal pump.
This patent application is currently assigned to AISAN KOGYO KABUSHIKI KAISHA. The applicant listed for this patent is AISAN KOGYO KABUSHIKI KAISHA. Invention is credited to Yoshihiko HONDA, Hironori SUZUKI.
Application Number | 20200291954 16/818218 |
Document ID | / |
Family ID | 1000004716001 |
Filed Date | 2020-09-17 |
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United States Patent
Application |
20200291954 |
Kind Code |
A1 |
SUZUKI; Hironori ; et
al. |
September 17, 2020 |
Centrifugal Pump
Abstract
A centrifugal pump includes a housing and an impeller housed in
the housing. The impeller has a main plate, a plurality of first
blades, and a plurality of second blades. The first blades and the
second blades extend radially along the main plate and have the
same radial length. Each of the second blades has a low blade part
and a high blade part extending radially from a radially outer end
of the low blade part. When comparing the first blades and the
second blades with each other at an equal distance from a
rotational axis of the impeller, a height of the low blade part
measured from the main plate is less than a height of each first
blade measured from the main plate, and a height of the high blade
part measured from the main plate is the same as that the height of
each first blade.
Inventors: |
SUZUKI; Hironori; (Obu-shi,
JP) ; HONDA; Yoshihiko; (Obu-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AISAN KOGYO KABUSHIKI KAISHA |
Obu-shi |
|
JP |
|
|
Assignee: |
AISAN KOGYO KABUSHIKI
KAISHA
Obu-shi
JP
|
Family ID: |
1000004716001 |
Appl. No.: |
16/818218 |
Filed: |
March 13, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 29/4206 20130101;
F04D 29/22 20130101 |
International
Class: |
F04D 29/22 20060101
F04D029/22; F04D 29/42 20060101 F04D029/42 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2019 |
JP |
2019-048250 |
Claims
1. A centrifugal pump, comprising: a housing defining a discharge
passage and a suction passage therein; and an impeller configured
to rotate about a rotational axis in a rotational direction,
wherein the impeller is disposed in the housing and is coaxially
aligned with the suction passage, wherein: the impeller comprises:
a main plate having a circular shape and a top surface facing the
suction passage; a plurality of first blades extending radially
along the top surface of the main plate, and a plurality of second
blades extending radially along the top surface of the main plate,
a radial length of each of the first blades is equal to a radial
length of each of the second blades, each of the second blades has
a low blade part and a high blade part extending radially outward
from a radially outer end of the low blade part, a height of the
low blade part measured from the main plate is less than a height
of each of the first blades measured from the main plate when
comparing the first blades and the second blades with each other at
an equal distance from the rotational axis, and a height of the
high blade part measured from the main plate is the same as the
height of each of the first blades measured from the main plate
when comparing the first blades and the second blades with each
other at an equal distance from the rotational axis.
2. The centrifugal pump of claim 1, wherein the height of the low
blade part measured from the main plate continuously increases
moving radially outward along the low blade part.
3. The centrifugal pump of claim 1, wherein the height of each
second blade measured from the main plate increases at a boundary
between the low blade part and the high blade part thereof in a
stepped manner.
4. The centrifugal pump of claim 1, wherein: the main plate has a
projection part protruding in an axial direction along the
rotational axis and a flat part extending radially outward from a
radially outer periphery of the projection part, the flat part is
oriented perpendicular to the rotational axis, an axial length of
the projection part increases moving radially inward along the
projection part, and the low blade part is formed on the projection
part and does not extend along the flat part.
5. The centrifugal pump of claim 4, wherein: each of the first
blades includes a thin blade part and a thick blade part, the thick
blade part extends radially outward from a radially outer end of
the thin blade part, a thickness of the thin blade part relative to
the rotational direction is less than a thickness of each of the
second blades relative to the rotational direction when comparing
the first blades and the second blades with each other at an equal
distance from the rotational axis, and a thickness of the thick
blade part relative to the rotational direction is the same as of
the thickness of each of the second blades when comparing the first
blades and the second blades with each other at an equal distance
from the rotational axis.
6. The centrifugal pump of claim 5, wherein the thin blade part is
formed on the projection part and does not extend along the flat
part.
7. The centrifugal pump of claim 4, wherein: each of the second
blades includes a thin blade part and a thick blade part, the thick
blade part extends radially outward from a radially outer end of
the thin blade part, a thickness of the thin blade part relative to
the rotational direction is less than a thickness of each of the
first blades relative to the rotational direction when comparing
the first blades and the second blades with each other at an equal
distance from the rotational axis, and a thickness of the thick
blade part relative to the rotational direction is the same as the
thickness of each of the first blades when comparing the first
blades and the second blades with each other at an equal distance
from the rotational axis.
8. The centrifugal pump of claim 7, wherein the thin blade part is
formed on the projection part and does not extend along the flat
part.
9. The centrifugal pump of claim 1, wherein the plurality of first
blades and the plurality of second blades are arranged in a regular
manner relative to the rotational direction.
10. The centrifugal pump of claim 9, wherein the plurality of first
blades and the plurality of second blades are alternately arranged
in the rotational direction.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to Japanese patent
application serial number 2019-048250, filed Mar. 15, 2019, which
is hereby incorporated herein by reference in its entirety for all
purposes.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND
[0003] This disclosure relates generally to centrifugal pumps.
[0004] One type of conventional centrifugal pump includes a housing
defining a pump chamber therein and an impeller, which is housed in
the pump chamber and has a plurality of blades. When the
centrifugal pump is running, a fluid is suctioned into the pump
chamber via an inlet port and supplied toward a central portion of
the impeller. Most of the fluid flows from a space just above the
central portion of the impeller into spaces between the blades
through openings, each of which is defined by radially inner ends
of circumferentially adjacent pairs of the blades. Then, the fluid
is forced by the blades from the pump chamber to the outside via an
outlet port.
