U.S. patent application number 11/604770 was filed with the patent office on 2007-05-31 for pump.
This patent application is currently assigned to AISAN KOGYO KABUSHIKI KAISHA. Invention is credited to Nobuhiro Kato, Mamoru Matsubara, Makoto Nakagawa.
Application Number | 20070122264 11/604770 |
Document ID | / |
Family ID | 38087734 |
Filed Date | 2007-05-31 |
United States Patent
Application |
20070122264 |
Kind Code |
A1 |
Nakagawa; Makoto ; et
al. |
May 31, 2007 |
Pump
Abstract
The pump (10, 110, 210) may comprise a casing (39, 139, 239) and
a substantially disk-shaped impeller (36, 136, 236) that rotates
within the casing. A group of depression-shaped grooves may be
formed on at least one of the front and reverse surfaces of the
impeller and the two casing internal surfaces in opposition to
these surfaces. The depression-shaped grooves may extend from the
center towards the outer periphery of the impeller. When the
impeller rotates, fuel within the clearance between the impeller
and the casing is propelled, within the depression-shaped grooves,
from the center towards the periphery. In this way, forces are
generated in the direction that increases the clearance between the
impeller and the casing. It is preferred that the group of
depression-shaped grooves 38b is formed closely spaced near the
discharge hole 50 (area B), and elsewhere (area C) is formed more
widely spaced. Also, it is preferred that the clearance between the
surface on which the depression-shaped grooves 136c are formed and
the surface 138b in opposition thereto increases from the center of
the impeller towards the outer periphery of the impeller.
Inventors: |
Nakagawa; Makoto; (Obu-shi,
JP) ; Matsubara; Mamoru; (Obu-shi, JP) ; Kato;
Nobuhiro; (Obu-shi, JP) |
Correspondence
Address: |
DENNISON, SCHULTZ & MACDONALD
1727 KING STREET
SUITE 105
ALEXANDRIA
VA
22314
US
|
Assignee: |
AISAN KOGYO KABUSHIKI
KAISHA
|
Family ID: |
38087734 |
Appl. No.: |
11/604770 |
Filed: |
November 28, 2006 |
Current U.S.
Class: |
415/55.1 |
Current CPC
Class: |
F04D 29/188 20130101;
F04D 5/002 20130101; F04D 29/406 20130101; F04D 29/0413
20130101 |
Class at
Publication: |
415/055.1 |
International
Class: |
F04D 5/00 20060101
F04D005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 28, 2005 |
JP |
2005-341956 |
Jan 10, 2006 |
JP |
2006-002734 |
Apr 28, 2006 |
JP |
2006-126268 |
Claims
1. A pump comprising a casing and a substantially disk-shaped
impeller rotating within the casing, wherein a group of concavities
is formed on both front and reverse surfaces of the impeller,
concavities forming each group are repeated in a circumferential
direction of the impeller, a first groove is formed on a first
casing internal surface in opposition to the front surface of the
impeller, the first groove extending from an upstream end to a
downstream end in an area facing one of the groups of concavities
of the impeller, a second groove is formed on a second casing
internal surface in opposition to the reverse surface of the
impeller, the second groove extending from an upstream end to a
downstream end in an area facing the other of the groups of
concavities of the impeller, an intake hole and a discharge hole
are formed in the casing, the intake hole linking the upstream end
of one of the first groove and the second groove with the outside
of the casing, the discharge hole linking the downstream end of the
other of the first groove and the second groove with the outside of
the casing, and a group of depression-shaped grooves is formed in
at least the first and second casing internal surfaces, each
depression-shaped grooves extends from the center towards the outer
periphery while shifting in the direction of rotation of the
impeller, and the group of depression-shaped grooves is
asymmetrically formed with respect to the axis of rotation of the
impeller in accordance with the position of the first and second
grooves.
2. A pump according to claim 1, wherein in the area near the
discharge hole in the casing internal surface and/or in the area
near the intake hole in the casing internal surface, the lift
forces generated on the impeller by the group of depression-shaped
grooves are greater than in other areas.
3. A pump according to claim 1, wherein the group of
depression-shaped grooves is formed only in the area near the
discharge hole and/or in the area near the intake hole.
