U.S. patent application number 16/790893 was filed with the patent office on 2020-08-27 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 | 20200271127 16/790893 |
Document ID | / |
Family ID | 1000004675125 |
Filed Date | 2020-08-27 |
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United States Patent
Application |
20200271127 |
Kind Code |
A1 |
HONDA; Yoshihiko ; et
al. |
August 27, 2020 |
Centrifugal Pump
Abstract
A centrifugal pump includes an impeller rotated about a
rotational axis in a rotational direction by a motor and a housing
defining a pump chamber therein. The impeller is housed in the pump
chamber. The impeller includes a main plate having substantially
circular shape and a first surface extending perpendicular to the
rotational axis. The main plate is provided with a plurality of
blades projecting axially from the first surface and extending
radially along the first surface. Each of the blades has a radially
inner blade part and a radially outer blade part extending radially
outward from the radially inner blade part. Each of the outer blade
parts has a front surface that extends from the main plate
obliquely either frontward or rearward relative to the rotational
direction.
Inventors: |
HONDA; Yoshihiko; (Obu-shi,
JP) ; SUZUKI; Hironori; (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: |
1000004675125 |
Appl. No.: |
16/790893 |
Filed: |
February 14, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 29/28 20130101;
F04D 29/4206 20130101 |
International
Class: |
F04D 29/42 20060101
F04D029/42; F04D 29/28 20060101 F04D029/28 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 21, 2019 |
JP |
2019-029401 |
Claims
1. A centrifugal pump, comprising: an impeller configured to be
rotated in a rotational direction about a rotational axis by a
motor, wherein the impeller includes a main plate and a plurality
of blades, wherein the main plate has a substantially circular
shape and a first surface, wherein each of the blades extends
axially from the first surface of the main plate and radially along
the first surface of the main plate; and a housing defining a pump
chamber that houses the impeller therein, wherein the housing
includes an inlet port configured to supply a fluid into the pump
chamber axially toward a center of the first surface of the main
plate and an outlet port configured to discharge the fluid in a
tangential direction from the pump chamber, wherein: each of the
blades has a radially inner blade part and a radially outer blade
part extending radially outward from the radially inner blade part,
and each of the radially outer blade parts has a front surface that
extends from the main plate obliquely rearward relative to the
rotational direction.
2. The centrifugal pump of claim 1, wherein: an angle of the front
surface of one of the radially outer blade parts relative to a
straight line extending in parallel with the rotational axis is
acute and continuously increases moving radially outward.
3. The centrifugal pump of claim 1, wherein: one of the radially
outer blade parts includes a radially outer end that is divided
into a main plate side part adjacent to the main plate and an
opposite side part positioned away from the main plate, a reference
line passes radially through both the rotational axis of the
impeller and a radially inner end of the one of the radially outer
blade parts, the main plate side part is positioned in front of the
reference line relative to the rotational direction, and the
opposite side part is positioned rearward of the reference line
relative to the rotational direction.
4. The centrifugal pump of claim 1, wherein: a thickness in the
rotational direction of each of the radially outer blade parts
continuously increases moving axially toward the first surface.
5. The centrifugal pump of claim 4, wherein: each of the radially
outer blade parts has a rear surface extending perpendicular to the
main plate or extends obliquely rearward relative to the rotational
direction.
6. A centrifugal pump, comprising: an impeller configured to be
rotated about a rotational axis in a rotational direction by a
motor, wherein the impeller includes a main plate and a plurality
of blades, wherein the main plate has a substantially circular
shape and a first surface, wherein each of the blades projects
axially from the first surface of the main plate and extends
radially along the first surface of the main plate; and a housing
defining a pump chamber that houses the impeller therein, wherein
the housing includes an inlet port configured to supply a fluid
into the pump chamber axially toward a center of the first surface
of the main plate and an outlet port configured to discharge the
fluid from the pump chamber in a tangential direction, wherein:
each of the blades has a radially inner blade part and a radially
outer blade part that extends radially outward from the radially
inner blade part, and each of the radially outer blade parts has a
front surface that extends from the main plate obliquely frontward
relative to the rotational direction.
7. The centrifugal pump of claim 6, wherein: an angle of the front
surface of one of the radially outer blade parts relative to a
straight line extending in parallel with the rotational axis is
acute and continuously increases moving radially outward.