BRIEF SUMMARY
[0005] In one aspect of this disclosure, a centrifugal pump
includes a housing and an impeller configured to be rotated about a
rotational axis in a rotational direction. The housing defines a
discharge passage and a suction passage therein. The impeller is
housed in the housing and is coaxially aligned with the suction
passage. The impeller includes a main plate, a plurality of first
blades extending across the main plate, and a plurality of second
blades extending across the main plate. The main plate has a
circular shape and a top surface facing the suction passage. The
first blades extend radially along the top surface of the main
plate. The second blades extend radially along the top surface of
the main plate. The radial length of each first blade is equal to
the radial length of each second blade. Each second blade has a low
blade part and a high blade part extending radially outward from a
radially outer end of the low blade part. The low blade part of
each second blade has a height measured axially from the main plate
that is less than a height of each first blade measured axially
from the main plate when comparing the heights of the first blades
and the heights of the low blade parts of the second blades at an
equal radial distance from the rotational axis. The high blade part
of each second blade has a height measured axially from the main
plate that is the same as the height of each first blade when
comparing the heights of the first blades and the heights of the
high blade parts of the second blades at an equal radial distance
from the rotational axis.
[0006] In accordance with this aspect, a difference between the
amount of the fluid forced by each first blade and the amount of
the fluid forced by each second blade can be reduced, while
ensuring a relatively large area of each opening of the impeller.
Accordingly, the pump efficiency of the centrifugal pump can be
improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] For a detailed description of the preferred embodiments of
the present teaching, reference will now be made to the
accompanying drawings.
[0008] FIG. 1 is a cross-sectional view of a first embodiment of a
centrifugal pump in accordance with the principles described
herein.
[0009] FIG. 2 is a perspective view of the impeller of the
centrifugal pump of FIG. 1.
[0010] FIG. 3 is a plan view of the impeller of the centrifugal
pump of FIG. 1.
[0011] FIG. 4 is a cross-sectional view of the impeller of FIG. 3
taken along line IV-IV in FIG. 3.
[0012] FIG. 5 is a cross-sectional view of the impeller of FIG. 3
taken along line V-V in FIG. 3.
[0013] FIG. 6 is a plan view of another embodiment of an impeller
in accordance with the principles described herein.
[0014] FIG. 7 is a perspective view of a third embodiment of an
impeller in accordance with the principles described herein.
[0015] FIG. 8 is a plan view of the impeller of FIG. 7.
[0016] FIG. 9 is a cross-sectional view of the impeller of FIG. 8
taken along line IX-IX in FIG. 8.
[0017] FIG. 10 is a cross-sectional view of the impeller of FIG. 8
taken along line X-X in FIG. 8.
[0018] FIG. 11 is a perspective view of a fourth embodiment of an
impeller in accordance with the principles described herein.
[0019] FIG. 12 is a plan view of the impeller of FIG. 11.
[0020] FIG. 13 is a cross-sectional view of the impeller of FIG. 12
taken along line in FIG. 12.
[0021] FIG. 14 is a cross-sectional view of the impeller of FIG. 12
taken along line XIV-XIV in FIG. 12.
[0022] FIG. 15 is a side view of a second blade of the impeller of
FIG. 12 viewed along line XV in FIG. 12.
[0023] FIG. 16 is a side view of a first blade of the impeller of
FIG. 12 viewed along line XVI in FIG. 12.
DETAILED DESCRIPTION
[0024] In general, the shape of the blades of a centrifugal pump
affects the pumping efficiency. Consequently, various types of
blades have been provided for the purpose of improving the pump
efficiencies of centrifugal pumps. For example, in Japanese
Laid-Open Patent Publication No. H11-218097, an impeller includes a
plurality of first blades and a plurality of second blades that are
shorter than the first blades. The first blades extend radially
from a central portion of the impeller to a radially outer
periphery of the impeller. The second blades extend radially from a
region spaced from the central portion of the impeller to a
position proximal the radially outer periphery of the impeller. In
such centrifugal pumps, the second blades do not extend to or
proximal the central portion of the impeller. As a result, an
opening is defined between the radially inner ends of each pair of
circumferentially adjacent first blades. The area of each such
opening can be increased to improve the pump efficiency. However,
because the second blades are shorter than the first blades, the
volume of a fluid forced by each second blade is generally less
than the volume of the fluid forced by each first blade. Therefore,
there has been a need for an improved centrifugal pump.
[0025] A centrifugal pump generally includes an impeller and a
housing forming a pump chamber for housing the impeller therein.
The impeller has a main plate with a substantially circular shape
and a plurality of blades extending radially along a top surface of
the main plate from proximal a center of the impeller to a radially
outer periphery of the impeller. When the centrifugal pump is
operated, the impeller is rotated about a rotational axis such in a
rotational direction such that a fluid is forced forward by the
blades of the impeller relative to the rotational direction in the
pump chamber so as to flow radially outward. As a result, the
centrifugal pump suctions the fluid into the pump chamber and
discharges the fluid from the pump chamber.
[0026] One conventional method for improving the pump efficiency of
a centrifugal pump is to increase the number of blades. However,
when too many conventional blades are provided on the main plate of
the impeller, a space near the central portion of the impeller is
crowded with radially inner ends of the blades. Thus, an area of
each opening, through which the fluid flows from a space just above
the central portion of the impeller into spaces between the blades,
is relatively small. In such state, the flow of fluid from the
space just above the central portion of the impeller into the
spaces between the blades is limited, so that the pump efficiency
cannot be improved effectively. Each opening is defined by the
radially inner ends of each pair of circumferentially adjacent
blades and the top surface of the main plate near the center of the
impeller. In this disclosure, the area of the opening may also be
referred to as "opening area."