4. A pump according to claim 3, wherein each depression-shaped
groove forming the group of depression-shaped grooves extends from
the center of the impeller towards the outer periphery of the
impeller in a spiral shape.
5. A pump comprising a casing and a substantially disk-shaped
impeller rotating within the casing, wherein a group of concavities
is formed on both front and reverse surfaces of the impeller,
concavities forming each group are repeated in a circumferential
direction of the impeller, a first groove is formed on a first
casing internal surface in opposition to the front surface of the
impeller, the first groove extending from an upstream end to a
downstream end in an area facing one of the groups of concavities
of the impeller, a second groove is formed on a second casing
internal surface in opposition to the reverse surface of the
impeller, the second groove extending from an upstream end to a
downstream end in an area facing the other of the groups of
concavities of the impeller, an intake hole and a discharge hole
are formed in the casing, the intake hole linking the upstream end
of one of the first groove and the second groove with the outside
of the casing, the discharge hole linking the downstream end of the
other of the first groove and the second groove with the outside of
the casing, in at least one surface from among the front and
reverse surfaces of the impeller and the first and second casing
internal surfaces, depression-shaped grooves are formed so that
fluid in the clearance between the impeller and the casing is
pressurized and a force is generated in the direction that
increases the clearance between the impeller and the casing when
the impeller rotates, and the clearance between the surface on
which the depression-shaped grooves are formed and the surface in
opposition thereto when the impeller is not inclined with respect
to the casing increases from the center of the impeller towards the
outer periphery of the impeller.
6. A pump according to claim 5, wherein one surface from among the
surface in which the depression-shaped grooves is formed and the
surface in opposition thereto is formed as a flat plane, and the
other surface is formed in a tapered shape so that the clearance
with the impeller increases from the center of the impeller towards
the outer periphery of the impeller.
7. A pump according to claim 6, wherein the depression-shaped
grooves extend from the center of the impeller towards the outer
periphery of the impeller in a spiral shape.
8. A pump comprising a casing and a substantially disk-shaped
impeller rotating within the casing, wherein a group of concavities
is formed on both front and reverse surfaces of the impeller,
concavities forming each group are repeated in a circumferential
direction of the impeller, a first groove is formed on a first
casing internal surface in opposition to the front surface of the
impeller, the first groove extending from an upstream end to a
downstream end in an area facing one of the groups of concavities
of the impeller, a second groove is formed on a second casing
internal surface in opposition to the reverse surface of the
impeller, the second groove extending from an upstream end to a
downstream end in an area facing the other of the groups of
concavities of the impeller, an intake hole and a discharge hole
are formed in the casing, the intake hole linking the upstream end
of a pump flow path formed by the groups of concavities, the first
groove, and the second groove with the outside of the casing, the
discharge hole linking the downstream end of the pump flow path
with the outside of the casing, depression-shaped grooves sealed
from the pump flow path are formed on at least one surface from
among the intake hole side impeller surface and the intake hole
side casing internal surface, and depression-shaped grooves sealed
from the pump flow path are formed in neither the discharge hole
side impeller surface nor the discharge hole side casing internal
surface.
9. A pump according to claim 8, wherein a projecting portion is
formed in the discharge hole side casing internal surface as a loop
in the circumferential direction of the impeller.
10. A pump according to claim 9, wherein the depression-shaped
grooves extend from the center of the impeller towards the outer
periphery of the impeller in a spiral shape.
11. A pump according to claim 8, further comprising a motor chamber
provided on the outside of the casing, and a motor housed within
the motor chamber, wherein the motor includes a shaft that rotates,
the discharge hole links the pump flow path and the motor chamber,
a through hole that is penetrated by the motor shaft are formed in
the casing, and one end of the motor shaft is fitted to the
impeller.