8. The centrifugal pump of claim 6, wherein: one of the radially
outer blade parts includes a radially outer end having a main plate
side part adjacent to the main plate and an opposite side part
positioned away from the main plate, a reference line passes
radially through both the rotational axis of the impeller and a
radially inner end of the one of the radially outer blade parts,
the main plate side part is positioned rearward of the reference
line relative to the rotational direction, and the opposite side
part is positioned in front of the reference line relative to the
rotational direction.
9. The centrifugal pump of claim 6, wherein: a thickness in the
rotational direction of each of the radially outer blade parts
continuously increases moving axially toward the first surface.
10. The centrifugal pump of claim 9, wherein: an outer periphery of
the main plate is curved radially inward between a pair of
circumferentially adjacent blades to define an opening along the
outer periphery of the main plate, and the front surface of the
radially outer blade part of a rear one of the pair of
circumferentially adjacent blades relative to the rotational
direction faces the opening.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to Japanese patent
application serial number 2019-029401, filed Feb. 21, 2019, which
is 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 an
impeller rotated by a motor, and a housing defining a pump chamber
therein. The impeller is housed in the pump chamber and has a main
plate with a circular shape and a plurality of blades radially
extending on a top surface of the main plate. The housing includes
an inlet port and an outlet port in fluid communication with the
pump chamber. The inlet port is formed such that fluid flows into
the pump chamber toward a central portion of the top surface of the
impeller in a direction perpendicular to the top surface of the
main plate of the impeller. The outlet port is formed such that the
fluid is discharged from the pump chamber by rotation of the
impeller in a tangential direction. The housing of the centrifugal
pump includes a partition wall that divides the pump chamber from a
flow passage in the outlet port.
BRIEF SUMMARY
[0005] In one aspect of this disclosure, a centrifugal pump
includes an impeller rotated by a motor in a rotational direction
about a central axis and a housing defining a pump chamber therein.
The impeller is housed in the pump chamber and includes a main
plate having a circular shape and a first surface extending
perpendicular to the central axis. The impeller also includes a
plurality of blades projecting axially from the first surface of
the main plate and extending radially along the first surface. The
housing has an inlet port configured to supply fluid into the pump
chamber axially toward a center of the first surface of the main
plate. The housing also has an outlet port configured to discharge
the fluid by rotation of the impeller in a tangential direction
relative to the central axis. Each of the blades includes a
radially inner blade part and a radially outer blade part that
extends radially outward from the radially inner blade part. The
radially outer blade part of each blade has a leading surface
relative to the rotational direction that extends from the main
plate obliquely either frontward or rearward relative to the
rotational direction.
[0006] In accordance with this aspect, the leading surface of each
radially outer blade part extends from the main plate obliquely
either frontward or rearward in the rotational direction. Due to
this configuration, as each of the radially outer blade parts comes
close to the outlet port, the radially outer blade part gradually
decreases an opening area defined by the outlet port. Thus, a
drastic increase in pressure can be suppressed, thereby offering
the potential to decrease vibration and noise caused by pressure
pulsations in the centrifugal pump.
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 partial cross-sectional view of a first
embodiment of an embodiment of a centrifugal pump in accordance
with the principles described herein.
[0009] FIG. 2 is a cross-sectional view of the centrifugal pump of
FIG. 1 taken along line II-II in FIG. 1.
[0010] FIG. 3 is a perspective view of the impeller of FIG. 1.
[0011] FIG. 4 is a plan view of the impeller of FIG. 1.
[0012] FIG. 5 is a cross-sectional view of the impeller of FIG. 4
taken along line V-V in FIG. 4.
[0013] FIG. 6 is a cross-sectional view of the impeller of FIG. 4
taken along line VI-VI in FIG. 4.
[0014] FIG. 7 is a cross-sectional view of the impeller of FIG. 4
taken along line VII-VII in FIG. 4.
[0015] FIG. 8 is a partial cross-sectional view of a second
embodiment of a centrifugal pump in accordance with the principles
described herein.
[0016] FIG. 9 is a cross-sectional view of the centrifugal pump of
FIG. 8 taken along line IX-IX in FIG. 8.
[0017] FIG. 10 is a perspective view of the impeller in FIG. 8.
[0018] FIG. 11 is a plan view of the impeller of FIG. 8.
[0019] FIG. 12 is a cross-sectional view of the impeller of FIG. 11
taken along line MI-MI in FIG. 11.