[0027] To improve the pump efficiency of the centrifugal pump,
embodiments described herein are directed to impellers having two
kinds of blades for simultaneously increasing both the opening area
and the number of the blades on the main plate. More specifically,
as shown in FIG. 6, the impeller includes a plurality of long
blades and a plurality of short blades. The long blades are longer
than the short blades in a plan view of the impeller. The long
blades and the short blades extend radially inward from the outer
circumferential periphery of the impeller and are alternately
arranged in a circumferential direction of the impeller. A radial
distance between the central, rotational axis of the impeller and a
radially inner end of each long blade is less than a radial
distance between the central, rotational axis of the impeller and a
radially inner end of each short blade in the plan view of the
impeller. In this case, the radially inner ends of the short blades
do not extend radially to a central portion of the impeller, so
that each opening at the central portion of the impeller is defined
by the radially inner ends of each pair of circumferentially
adjacent long blades. Thus, the opening area of each opening can be
increased in comparison with a conventional impeller with the same
total number of blades, but with each blade extending radially from
or proximal the central portion of the impeller to the outer
periphery of the impeller.
[0028] As described above, regarding the example of the impeller
shown in FIG. 6, the radial distance between the rotational axis
and the radially inner end of each short blade is greater than the
radial distance between the rotational axis and the radially inner
end of each long blade. Thus, in a space within a predetermined
radial distance from the rotational axis of the impeller in the
plan view, the fluid is forced by the long blades only, and is not
forced by the short blades. Accordingly, the amount of the fluid
forced by the long blades is significantly greater than that of the
short blades. Therefore, there has been a need for an improved
centrifugal pump.
[0029] The following discussion is directed to various exemplary
embodiments. However, one skilled in the art will understand that
the examples disclosed herein have broad application, and that the
discussion of any embodiment is meant only to be exemplary of that
embodiment, and not intended to suggest that the scope of the
disclosure, including the claims, is limited to that
embodiment.
[0030] A first embodiment will be described with reference to FIGS.
1 to 5. In the first embodiment, a centrifugal pump 10 is used as a
purge pump mounted on a vehicle, such as an automobile, for
supplying a deficiency of a purge flow from a canister to an intake
passage of an internal combustion engine. In each drawing, X
direction shows the rightward direction, Y direction shows the
forward direction, and Z direction shows the upward direction, such
that X direction, Y direction, and Z direction are perpendicular to
each other. However, these directions do not limit the orientation
or the mounting direction of the centrifugal pump 10 on the
vehicle.
[0031] As shown in FIG. 1, the centrifugal pump 10 includes a motor
12, an impeller 140 configured to be rotated by the motor 12, and a
housing 16 that houses both the motor 12 and the impeller 140
therein. The motor 12 may be a brushless motor. The motor 12
includes a rotor 18, a shaft 20, and a stator 22. The rotor 18 has
a hollow cylindrical shape. The shaft 20 has a lower end that is
coaxially inserted into the rotor 18. The stator 22 surrounds an
outer circumference of the rotor 18. The rotor 18 includes a
plurality of permanent magnets, such that the rotor 18 shows
magnetic poles aligned in a circumferential direction relative to a
central axis of the shaft 20. The stator 22 includes a plurality of
coils surrounding the outer circumference of the rotor 18 by a
predetermined distance.
[0032] The shaft 20 has an upper end coaxially inserted into a
central hole 142 of the impeller 140, such that the shaft 20 is
configured to transmit torque, generated between the rotor 18 and
the stator 22, to the impeller 140. The housing 16 includes a first
housing part 24 and a second housing part 26. Each of the first
housing part 24 and the second housing part 26 may be made from a
resin material. The first housing part 24 and the second housing
part 26 are coupled to each other to define a pump chamber 28. The
impeller 140 is housed in the pump chamber 28, such that the
impeller 140 can rotate in the pump chamber 28 without coming into
contact with an inward facing surface of the housing 16. The first
housing part 24 has a suction part 30 having a hollow cylindrical
shape extending upward. The suction part 30 defines a suction
passage 32 therein. The suction part 30 includes an inlet port 34
at an upstream end of the suction passage 32, i.e. at an opposite
end to the pump chamber 28. The suction passage 32 provides fluid
communication between the pump chamber 28 and the exterior of the
centrifugal pump 10 via the inlet port 34. The first housing part
24 has a discharge part 36 extending in a tangential direction from
an outer periphery of the impeller 140 (rightward in FIG. 1). The
discharge part 36 defines a discharge passage 38 therein. The
discharge part 36 includes an outlet port 40 at a downstream end of
the discharge passage 38, i.e. at an opposite end to the pump
chamber 28. The discharge passage 38 provides fluid communication
between the pump chamber 28 and the exterior of the centrifugal
pump 10 via the outlet port 40.
[0033] The centrifugal pump 10 includes bearings 42, 44. Each of
the bearings 42, 44 is composed of a ball bearing having both an
outer ring and an inner ring, such that the outer ring is fixedly
inserted into the second housing part 26 by press-fitting and that
the inner ring is fixed on the shaft 20. Due to this configuration,
the bearings 42, 44 support the shaft 20 while allowing the shaft
20 to rotate.