12. A pump comprising a casing and a substantially disk-shaped
impeller rotating within the casing, wherein a group of concavities
is formed on both front and reverse surfaces of the impeller,
concavities forming each group are repeated in a circumferential
direction of the impeller, a first groove is formed on a first
casing internal surface in opposition to the front surface of the
impeller, the first groove extending from an upstream end to a
downstream end in an area facing one of the groups of concavities
of the impeller, a second groove is formed on a second casing
internal surface in opposition to the reverse surface of the
impeller, the second groove extending from an upstream end to a
downstream end in an area facing the other of the groups of
concavities of the impeller, an intake hole and a discharge hole
are formed in the casing, the intake hole linking the upstream end
of a pump flow path formed by the groups of concavities, the first
groove, and the second groove with the outside of the casing, the
discharge hole linking the downstream end of the pump flow path
with the outside of the casing, intake hole side depression-shaped
grooves are formed on at least one surface from among the intake
hole side impeller surface and the intake hole side casing internal
surface so that when the impeller rotates fluid is pressurized and
a lift force is generated that acts in the direction to increase
the clearance between the intake hole side impeller surface and the
intake hole side casing internal surface, discharge hole side
depression-shaped grooves are formed on at least one surface from
among the discharge hole side impeller surface and the discharge
hole side casing internal surface so that when the impeller rotates
fluid is pressurized and a lift force is generated that acts in the
direction to increase the clearance between the discharge hole side
impeller surface and the discharge hole side casing internal
surface, and the number and/or shape of the discharge hole side
depression-shaped grooves are determined so that the lift force
generated is smaller than the lift force generated by the intake
hole side depression-shaped grooves, in accordance with the number
and/or shape of the intake hole side depression-shaped grooves.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to Japanese Patent
Application numbers 2005-341956, 2006-2734 and 2006-126268, the
contents of which are hereby incorporated by reference into the
present application.
BACKGROUND OF THE INVENTION 1. Field of the Invention
[0002] The present invention relates to a pump for drawing in a
fluid such as fuel etc., increasing pressure thereof, and
discharging the pressurized fuel.
[0003] 2. Description of the Related Art
[0004] This type of pump normally includes a substantially
disk-shaped impeller and a casing that houses the impeller so that
the impeller can rotate. On both the front and reverse surfaces of
the impeller, a group of concavities is formed. Concavities forming
each group are repeated in the circumferential direction. Circular
arc-shaped grooves extending from an upstream end to a downstream
end are formed in the two casing internal surfaces in the area in
opposition to the groups of concavities on the impeller. The pump
flow path is formed by the. groups of concavities on the impeller
and the circular arc-shaped grooves on the casing. An intake hole
is formed in the casing. The intake hole links the upstream end of
the pump flow path with the outside of the casing. An discharge
hole is formed in the casing. The discharge hole links the
downstream end of the pump flow path with the outside of the
casing. When the impeller rotates within the casing, fluid is drawn
from the intake hole into the pump flow path. Fluid that is drawn
into the pump flow path is pressurized while flowing to the
downstream end of the pump flow path. The pressurized fluid is
expelled outside the casing from the discharge hole.
[0005] In this pump, the pressure acting on the front and reverse
surfaces of the impeller tends to be non-uniform. Also, the
difference in pressure acting on the front and reverse surfaces of
the impeller tends to be non-uniform according to position in the
circumferential direction. For example, fluid is drawn into the
pump flow path within the casing from the intake hole, is
pressurized within the pump flow path, and is expelled from the
discharge hole. At the upstream end of the pump flow path
connecting with the intake hole, fuel is drawn in from one surface
of the impeller, but fuel is not drawn in from the other surface.
Also, at the downstream end of the pump flow path connected to the
discharge hole, fuel is expelled from one surface of the impeller,
but fuel is not expelled from the other surface of the impeller. As
a result, near the intake hole and discharge hole the difference in
pressure acting on the front and reverse surfaces of the impeller
becomes larger. If the difference in pressure acting on the
impeller varies with position in the circumferential direction the
impeller will incline with respect to the axis of the impeller, and
contact between impeller and casing will occur. If the impeller
continues rotating in this condition, the performance of the pump
will be reduced by friction losses and wear.