[0020] FIG. 13 is a cross-sectional view of the impeller of FIG. 11
taken along line in FIG. 11.
[0021] FIG. 14 is a cross-sectional view of the impeller of FIG. 11
taken along line XIV-XIV in FIG. 11.
[0022] FIG. 15 is a cross-sectional view of a radially outer blade
part of an embodiment of an impeller in accordance with principles
described herein.
[0023] FIG. 16 is a cross-sectional view of a radially outer blade
part of an embodiment of an impeller in accordance with principles
described herein.
DETAILED DESCRIPTION
[0024] One conventional centrifugal pump is disclosed in Japanese
Laid-Open Patent Publication No. 2008-82268. The centrifugal pump
includes blades extending linearly in both a radial direction and
an axial direction relative to the central axis of rotation of the
impeller. Thus, when each blade comes close to the partition wall
dividing the pump chamber from the flow passage in the outlet port,
the pressure of fluid therebetween drastically increases. And, just
after the blade passes near the partition wall, the pressure of
fluid therebetween drastically decreases. Such cyclical pressure
changes may generate pressure pulsations, causing vibration and/or
noise. Therefore, there has been a need for an improved centrifugal
pump.
[0025] 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.
[0026] A first embodiment will be described with reference to FIGS.
1 to 7. In the first embodiment, a centrifugal pump 10 is used as a
purge pump mounted on a vehicle, such as an automobile. The purge
pump is configured to compensate for a shortage of purge gas
flowing from a canister to an air intake passage of an internal
combustion engine. Exemplary coordinate axes are shown in FIGS. 1
and 2 for purposes of further explanation and clarity. However,
these coordinate axes do not limit the orientation or the mounting
direction of the centrifugal pump 10 on the vehicle.
[0027] As shown in FIG. 1, the centrifugal pump 10 of the first
embodiment includes a housing 11 having a substantially a hollow
cylindrical shape. The centrifugal pump 10 also includes a pump
section 12 at an upper portion of the housing 11 and a motor
section 14 positioned below the pump section 12.
[0028] The motor section 14 includes a brushless motor and a
rotational shaft 15 extending in the vertical direction. As will be
described in more detail below, the rotational shaft 15 has a
central axis (also extending in the vertical direction) that
defines a rotational axis of an impeller 30 of centrifugal pump 10.
The motor section 14 may also be referred to herein as a
"motor."
[0029] The housing 11 defines a pump chamber 17 in an upper portion
thereof. The pump chamber 17 may have a hollow short cylindrical
shape and be coaxially aligned with the rotational shaft 15 of the
motor section 14. The housing 11 is divided in the axial direction
into an upper housing member 11a and a lower housing member 11b.
The pump chamber 17 is formed by the upper housing member 11a and
the lower housing member 11b being coupled together. The pump
chamber 17 has a volute part 17a formed at an outer circumference
thereof. The rotational shaft 15 of the motor section 14 penetrates
the lower housing member 11b and protrudes axially into the pump
chamber 17.
[0030] The upper housing member 11a includes an inlet port 20 that
may have a hollow cylindrical shape extending upward from a top
surface of the upper housing member 11a. The inlet port 20 is
coaxially aligned with the pump chamber 17 and the rotational shaft
15. The inlet port 20 defines an inflow passage 20a therein. The
inflow passage 20a provides fluid communication between the inside
and the outside of the pump chamber 17.
[0031] As shown in FIG. 2, the upper housing member 11a of the
housing 11 includes an outlet port 22 that may have a hollow
cylindrical shape extending leftward in FIGS. 1 and 2 from a front
portion of the upper housing member 11a. In the plan view, the
outlet port 22 extends tangentially from the radially outer
perimeter of the pump chamber 17. The outlet port 22 defines an
outflow passage 22a therein. The outflow passage 22a provides fluid
communication between the inside and the outside of the pump
chamber 17. The upper housing member 11a of the housing 11 includes
a partition wall 24 separating and dividing the outflow passage 22a
from the volute part 17a of the pump chamber 17.
[0032] The outlet port 22 includes an upstream open end 22b
positioned at or proximal the volute part 17a of the pump chamber
17. As shown in FIG. 1, in this embodiment, the upstream open end
22b has an elliptical shape with a major axis extending in the
horizontal direction. However, in other embodiments, the upstream
open end 22b may have another shape, such as a rectangular
shape.