[0034] The second housing part 26 houses a control unit 46 at a
lower end part thereof. The control unit 46 is coupled to a
connector configured to be connected to an external power source,
such as a battery mounted on the vehicle. The control unit 46 is
configured to receive electric power from the external power source
and to supply it to the stator 22.
[0035] Next, the impeller 140 will be described in detail. As shown
in FIG. 3, the impeller 140 is configured to rotate about a
central, rotational axis C in a rotational direction R that is
clockwise in a plan view of the impeller 140. As shown in FIGS. 1
to 3, the impeller 140 includes a main plate 144 having a
substantially circular shape, a plurality of first blades 146
extending from the main plate 144, and a plurality of second blades
148 extending from the main plate 144. The main plate 144 has a top
surface facing the suction passage 32. The first blades 146 and the
second blades 148 are formed on the top surface of the main plate
144. As shown in FIGS. 2 to 5, the main plate 144 has a projection
part 152 protruding upward at a central portion thereof and a flat
part 150 extending radially outward from an outer periphery of the
projection part 152, such that the outer periphery of the
projection part 152 is contiguous with a radially inner periphery
of the flat part 150. The flat part 150 is oriented perpendicular
to the rotational axis C of the impeller 140. As shown in FIGS. 4
and 5, the projection part 152 has an inclined surface 154
continuously increasing the height thereof moving radially inward
from the flat part 150.
[0036] The first blades 146 and the second blades 148 extend
radially along the top surface of the impeller 140 on both the
projection part 152 and the flat part 150. As shown in FIG. 3, in
the plan view along the rotational axis C of the impeller 140, each
of the first blades 146 has substantially the same shape and the
same radial length as each of the second blades 148. In this
disclosure, a radial length of a blade is the length of the blade
in a radial direction and may be calculated by subtracting the
radius of the central hole 142 from the radial distance between the
rotational axis C and the radially outer end of the blade in the
plan view. The first blades 146 and the second blades 148 are
alternately arranged at regular intervals in the circumferential
direction. The first blades 146 and the second blades 148 protrude
perpendicularly upward from the top surface of the main plate
144.
[0037] As shown in FIG. 3, in the plan view of the impeller 140,
each of the blades 146, 148 is gently curved, such that the
radially inner end thereof is positioned forward of a virtual line
passing through the rotational axis C and the radially outer end of
the corresponding blade relative to the rotational direction R of
the impeller 140.
[0038] The second blades 148 have the same shape as each other, so
that one of the second blades 148 will be described for convenience
of explanation. As shown in FIG. 5, the second blade 148 has a
radially inner low blade part 156 and a radially outer high blade
part 158. The low blade part 156 is positioned proximal the central
hole 142 of the main plate 144. Regarding the height from the main
plate 144, the low blade part 156 of the second blade 148 is less
than the first blades 146 when comparing them to each other at any
given radial distance from the rotational axis C. The high blade
part 158 is positioned radially outward of the low blade part 156.
Regarding the height from the main plate 144, the high blade part
158 of the second blade 148 is equal to the first blades 146 at any
given radial distance from the rotational axis C. In this
embodiment, the low blade part 156 is formed on the projection part
152 only, whereas the high blade part 158 extends along both the
projection part 152 and the flat part 150. Thus, as shown in FIG.
5, a boundary, which is identified with a boundary line B, between
the low blade part 156 and the high blade part 158 is positioned
just above the projection part 152. The height of the low blade
part 156 continuously increases moving radially toward the boundary
line B. In this disclosure, the height of each blade from the main
plate is the distance measured from the main plate to an upper end
point of the blade in a direction along a virtual line, passing the
upper end point and being normal to the top surface of the main
plate, in a cross-sectional view of the blade along a plane
parallel to the rotational axis C.
[0039] Next, an operation of the centrifugal pump 10 will be
described with reference to FIG. 1. When the control unit 46
supplies electric power to the stator 22, the stator 22 produces a
magnetic field. The rotor 18 is rotated by the magnetic field, such
that the shaft 20, the inner rings of the bearings 42, 44, and the
impeller 140 are integrally rotated with the rotor 18 about
rotational axis C in rotational direction R. Due to rotation of the
impeller 140, a fluid, i.e. purge gas is suctioned into the suction
passage 32 via the inlet port 34 in a suction direction Y1 and
flows through the suction passage 32 toward the central portion of
the impeller 140. Then, the fluid is forced by the first blades 146
and the second blades 148 in the rotational direction R of the
impeller 140 while flowing radially outward along the top surface
of the main plate 144. As a result, the fluid is pressurized and is
discharged from the outlet port 40 via the discharge passage 38 in
a discharge direction Y2.
[0040] In accordance with the first embodiment, regarding the
height from the main plate 144, the low blade part 156 of each
second blade 148 is less than each first blade 146 when comparing
the first blades 146 and the second blades 148 to each other at an
equal distance from the rotational axis C. Thus, an opening area of
each opening of the impeller 140 can be increased in comparison
with a case where the height of each second blade 148 is the same
as that of each first blade 146 over the entire radial length
thereof. Further, in a space near the central portion of the
impeller 140, most of the fluid flows radially outward due to
inclination of the inclined surface 154, so that the amount of the
fluid moved by the low blade part 156 of each second blade 148 is
substantially the same as, and in particular, slightly less than
the amount of the fluid moved by each first blade 146. Thus, the
amount of the fluid forced by the second blades 148 can be
increased, thereby decreasing a difference between the amount of
the fluid forced by the first blades 146 and the amount of the
fluid forced by the second blades 148. Such difference may cause
pulsations in the fluid flow. Accordingly, the pump efficiency of
the centrifugal pump 10 can be improved, while preventing the
pulsations in the fluid flow.