[0006] Therefore, in the pump disclosed in Japanese Laid-open
Patent Publication No.6-280776, depression-shaped grooves in a
U-shape are formed in both the front and reverse surfaces of the
impeller. In this pump, when the impeller rotates, fluid flows into
these depression-shaped grooves. When the fluid that has flowed
into the depression-shaped grooves is discharged from the
depression-shaped grooves, a component of velocity in the axial
direction of the impeller is produced. Therefore, the fluid that is
discharged from the depression-shaped grooves presses the casing
internal surface in the axial direction. In this way, a force is
generated that acts in the direction to increase the clearance
between the impeller and the casing internal surface, contact
between the impeller and the casing is prevented, and the pump
efficiency is improved. However, it is difficult to prevent
inclination of the impeller by simply forming depression-shaped
grooves in the impeller, and it was not possible to prevent
sufficiently contact between the impeller and the casing.
BRIEF SUMMARY OF THE INVENTION
[0007] It is, accordingly, an object of the present teachings to
provide a pump capable of effectively suppressing contact between
the impeller and the casing.
[0008] In one aspect of the present teachings, a pump may comprise
a casing, and a substantially disk-shaped impeller that rotates
within the casing. A group of concavities may be formed on both
front and reverse surfaces of the impeller. Concavities forming
each group may be repeated in a circumferential direction of the
impeller. A first groove may be formed on a first casing internal
surface in opposition to the front surface of the impeller. The
first groove may extend from an upstream end to a downstream end in
an area facing one of the groups of concavities of the impeller. A
second groove may be formed on a second casing internal surface in
opposition to the reverse surface of the impeller. The second
groove may extend from an upstream end to a downstream end in an
area facing the other of the groups of concavities of the impeller.
An intake hole and a discharge hole may be formed in the casing.
The intake hole may link the upstream end of one of the first
groove and the second groove with the outside of the casing, and
the discharge hole may link the downstream end of the other of the
first groove and the second groove with the outside of the casing.
Therefore, when the impeller rotates, fluid is drawn into the
casing from the intake hole. The fluid drawn into the casing is
pressurized by the impeller, and is expelled outside the casing
from the discharge hole.
[0009] In one aspect of the present teachings, a group of
depression-shaped grooves may be formed in at least the first and
second casing internal surfaces. Each of depression-shaped grooves
may extend from the center towards the outer periphery while
shifting in the direction of rotation of the impeller. The group of
depression-shaped grooves may be asymmetrically formed with respect
to the axis of rotation of the impeller in accordance with the
position of the first and second grooves.
[0010] In this pump, when the impeller rotates, fluid in the
clearance between the impeller and the casing is drawn into the
group of depression-shaped grooves, and propelled from the center
towards the outer periphery. This direction is the same as the
direction of the centrifugal force acting on the fluid in the
clearance between the impeller and the casing. Therefore, when the
impeller rotates, a force that propels the fluid within the group
of depression-shaped grooves from the center towards the outer
periphery is efficiently generated. The fluid that is propelled
from the center towards the outer periphery within the group of
depression-shaped grooves presses on the surface of the casing in
opposition to the impeller, and generates an effective lift force
(i.e., a force acting in the direction to increase the clearance
between the impeller and the casing internal surface) on the
impeller.
[0011] Also, the groups of depression-shaped grooves are formed
asymmetrically in accordance with the position of the first groove
and the second groove formed on the casing internal surfaces. By
forming the group of depression-shaped grooves asymmetrically, it
is possible to vary the magnitude of the lift force generated on
the impeller according to the area on the impeller. By forming the
group of depression-shaped grooves asymmetrically according to the
position of the first groove and the second groove, it is possible
to increase the lift force generated on the impeller in the areas
where the pressure difference is large, and to decrease the lift
force generated on the impeller in the areas where the pressure
difference is small. In this way, it is possible to eliminate the
non-uniformity in the pressure difference between the front and
reverse surfaces of the impeller. In this way, it is possible to
suppress the inclination of the impeller with respect to the axis
of the impeller, and suppress contact between the impeller and the
casing.
[0012] Forming the groups of depression-shaped grooves
asymmetrically may be achieved, for example, by forming areas where
the adjacent grooves are closely spaced and areas where the grooves
are more widely spaced, or forming areas where the length of
grooves is long and areas where the length of grooves is short, or
forming areas where the depth of grooves is deep and areas where
the depth of grooves is shallow, or forming areas where the width
of grooves is wide and areas where the width of grooves is narrow,
or forming areas where there are grooves and areas where there are
none.