[0033] The impeller 30 is rotatably disposed in the pump chamber
17. The impeller 30 is coaxially aligned with the rotational shaft
15 and is fixably mounted to an upper end of the rotational shaft
15 of the motor section 14. Thus, when the rotational shaft 15
rotates about its central, rotational axis, the impeller 30
simultaneously rotates in a rotational direction R about the
central, rotational axis of the shaft 15. In FIG. 2, rotational
direction R is in a clockwise direction. The impeller 30 may be
made from a resin material. As shown in FIG. 1, the inlet port 20
generally faces a central portion of a blade side of the impeller
30 (i.e. a central portion of the top surface side of the impeller
30 in this embodiment).
[0034] When the motor section 14 is driven using electricity
supplied from an external power source, the impeller 30 is rotated
together with the rotational shaft 15, so that fluid, in this
embodiment purge gas, is suctioned into the pump chamber 17 via the
inflow passage 20a of the inlet port 20. The purge gas is
pressurized and then discharged into the outflow passage 22a via
the upstream open end 22b of the outlet port 22 due to the rotation
of the impeller 30. In this manner, the centrifugal pump 10 pumps
the purge gas. When the purge gas is discharged into the upstream
open end 22b of the outlet port 22 via rotation of the impeller 30,
a radially outer end of at least one of the blades 36 of the
impeller 30 passes close to the partition wall 24.
[0035] As shown in FIG. 3, the impeller 30 includes a main plate
32, a boss 34, and a plurality of blades 36 mounted to main plate
32. In this embodiment, twelve blades 36 are provided. The main
plate 32 has substantially a circular plate shape extending
perpendicular to the rotational shaft 15 and the central axis
thereof. The main plate 32 includes a convex part 32a on an upper
surface thereof. The convex part 32a has a truncated cone shape
surrounding the boss 34. The upper surface of the main plate 32 may
also be referred to herein as "a first surface" of the main plate
32. The boss 34 is formed in a hollow cylindrical shape having a
closed top and an open bottom. The boss 34 is coaxially disposed at
a central portion of the upper surface of the main plate 32. As
shown in FIG. 2, the rotational shaft 15 of the motor section 14 is
fixedly inserted into the boss 34. As shown in FIG. 3, each of the
blades 36 protrudes axially upward from the upper surface of the
main plate 32 and extends radially along the upper surface of the
main plate 32. Each of the blades generally has an elongated,
generally rectangular plate shape oriented in the radial
direction.
[0036] In this embodiment, all of the blades 36 may have the same
shape as each other. Accordingly, only one of the blades 36 will be
described for convenience of explanation with the understanding the
other blades 36 are the same. As shown in FIG. 4, a radially inner
end of the blade 36 is coupled to the boss 34 and deviates forward
from a virtual line, which extends between a radially outer end of
the blade 36 and a rotational center 30c of the impeller 30 defined
by the rotational axis of shaft 15. In the plan view of the
impeller 30, an upper edge of the blade 36 gently curves rearward
relative to the rotational direction of the impeller 30 from the
radially inner end toward the radially outer end of the blade 36. A
lower edge of the blade 36 may also be referred to herein as "a
main plate side part" of the blade 26, and the upper edge of the
blade 36 may also be referred to herein as "an opposite side part"
of the blade 26. The plan view illustrated by FIG. 4 corresponds to
"a plan view of the impeller" in this disclosure.
[0037] The blade 36 is divided into a radially inner blade part 37
and a radially outer blade part 38. The radially inner blade part
37 extends radially from the boss 34 to the corresponding radially
outer blade part 38, and the radially outer blade part 38 extends
radially outward from the radially inner blade part 37. In FIG. 4
depicting a plan view of the impeller 30, a radial vector N of the
main plate 32 passes through both the rotation center 30c of the
impeller 30 and a connection part between the inner blade part 37
and the outer blade part 38. The inner blade part 37 is positioned
in front of the radial vector N relative to the rotational
direction R of the impeller 30. A radially outer end of the inner
blade part 37 is contiguous with and coupled to a radially inner
end of the outer blade part 38. The blade 36 includes a front
surface facing forward relative to the direction of rotation R and
a rear surface facing rearward relative to the direction of
rotational R. The radial vector N may pass through the front
surface of the blade 36 at the radially inner end of the outer
blade part 38.