[0041] The height of the low blade part 156 of each second blade
148 from the main plate 144 continuously increases moving radially
outward from the radially inner end to the radially outer end
thereof. Due to this configuration, the impeller 140 can be easily
produced by using molds.
[0042] The main plate 144 includes the projection part 152 and the
flat part 150 extending radially outward from the projection part
152. In a radially inner space positioned above the projection part
152, the fluid is not pressurized sufficiently by the first blades
146 and the second blades 148, and thus, the fluid flows along the
inclined surface 154. In a radially outer space positioned above
the flat part 150, the fluid is forced and sufficiently pressurized
by the first blades 146 and the second blades 148 to be moved
forward relative to the rotational direction R and radially
outward. Accordingly, each second blade 148, having the low blade
part 156 on the projection part 152 and the high blade part 158
extending over the entire radial length of the flat part 150, can
sufficiently force the fluid to flow above the flat part 150.
[0043] The first blades 146 and the second blades 148 are
alternately arranged at regular intervals in the circumferential
direction of the impeller 140. Thus, the opening area of each
opening of the impeller 140 can be held substantially constant in
the circumferential direction of the impeller 140. Further, the
difference between the amounts of the fluid forced by each of the
first blades 146 and the second blades 148 can be decreased.
[0044] A second embodiment will be described with reference to
FIGS. 7 to 10. The second embodiment is substantially the same as
the first embodiment described above, with some differences
regarding the shape of an impeller 240. Thus, while the differences
will be described, similar configurations will be described shortly
or will not be described in the interest of conciseness.
[0045] As shown in FIG. 7, the impeller 240 includes a main plate
244 having a substantially circular shape, a plurality of first
blades 246 extending along the main plate 244, and a plurality of
second blades 248 extending along the main plate 244. The main
plate 244 has a central hole 242 at a central portion thereof and a
top surface facing upward. The first blades 246 and the second
blades 248 are formed on the top surface of the impeller 240. The
main plate 244 has a projection part 252 protruding upward at a
central portion of the main plate 244, and a flat part 250
extending radially outward from a radially outer periphery of the
projection part 252. As shown in FIGS. 9 and 10, the projection
part 252 has an inclined surface 254 that continuously increasing
in axial height moving radially inward.
[0046] As shown in FIG. 7, the first blades 246 and the second
blades 248 extend radially along the projection part 252 and the
flat part 250. More specifically, each of the first blades 246 and
the second blades 248 extends radially from a radially inner
periphery of the inclined surface 254 of the projection part 252 to
a radially outer periphery of the flat part 250. The radial length
of each first blade 246 is equal to that of each second blade 248.
The first blades 246 and the second blades 248 are alternately
arranged on the main plate 244 at regular intervals in the
circumferential direction of the impeller 240. The first blades 246
and the second blades 248 are oriented perpendicular to the main
plate 244 (parallel to the rotational axis C).
[0047] As shown in FIG. 8, in a plan view along the rotational axis
C of the impeller 240, each of the first blades 246 and the second
blades 248 is positioned along a virtual line extending radially
through the rotational axis C. Thus, an inlet angle of each of the
first blades 246 and the second blades 248 is 90 degrees. An outlet
angle of each of the first blades 246 and the second blades 248 is
also 90 degrees.
[0048] The first blades 246 have the same shape as each other, so
that one of the first blades 246 will be described in the interest
of conciseness. The second blades 248 also have the same shape as
each other, so that one of the second blades 248 will be described
for convenience of explanation. As shown in FIG. 8, the first blade
246 has a radially inner thin blade part 260 and a radially outer
thick blade part 262. The thin blade part 260 extends radially
outward from a radially inner periphery of the projection part 252.
The thin blade part 260 of the first blade 246 is thinner than the
second blade 248 when comparing them to each other at an equal
distance from the rotational axis C. The thick blade part 262
extends radially outward from a radially outer end of the thin
blade part 260. The thickness of the thick blade part 262 is equal
to that of the second blade 248 when comparing them to each other
at an equal distance from the rotational axis C. The thin blade
part 260 is formed on the projection part 252 of the main plate 244
only, whereas the thick blade part 262 is formed on both the
projection part 252 and the flat part 250. Thus, a boundary between
the thin blade part 260 and the thick blade part 262 is positioned
just above the projection part 252. As shown in FIG. 8, the
thickness of the second blade 248 is constant over the whole radial
length thereof. The thickness of the second blade 248 may be 1 mm.
The thickness of the thin blade part 260 of the first blade 246 is
preferably half of the thickness of the thick blade part 262. The
thickness of the thin blade part 260 may be 0.5 mm. In this
disclosure, the thickness of each blade refers to a dimension of
the blade in the front-rear direction relative to the rotational
direction R (i.e., the circumferential direction).
[0049] As shown in FIGS. 7 and 10, the second blade 248 has a
radially inner low blade part 256 and a radially outer high blade
part 258. The low blade part 256 extends radially outward from the
radially inner periphery of the inclined surface 254. The high
blade part 258 extends radially outward from a radially outer end
of the low blade part 256. As shown in FIGS. 9 and 10, the height
of the low blade part 256 from the main plate 244 is less than that
of the first blade 246 when comparing them to each other at an
equal distance from the rotational axis C. The height of the high
blade part 258 from the main plate 244 is equal to that of the
first blade 246 when comparing them to each other at an equal
distance from the rotational axis C. As shown in FIG. 10, the low
blade part 256 is formed on the projection part 252 of the main
plate 244 only, whereas the high blade part 258 is formed on both
the projection part 252 and the flat part 250. Thus, a boundary,
which is identified by a boundary line B, between the low blade
part 256 and the high blade part 258 is positioned just above the
projection part 252. The height of the second blade 248 from the
main plate 244 increases at the boundary line B between the low
blade part 256 and the high blade part 258 in a stepped manner
moving radially outward. More specifically, the height of the
second blade 248 from the main plate 244 drastically increases at
the boundary line B. The stepped shape may have a projecting part
and a recessed part, each forming an angle 85 to 95 degrees in a
cross-sectional view of the second blade 248, taken along a plane
including both the rotational axis C and a longitudinal axis of the
second blade 248.