[0013] In the above pump, it is preferred that in the area near the
discharge hole in the casing internal surface and/or in the area
near the intake hole in the casing internal surface, the lift
forces generated on the impeller by the group of depression-shaped
grooves are greater than in other areas.
[0014] Fluid is drawn into the casing from the intake hole,
pressurized within the casing and expelled from the discharge hole.
Therefore, near the intake hole and the discharge hole the
difference in pressure acting on the front and reverse surfaces of
the impeller tends to be large. If the group of depression-shaped
grooves is formed so that the lift force generated on the impeller
in the area near the intake hole and/or the discharge hole is
larger than in other areas the pressure difference that varies with
the area can be effectively cancelled out.
[0015] Alternatively, the group of depression-shaped grooves that
generates lift forces on the impeller may be formed in the area
near the discharge hole and/or the area near the intake hole only.
According to this configuration, lift forces act only on the
impeller in the area near the discharge hole and/or in the area
near the intake hole, so it is possible to effectively cancel out
the pressure difference that varies with the area.
[0016] It is preferably that each depression-shaped groove
comprising the group of depression-shaped grooves extends from the
center of the impeller towards the outer periphery in a spiral
shape. By forming the grooves in a spiral shape from the center
towards the outer periphery it is possible to smoothly draw the
fluid into the grooves.
[0017] In another aspect of the present teachings, in at least one
surface from among the front and reverse surfaces of the impeller
and the first and second casing internal surfaces,
depression-shaped grooves may be formed so that fluid in the
clearance between the impeller and the casing is pressurized and a
force is generated in the direction that increases the clearance
between the impeller and the casing when the impeller rotates.
Also, the clearance between the surface on which the
depression-shaped grooves are formed and the surface in opposition
thereto when the impeller is not inclined with respect to the
casing may increase from the center of the impeller towards the
outer periphery of the impeller.
[0018] In this pump, the clearance between the surface on which the
depression-shaped grooves are formed and the surface in opposition
to this surface increases towards the outer periphery of the
impeller. Therefore, even if the impeller inclines slightly, the
outer periphery of the impeller and the casing internal surface
will not contact. On the other hand at the center of the impeller
the clearance between the surface on which the depression-shaped
grooves are formed and the surface in opposition to this surface is
small. The lift force (i.e., force acting in the direction to
increase the clearance between the impeller and the casing)
generated by the fluid within the depression-shaped grooves
increases the smaller the clearance. Therefore, it is possible to
increase the lift force generated by the fluid within the
depression-shaped grooves In this way, it is possible to prevent
large inclination of the impeller, and contact of the impeller and
casing can be suppressed.
[0019] In this pump, it is preferred that one surface from among
the surface in which the depression-shaped grooves is formed and
the surface in opposition thereto is formed as a flat plane, and
the other surface is formed in a tapered shape so that the
clearance with the impeller increases from the center of the
impeller towards the outer periphery of the impeller. According to
this configuration, one surface from among the surface in which the
depression shaped grooves are formed and the surface that is in
opposition to this surface is formed as a flat plane, so processing
of this plane is simple.
[0020] It is preferred that the depression-shaped grooves extend
from the center of the impeller towards the outer periphery in a
spiral shape. Also, the depression-shaped grooves may be formed on
the impeller or on the casing.
[0021] In another aspect of the present teachings, an intake hole
and a discharge hole may be formed in the casing. The intake hole
links the upstream end of a pump flow path formed by the groups of
concavities, the first groove, and the second groove with the
outside of the casing. The discharge hole links the downstream end
of the pump flow path with the outside of the casing.
Depression-shaped grooves sealed from the pump flow path may be
formed on at least one surface from among the intake hole side
impeller surface and the intake hole side casing internal surface,
and depression-shaped grooves sealed from the pump flow path may be
formed in neither the discharge hole side impeller surface nor the
discharge hole side casing internal surface.