[0038] As shown in FIG. 5, the inner blade part 37 of the blade 36
includes a front surface 37a and a rear surface 37b, each of which
extends perpendicular to the upper surface of the main plate 32
(i.e., axially relative to the rotational axis). In this
disclosure, the term "perpendicular" includes both perpendicular
and substantially perpendicular.
[0039] As shown in FIGS. 6 and 7, a front surface 38a of the outer
blade part 38 of the blade 36 extends from the upper surface of the
main plate 32 obliquely rearward relative to the rotational
direction of the impeller 30. For instance, an angle formed between
the upper surface of the main plate 32 and a lower end of the front
surface 38a of the outer blade part 38 may be oblique. As shown in
FIGS. 3 and 4, the front surface 37a of the inner blade part 37 and
the front surface 38a of the outer blade part 38 are contiguous
with each other. As shown in FIGS. 6 and 7, in the cross-sectional
view perpendicular to a longitudinal direction of the outer blade
part 38, the front surface 38a extends linearly between its upper
end and a lower end in this embodiment. However, in other
embodiments, the front surface 38a may be gently curved in a
concave or convex manner in some embodiments.
[0040] In the cross-sectional view perpendicular to the
longitudinal direction of the outer blade part 38, the front
surface 38a of the outer blade part 38 defines an included angle
380 with a straight line L that extending perpendicular to the
upper surface of the main plate 32 and passing through the upper
end of the front surface 38a. That is, the included angle 380 is
formed by the front surface 38a and the straight line L and is
acute. The included angle 380 between the front surface 38a and the
straight line L gradually increases from the radially inner end
toward the radially outer end of the outer blade part 38. The
direction along which the straight line L is disposed may also be
referred to herein as an "axis disposed in the first
direction.".
[0041] As shown in FIG. 4, in the plan view of the impeller 30, a
lower half of the front surface 38a of the radially outer end of
the outer blade part 38 is positioned in front of the radial vector
N relative to the rotational direction R, and an upper half of this
portion of the front surface 38a is positioned rearward of the
radial vector N relative to the rotational direction R. Such a
configuration is also illustrated in FIGS. 6 and 7, in which a
dashed line N' shows a straight line extending vertically and
perpendicular to the radial vector N. As shown in FIGS. 3 and 4, a
radially outer end surface of the outer blade part 38 is flush with
an outer periphery of the main plate 32. A lower half of the front
surface 38a may also be referred to herein as "a main plate side
part.", and the upper half of the front surface 38a may also be
referred to herein as "an opposite side part". The direction along
which the radial vector N is disposed may also be referred to
herein as a "normal axis."
[0042] As shown in FIGS. 6 and 7, a thickness 38t of the outer
blade part 38 in the rotational direction R gradually increases
from the upper end toward the lower end of the outer blade part 38.
The rear surface 38b of the outer blade part 38 extends
perpendicular to the upper surface of the main plate 32. As shown
in FIG. 3, the rear surface 38b of the outer blade part 38 is
contiguous with the rear surface 37b of the inner blade part 37. As
shown in FIG. 5, a thickness 37t of the inner blade part 37 in the
rotational direction R is constant between an upper end and a lower
end of the inner blade part 37. In this disclosure, the term
"constant" includes both constant and substantially constant.
[0043] In accordance with the first embodiment, the front surface
38a of the outer blade part 38 of each blade 36 extends from the
upper surface of the main plate 32 obliquely rearward relative to
the rotational direction R Thus, as the radially outer end of each
outer blade part 38 comes close to the partition wall 24, the
radially outer end gradually decreases the opening area of the
upstream open end 22b of the outlet port 22. Accordingly, a drastic
increase in pressure can be suppressed, so that vibration and noise
caused by pressure pulsations in the centrifugal pump 10 can be
decreased.
[0044] The included angle 380 between the front surface 38a and the
straight line L gradually increases from the radially inner end
toward the radially outer end of the outer blade part 38. Such
configuration of the front surface 38a can smoothen the fluid flow
outward in the radial direction of the impeller 30.