[0050] In accordance with the second embodiment, the first blades
246 and the second blades 248 have the same radial length as each
other. Each of the second blades 248 has the low blade part 256 and
the high blade part 258. Each low blade part 256 is formed proximal
the central portion of the impeller 240. The height of each low
blade part 256 from the main plate 244 is less than that of each
first blade 246 when comparing the first blades 246 and the second
blades 248 to each other at an equal distance from the rotational
axis C. Each high blade part 258 extends radially outward from the
radially outer end of the corresponding low blade part 256. The
height of each high blade part 258 from the main plate 244 is equal
to that of each first blade 246 when comparing them to each other
at an equal distance from the rotational axis C. Due to this
configuration, the difference between the amount of the fluid
forced by the first blades 246 and the amount of the fluid forced
by the second blades 248 can be reduced, while increasing an
opening area of each opening of the impeller 240. Accordingly, the
pump efficiency of the centrifugal pump 10 can be improved.
[0051] The height of each second blade 248 from the main plate 244
increases at the boundary line B between the low blade part 256 and
the high blade part 258 in the stepped manner. Thus, the height of
each low blade part 256 can be sufficiently lowered over the whole
radial length thereof.
[0052] Each second blade 248 includes the low blade part 256 formed
on the projection part 252 only and the high blade part 258
extending radially over the whole radial length of the flat part
250. Thus, each second blade 248 has a sufficient height to
pressurize and force the fluid to flow radially outward on the flat
part 250.
[0053] Each first blade 246 has the thin blade part 260 and the
thick blade part 262. The thin blade part 260 of each first blade
246 is thinner than each second blade 248 when comparing them to
each other at an equal distance from the rotational axis C. The
thickness of each thick blade part 262 is equal to that of each
second blade 248 when comparing them to each other at an equal
distance from the rotational axis C. Thus, the opening area of each
opening of the impeller 240 can be increased in comparison with a
case where each first blade 246 has the thickness same as the thick
blade part 262 over the whole radial length thereof.
[0054] Each first blade 246 has the thin blade part 260 and the
thick blade part 262, which extends radially outward from the
radial outer end of the thin blade part 260 and is thicker than the
thin blade part 260. Thus, the strength of each first blade 246 can
be increased in comparison with a case where each first blade 246
has the thickness same as the thin blade part 260 over the whole
radial length thereof.
[0055] The first blades 246 and the second blades 248 are
alternately arranged in the circumferential direction of the
impeller 240. Thus, the opening area of each opening of the
impeller 240 can be held to be substantially constant in the
circumferential direction of the impeller 240. Further, the
difference between the amounts of the fluid forced by each of the
first blades 246 and the second blades 248 can be decreased.
[0056] A third embodiment will be described with reference to FIGS.
11 to 16. The third embodiment is substantially the same as the
first embodiment described above, with some differences regarding
the shape of an impeller 340. Thus, while the differences will be
described, similar configurations will be described shortly or will
not be described in the interest of conciseness.
[0057] As shown in FIGS. 11 and 12, the impeller 340 is configured
to be rotated about a central, rotational axis C in the rotational
direction R that is clockwise direction in a plan view along the
rotational axis C of the impeller 340. The impeller 340 includes a
main plate 344 having a substantially circular shape, a plurality
of first blades 346 extending along the main plate 344, and a
plurality of second blades 348 extending along the main plate 344.
The main plate 344 has a central hole 342 at a central portion
thereof and a top surface facing upward. The first blades 346 and
the second blades 348 are formed on the top surface of the main
plate 344. The main plate 344 has a projection part 352 protruding
upward and a flat part 350 extending radially outward from a
radially outer periphery of the projection part 352. The projection
part 352 has an inclined surface 354 that continuously increases in
axial height moving radially inward.
[0058] Each of the first blades 346 and the second blades 348
extends radially from a radially inner periphery of the inclined
surface 354 of the projection part 352 to a radially outer
periphery of the flat part 350. As shown in FIG. 12, in the plan
view along the rotational axis C of the impeller 340, the radial
length of each first blade 346 is equal to that of each second
blade 348. The first blades 346 and the second blades 348 are
alternately arranged at regular intervals in the circumferential
direction of the impeller 340.
[0059] The first blades 346 have the same shape as each other, and
the second blades 348 also have the same shape as each other. Thus,
one of the first blades 346 and one of the second blades 348 will
be described below in the interest of conciseness. Regarding each
of the first blade 346 and the second blade 348, in the plan view
along the rotational axis C, a radially inner end thereof is
positioned, relative to the rotational direction R, in front of a
virtual line extending radially from the rotational axis C to a
radially outer end thereof. In the plan view, an upper edge of each
of the first blades 346 and the second blades 348 is gently curved
rearward relative to the rotational direction R moving radially
outward.
[0060] As shown in FIGS. 11 and 12, the first blade 346 is divided
into a first inner blade part 364 and a first outer blade part 366.
The first inner blade part 364 extends radially outward from the
radially inner periphery of the inclined surface 354. The first
outer blade part 366 extends radially outward from a radially outer
end of the first inner blade part 364 to the radially outer
periphery of the impeller 340.