[0022] In this type of pump, the force due to the pressure
difference of the fluid in the pump flow path acts in a direction
to press the impeller towards the intake hole side casing internal
surface. In other words, the fluid drawn into the pump flow path is
pressurized as it flows from the upstream side (i.e., intake hole
side) of the pump flow path to the downstream side (i.e., discharge
hole side). Therefore, the fluid in the pump flow path is at a
higher pressure in the discharge hole side than the intake hole
side Therefore, the surface of the discharge hole side of the
impeller is subjected to a higher pressure than the surface of the
intake hole side, so the impeller is subject to a force in the
direction of the intake hole side casing internal surface.
[0023] In this pump, depression-shaped grooves are not formed on
the discharge hole side of the impeller surface or the discharge
hole side of the casing internal surface. Therefore, a lift force
is not generated on the discharge hole side impeller surface; a
lift force is only generated on the intake hole side impeller
surface. The lift force acting on the intake hole side impeller
surface acts in a direction to cancel out the force (i.e., force
acting in the direction to press the impeller towards the intake
hole side casing internal surface) generated by the difference in
pressure of the fluid in the casing. In this way, pressing the
impeller towards and contact with the intake hole side casing
internal surface, is suppressed.
[0024] In this pump, it is preferred that a projecting portion is
formed in the discharge hole side casing internal surface forming a
loop in the circumferential direction of the impeller. If a
projecting portion is formed in the discharge hole side casing
internal surface, even if there is contact between the discharge
hole side casing internal surface and the impeller, the discharge
hole side casing internal surface and the impeller only contact
locally. Therefore, it is possible to reduce the friction losses
when the impeller and casing contact.
[0025] Further, it is preferred that the projecting portion is
positioned to the inside of the pump flow path. By providing the
projecting portion to the inside of the pump flow path it is
possible to suppress leakage of fluid from the pump flow path that
passes the projecting portion and flows into the clearance on the
discharge hole side. In this way, it is possible to efficiently
pressurize of the fluid within the casing, and the pump performance
can be improved.
[0026] Also, this pump may further include a motor chamber provided
on the outside of the casing and a motor housed within the motor
housing. The motor may have a shaft that rotates. In this case, it
is preferred that the discharge hole links the pump flow path and
the motor chamber and a through hole that is penetrated by the
motor shaft are formed in the casing, and one end of the motor
shaft is fitted to the impeller.
[0027] According to this configuration, the impeller is subject to
a force in the direction of the intake bole side casing internal
surface as a result of high pressure fluid that flows backwards
from the motor chamber into the casing via the gap between the
shaft and the through hole. As a result, contact between the
impeller and the discharge hole side casing internal surface is
suppressed. Also, even if the impeller is subject to a force in the
direction of the intake hole side casing internal surface, the lift
force generated by the depression-shaped grooves acts in the
direction to cancel out that force, so contact between the impeller
and the intake hole side casing internal surface is suppressed.
[0028] In another aspect of the present teachings, an intake hole
and a discharge hole may be formed in the casing. The intake hole
may link the upstream end of a pump flow path formed by the groups
of concavities, the first groove, and the second groove with the
outside of the casing. The discharge hole may link the downstream
end of the pump flow path with the outside of the casing. Intake
hole side depression-shaped grooves may be formed on at least one
surface from among the intake hole side impeller surface and the
intake hole side casing internal surface so that when the impeller
rotates fluid is pressurized and a lift force is generated that
acts in the direction to increase the clearance between the intake
hole side impeller surface and the intake hole side casing internal
surface. Discharge hole side depression-shaped grooves may be
formed on at least one surface from among the discharge hole side
impeller surface and the discharge hole side casing internal
surface so that when the impeller rotates fluid is pressurized and
a lift force is generated that acts in the direction to increase
the clearance between the discharge hole side impeller surface and
the discharge hole side casing internal surface. The number and/or
shape of the discharge hole side depression-shaped grooves are
preferably determined so that the lift force generated is smaller
than the lift force generated by the intake hole side
depression-shaped grooves, in accordance with the number and/or
shape of the intake hole side depression-shaped grooves.