[0045] As shown in FIG. 4, in the plane view of the impeller 30,
the lower half of the front surface 38a of the radially outer end
of each outer blade part 38 is positioned in front of the radial
vector N in the rotational direction R. Thus, the pressurizing
performance of the centrifugal pump 10 is increased, so that the
number of revolution required for achieving a predetermined
pressure can be decreased. In addition, the upper half of the front
surface 38a of the radially outer end of each outer blade part 38
is positioned rearward of the radial vector N relative to the
rotational direction R. Such configuration can smoothen the fluid
flow outward in the radial direction of the impeller 30 so as to
decrease a load torque on the impeller 30. Accordingly, a decrease
in both the number of revolution of the centrifugal pump 10 and the
load torque on the impeller 30 is achieved, thereby improving pump
efficiency.
[0046] The thickness 38t of each outer blade part 38 gradually
increases from the upper end toward the lower end of the outer
blade part 38. Thus, the rigidity of the outer blade part 38 can be
improved, thereby further reducing vibration and noise.
[0047] The rear surface 38b of each outer blade part 38 extends
upward from the main plate 32 in a direction perpendicular to the
upper surface of the main plate 32. So, when the impeller 30 is
made from a resin material using molds, at least one of the molds,
which shapes the corresponding rear surface 38b, can be removed in
the axial direction of the impeller 30. Accordingly, the molds can
be simplified, thereby improving manufacturing of the impeller
30.
[0048] A second embodiment will be described with reference to
FIGS. 8 to 14. The second embodiment is substantially the same as
the first embodiment described above with some differences
regarding the outer blade parts 38 of the impeller 30. Thus, while
the differences will be described, similar configurations will not
be described in the interest of conciseness.
[0049] As shown in FIGS. 9, 10, and 11, each of the blades 36
includes a radially outer blade part 138 extending radially outward
from the radial outer end of the inner blade part 37. In this
embodiment, all of the outer blade parts 138 have substantially the
same shape as each other. Accordingly, only one radially outer
blade part 138 will be described with the understanding the other
radially outer blade parts 138 are the same. The outer blade part
138 includes a front surface 138a extending from the main plate 32
of the impeller 30 obliquely frontward relative to the rotational
direction R of the impeller 30. As shown in FIG. 12, the inner
blade part 37 of the second embodiment has the same shape as that
of the first embodiment.
[0050] As shown in FIGS. 13 and 14, in the cross-sectional view
perpendicular to the longitudinal direction of the outer blade part
138, an included angle 1380 of the front surface 138a, which is
defined by the front surface 138a and a straight line L that
extends perpendicular to the upper surface of the main plate 32 and
passes through the upper end of the front surface 138a, is acute.
The included angle 1380 formed between the front surface 138a and
the straight line L gradually increases from the radially inner end
toward the radially outer end of the outer blade part 138.
[0051] In FIG. 11, one radial vector N of the boss 34 is shown. The
radial vector N passes through both the rotation center 30c of the
impeller 30 and a connection part between the inner blade part 37
and the outer blade part 138. In the plan view of the impeller 30,
an upper half of the front surface 138a of the radially outer end
of the outer blade part 138 is positioned in front of the radial
vector N relative to the rotational direction R of the impeller 30,
and a lower half of the front surface 138a of the radially outer
end of the outer blade part 138 is positioned rearward of the
radial vector N relative to the rotational direction R.
[0052] As shown in FIGS. 13 and 14, the thickness 138t of the outer
blade part 138 is constant between an upper end and a lower end of
the outer blade part 138. In addition, the thickness 138t is
constant between the radially inner end and the radially outer end
of the outer blade part 138, i.e. over the longitudinal whole
length of the outer blade part 138.
[0053] As shown in FIGS. 10 and 11, an outer periphery of the main
plate 32 is concave and curved radially inward between each pair of
adjacent blades 36, such that the radial length of the main plate
32 gradually decreases from a front of each blade 36 toward the
adjacent blade 36 in a direction opposite to the rotational
direction R. Due to this configuration, the main plate 32 defines a
plurality of circumferentially-spaced openings 140 along the outer
periphery thereof such that each of the front surfaces 138a of the
outer blade part 138 faces a corresponding opening 140.
[0054] In accordance with the second embodiment, the front surface
138a of the outer blade part 138 of each blade 36 of the impeller
30 extends from the upper surface of the main plate 32 obliquely
frontward relative to the rotational direction R of the impeller
30. Thus, as the radially outer end of each outer blade part 138
comes close to the partition wall 24 of the housing 11, which is
illustrated in FIGS. 8 and 9, the radially outer end gradually
decreases the opening area of the upstream open end 22b of the
outlet port 22. Accordingly, a drastic increase in pressure can be
prevented, thereby decreasing vibration and noise caused by
pressure pulsations of the centrifugal pump 10.