[0061] As shown in FIG. 12, in the plan view along the rotational
axis of the impeller 340, the first inner blade part 364 is
positioned, relative to the rotational direction R, in front of a
radial reference line N1, extending radially and passing through
the rotational axis C and a connection part between the first inner
blade part 364 and the first outer blade part 366. The connection
part between the first inner blade part 364 and the first outer
blade part 366 corresponds to a radially inner end of the first
outer blade part 366. The first outer blade part 366 has a front
surface 366F facing forward and a rear surface 366R facing rearward
relative to the rotational direction R. In some embodiments, the
radial reference line N1 may pass the front surface 366F of the
first outer blade part 366 at the radially inner end of the first
outer blade part 366.
[0062] As shown in FIG. 11, the first inner blade part 364 has a
front surface 364F facing forward and a rear surface 364R facing
rearward relative to the rotational direction R The front surface
364F and the rear surface 364R extend perpendicular to the top
surface of the main plate 344. In some embodiment, an angle formed
between the top surface of the main plate 344 and each of the front
surface 364F and the rear surface 364R may be between 85 to 95
degrees.
[0063] The front surface 366F of the first outer blade part 366
extends from the top surface of the main plate 344 obliquely
rearward relative to the rotational direction R of the impeller
340. The front surface 366F is contiguous with the front surface
364F of the first inner blade part 364. As shown in FIGS. 13 and
14, the front surface 366F extends linearly between an upper end
and a lower end thereof in a cross-sectional view perpendicular to
a longitudinal axis of the first outer blade part 366. The front
surface 366F may be gently curved in a concave or convex manner in
some embodiments.
[0064] In a cross-sectional view perpendicular to the longitudinal
axis of the first outer blade part 366, an angle .theta. formed
between the front surface 366F of the first outer blade part 366
and a first vertical reference line L, which extends parallel to
the rotational axis C and passes through the upper end of the front
surface 366F, is acute and continuously increases moving radially
outward.
[0065] As shown in FIG. 12, in the plan view along the rotational
axis C of the impeller 340, a lower portion of the front surface
366F of a radially outer end of the first outer blade part 366 is
positioned in front of the radial reference line N1 relative to the
rotational direction R. And, an upper portion of the front surface
366F of the radially outer end of the first outer blade part 366 is
positioned rearward of the radial reference line N1 relative to the
rotational direction R. This configuration is illustrated in FIGS.
13 and 14 more clearly. In FIGS. 13 and 14, the lower portion of
the front surface 366F is positioned, relative to the rotational
direction R, in front of a second vertical reference line N1',
which extends vertically and perpendicular to the radial reference
line N1. The upper portion of the front surface 366F is positioned
rearward of the second vertical reference line N1' relative to the
rotational direction R. As shown in FIG. 11, a radially outer
surface of the first outer blade part 366 is flush with the
radially outer periphery of the main plate 344.
[0066] As shown in FIGS. 13 and 14, the thickness T of the first
outer blade part 366 in a front-rear direction relative to the
rotational direction R (i.e., circumferential direction)
continuously increases from an upper end toward a lower end
thereof. A rear surface 366R of the first outer blade part 366
extends perpendicular to the top surface of the main plate 344. As
shown in FIG. 11, the rear surface 366R of the first outer blade
part 366 is contiguous with the rear surface 364R of the first
inner blade part 364. The thickness of the first inner blade part
364 in the front-rear direction relative to the rotational
direction R is constant between an upper end and a lower end
thereof.
[0067] As shown in FIG. 12, the second blade 348 is divided into a
second inner blade part 368 and a second outer blade part 370. The
second inner blade part 368 extends radially outward from the
radially inner periphery of the projection part 352. The second
outer blade part 370 extends radially outward from a radially outer
end of the second inner blade part 368 to the radially outer
periphery of the main plate 344.
[0068] In the plan view along the rotational axis of the impeller
340, the second inner blade part 368 is positioned, relative to the
rotational direction R, in front of a radial reference line N2,
which extends radially and passes through the rotational axis C and
a connection part between the second inner blade part 368 and the
second outer blade part 370. The connection part between the second
inner blade part 368 and the second outer blade part 370
corresponds to a radially inner end of the second outer blade part
370. As shown in FIG. 11, the second outer blade part 370 has a
front surface 370F facing forward and a rear surface 370R facing
rearward relative to the rotational direction R. The radial
reference line N2 may pass the front surface 370F of the second
outer blade part 370 at the radially inner end of the second outer
blade part 370 in some embodiments.
[0069] As shown in FIG. 11, the second inner blade part 368 has a
front surface 368F facing forward and a rear surface 368R facing
rearward relative to the rotational direction R. The front surface
368F and the rear surface 368F extend perpendicular to the top
surface of the main plate 344. An angle formed between the top
surface of the main plate 344 and each of the front surface 368F
and the rear surface 368R may be between 85 to 95 degrees in some
embodiments.
[0070] The front surface 370F of the second outer blade part 370
extends from the top surface of the main plate 344 obliquely
rearward relative to the rotational direction R of the impeller
340. The front surface 370F is contiguous with the front surface
368F of the second inner blade part 368. The front surface 370F
extends linearly between an upper end and a lower end thereof in a
cross-sectional view perpendicular to a longitudinal axis of the
second outer blade part 370. The front surface 370F may be gently
curved in a concave or convex manner in some embodiments.
[0071] Although not illustrated, in a cross-sectional view
perpendicular to the longitudinal axis of the second outer blade
part 370, an angle formed between the front surface 370F of the
second outer blade part 370 and a vertical reference line, which
extends parallel to the rotational axis C and passes the upper end
of the front surface 370F, is acute and continuously increases from
the radially inside toward the radially outside.