[0055] The included angle 1380 formed between the front surface
138a and the straight line L gradually increases from the radially
inner end toward the radially outer end of the outer blade part
138. Such configuration of the outer blade part 138 can smoothen
the fluid flow outward in the radial direction of the impeller
30.
[0056] In the plan view of the impeller 30, the upper half of the
front surface 138a of the radially outer end of each outer blade
part 138 is positioned in front of the radial vector N in the
rotational direction R. Thus, pressurizing performance of the
centrifugal pump 10 is increased, so that the number of revolution
required for achieving a predetermined pressure can be decreased.
In addition, the lower half of the front surface 138a of the
radially outer end of each outer blade part 138 is positioned
rearward of the radial vector N in the rotational direction R. Such
configuration can smoothen the fluid flow outward in the radial
direction of the impeller 30 so as to decrease a load torque on the
impeller 30. Accordingly, a decrease in both the number of
revolution of the centrifugal pump 10 and the load torque on the
impeller 30 is achieved, thereby improving pump efficiency.
[0057] The main plate 32 defines the openings 140 that the front
surfaces 138a of the outer blade parts 138 face. So, when the
impeller 30 is made from a resin material using molds, at least one
of the molds, shaping the corresponding front surface 138a, can be
removed in the axial direction of the impeller 30. Accordingly, the
mold can be simplified, thereby improving manufacturing of the
impeller 30.
[0058] A third embodiment will be described with reference to FIG.
15. The third embodiment is substantially the same as the second
embodiment described above with some modifications regarding the
outer blade parts 138 of the impeller 30. Thus, while the
differences will be described, similar configurations will not be
described in the interest of conciseness.
[0059] As shown in FIG. 15, a radially outer blade part 238 of each
blade 36 includes a front surface 238a formed with a similar
configuration as the front surface 138a of the second embodiment.
However, the outer blade part 238 is also shaped such that its
thickness 238f in the rotational direction R gradually increases
from the upper end toward the lower end of the outer blade part
238. Thus, the rigidity of the outer blade parts 238 can be
increased, thereby reducing vibration and breakage of the outer
blade parts 238.
[0060] A fourth embodiment will be described with reference to FIG.
16. The fourth embodiment is substantially the same as the first
embodiment described above with some modifications regarding the
outer blade parts 38 of the impeller 30. Thus, while the
differences will be described, similar configurations will not be
described in the interest of conciseness.
[0061] As shown in FIG. 16, each radially outer blade part 338 of
the impeller 30 includes a front surface 338a formed with a similar
configuration as the front surface 38a of the first embodiment.
However, the thickness 338t of the outer blade part 338 is constant
between an upper end and a lower end of the outer blade part 338.
That is, a rear surface 338a of each outer blade part 338 faces
obliquely downward relative to the rotational direction R.
[0062] Although not shown in the drawings, an outer periphery of a
main plate 332 is concave and curved radially inward between each
pair of circumferentially adjacent blades 36, such that the radial
length of the main plate 332 gradually increases from a front of
one blade 36 toward an adjacent blade 36. Due to this
configuration, the main plate 332 of the impeller 30 defines a
plurality of circumferentially-spaced openings 340 along the outer
periphery thereof, such that each of the rear surfaces 338b of the
outer blade part 338 faces the corresponding opening 340. Thus,
when the impeller 30 is made from a resin material using molds, at
least one of the molds, shaping the corresponding rear surface
338b, can be removed in the axial direction of the impeller 30.
Accordingly, the molds can be simplified, thereby improving
manufacturing of the impeller 30.
[0063] As mentioned above, the apparatus and methods disclosed in
this application are not limited to the above-described
embodiments. For example, the centrifugal pump 10 may be used for
pumping various fluid, such as air, other than a purge gas. The
brushless motor of the motor section 14 may be replaced with a
brushed motor. The centrifugal pump 10 may be comprised of the
motor section 14 only such that the rotational shaft 15 is rotated
by a driving source that is provided outside the centrifugal pump
10. The impeller 30 may be made from a metal material.
* * * * *