[0072] As shown in FIG. 12, in the plan view along the rotational
axis C of the impeller 340, a lower portion of the front surface
370F of a radially outer end of the second outer blade part 370 is
positioned in front of the radial reference line N2 relative to the
rotational direction R. An upper portion of the front surface 370F
of the radially outer end of the second outer blade part 370 is
positioned rearward of the radial reference line N2 relative to the
rotational direction R. As shown in FIG. 11, a radially outer
surface of the second outer blade part 370 is flush with the
radially outer periphery of the main plate 344.
[0073] As shown in FIG. 11, the thickness of the second outer blade
part 370 in the front-rear direction relative to the rotational
direction R (i.e., circumferential direction) gradually increases
from an upper end toward a lower end thereof. A rear surface 370R
of the second outer blade part 370 extends perpendicular to the top
surface of the main plate 344 in a cross-sectional view
perpendicular to the longitudinal axis of the second blade 348. The
rear surface 370R of the second outer blade part 370 is contiguous
with the rear surface 368R of the second inner blade part 368. The
thickness of the second inner blade part 368 in the front-rear
direction relative to the rotational direction R (i.e.,
circumferential direction) is constant between an upper end and a
lower end thereof.
[0074] As shown in FIGS. 11 and 15, the second blade 348 has a low
blade part 356 and a high blade part 358. The low blade part 356
extends radially outward from the radially inner periphery of the
inclined surface 354. The high blade part 358 extends radially
outward from a radially outer end of the low blade part 356. As
shown in FIGS. 11, 15 and 16, the height of the low blade part 356
of the second blade 348 from the main plate 344 is less than that
of the first blade 346 when comparing them to each other at an
equal distance from the rotational axis C. The height of the high
blade part 358 from the main plate 344 is equal to that of the
first blade 346 when comparing them to each other at an equal
distance from the rotational axis C. The low blade part 356 is
formed on the projection part 352 of the main plate 344 only,
whereas the high blade part 358 extends on both the projection part
352 and the flat part 350. Thus, a boundary between the low blade
part 356 and the high blade part 358, which is near a boundary line
B in FIG. 15, is positioned just above the projection part 352. The
height of the low blade part 356 continuously increases moving
radially from the inner end of the low blade part 356 toward the
boundary line B between the low blade part 356 and the high blade
part 358.
[0075] In accordance with the third embodiment, the first blades
346 and the second blades 348 have the same radial length as each
other. Each second blade 348 has the low blade part 356 and the
high blade part 358. Each low blade part 356 is formed near the
central portion of the impeller 340. The height of each low blade
part 356 from the main plate 344 is less than that of each first
blade 346 when comparing them to each other at an equal distance
from the rotational axis C. Each high blade part 358 extends
radially outward from the radially outer end of the corresponding
low blade part 356. The height of each high blade part 358 from the
main plate 344 is equal to that of each first blade 346 when
comparing them to each other at an equal distance from the
rotational axis C. Due to this configuration, the difference
between the amount of the fluid forced by the first blades 346 and
the amount of the fluid forced by the second blades 348 can be
reduced, while increasing the opening area of each opening of the
impeller 340. Accordingly, the pump efficiency of the centrifugal
pump 10 can be improved.
[0076] The height of the low blade part 356 of each second blade
part 348 from the main plate 344 continuously increases moving
radially outward. Thus, the impeller 340 can be easily produced by
using molds.
[0077] The low blade part 356 of each second blade 348 is formed on
the projection part 352 only, whereas the high blade part 356 of
each second blade 348 extends radially over the whole radial length
of the flat part 350. Thus, each second blade 348 has a sufficient
height to pressurize and force the fluid to flow radially outward
on the flat part 350.
[0078] The first blades 346 and the second blades 348 are
alternately arranged in the circumferential direction of the
impeller 340. Thus, the opening area of each opening of the
impeller 340 can be held to be substantially constant in the
circumferential direction of the impeller 340. Further, the
difference between the amounts of the fluid forced by each of the
first blades 346 and the second blades 348 can be decreased.
[0079] As mentioned above, the apparatuses and methods disclosed
herein are not limited to the above-described embodiments. For
example, the centrifugal pump may be used for pumping various
fluids, such as air, water, or the like. The motor may be composed
of a brushed motor. The main plate may have additional blades or
grooves along a lower surface thereof. The projection part may be
omitted, such that the main plate may have a flat top surface
having a circular shape. The height of the low blade part may
increase toward the radially inside.
[0080] The thickness of the thin blade part of each second blade
may gradually increase toward the radial outside. Each second blade
may have a thin blade part and a thick blade part instead of the
first blades.
[0081] The impeller may include a plurality of third blades each
having a low blade part and a high blade part. In such case, the
height of the low blade part of each third blade from the main
plate is lower or higher than that of each second blade when
comparing them to each other at an equal distance from the
rotational axis of the impeller.
[0082] The numbers of the first blades, the second blades, and the
third blades may be different from each other. However, the first
blades, the second blades, and the third blades are preferably
arranged on the main plate in the circumferential direction on the
basis of a repetitive order pattern.
[0083] The blades may not be arranged at regular intervals in the
circumferential direction. However, the blades are preferably
positioned on the main plate on the basis of a predetermined
regularity. For example, in a case where the impeller includes
first blades, second blades, and third blades repeatedly, a first
predetermined circumferential distance between the first blade and
the second blade may be greater than a second predetermined
circumferential distance between the second blade and the third
blade in each repeating unit.
* * * * *