[0029] According to this pump also, it is possible to suppress
pressing the impeller towards and contact with the intake hole side
casing internal surface.
[0030] These aspects and features may be utilized singularly or, in
combination, in order to make improved pump. In addition, other
objects, features and advantages of the present teachings will be
readily understood after reading the following detailed description
together with the accompanying drawings and claims. Of course, the
additional features and aspects disclosed herein also may be
utilized singularly or, in combination with the above-described
aspect and features.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a vertical section through a pump according to a
first representative embodiment of the present teachings.
[0032] FIG. 2 is a section through the line II-II in FIG. 1.
[0033] FIG. 3 is a section on the line III-III in FIG. 1.
[0034] FIG. 4 is a view corresponding to the section through the
line II-II in FIG. 1 for a pump according to a second
representative embodiment of the present teachings.
[0035] FIG. 5 is a view corresponding to the section through the
line III-III in FIG. 1 for a pump according to a second
representative embodiment of the present teachings.
[0036] FIG. 6 is a diagram to explain an example of the
depression-shaped grooves formed on the pump casing.
[0037] FIG. 7 is a diagram to explain another example of the
depression-shaped grooves formed on the pump casing.
[0038] FIG. 8 is a section on the line VIII-VIII in FIG. 7.
[0039] FIG. 9 is a section on the line IX-IX in FIG. 7.
[0040] FIG. 10 is a vertical section through a pump according to a
third representative embodiment of the present teachings.
[0041] FIG. 11 is a plan (of the discharge hole side surface) of
the impeller of the pump shown in FIG. 10.
[0042] FIG. 12 is a view to explain the shape of the grooves formed
in the discharge hole side surface of the impeller shown in FIG.
11.
[0043] FIG. 13 is a section showing an enlargement of the pump
according to the third representative embodiment.
[0044] FIG. 14 is a vertical section through a pump according to a
fourth representative embodiment of the present teachings.
[0045] FIG. 15 is a plan view of the impeller of the fourth
representative embodiment viewed from the bottom.
[0046] FIG. 16 is a diagram to explain the shape of the grooves
formed in the bottom surface of the impeller shown in FIG. 15.
[0047] FIG. 17 is a section showing an enlargement of the pump
according to the fourth representative embodiment of the present
teachings.
[0048] FIG. 18 is a section showing an enlargement of the Dump
according to a fifth representative embodiment of the present
teachings.
[0049] FIG. 19 is a plan of the impeller according to the fifth
representative embodiment viewed from the bottom.
[0050] FIG. 20 is a plan showing another example of the
depression-shaped grooves formed in the top surface of the
impeller.
[0051] FIG. 21 is a plan showing another example of the
depression-shaped grooves formed in the top surface of the
impeller.
[0052] FIG. 22 is a plan showing another example of the
depression-shaped grooves formed in the top surface of the
impeller.
[0053] FIG. 23 shows the schematic relationship between the
direction of the depression-shaped grooves and the direction of
flow of the fuel within the clearance.
DETAILED DESCRIPTION OF THE INVENTION
First Representative Embodiment
[0054] A Wesco pump 10 according to a first representative
embodiment of the present teachings is explained with reference to
the drawings. The Wesco pump 10 may be used as fuel pump for an
automobile. The Wesco pump 10 may be utilized within a fuel tank,
being utilized for supplying fuel to an engine of the
automobile.
[0055] As shown in FIG. 1, the Wesco pump 10 includes a motor unit
12 and a pump unit 14. The motor unit 12 has a rotor 18. The rotor
18 includes a shaft 20, a laminated iron core 22 fixed to the shaft
20, a coil (not shown in the drawings) wound around the laminated
iron core 22, and a commutator 24 connected to the ends of the
coil. The shaft 20 is rotatably supported by a housing 16 via
bearings 26, 28. A permanent magnet 30 is fixed to the inside of
the housing 16 so as to surround the rotor 18. Terminals which are
not shown on the drawings are provided on a top cover 32 attached
to the top of the housing 16, to supply electricity to the motor
unit 12. The coil is activated via a brush 34 and the commutator
24, to rotate the rotor 18 and shaft 20.
[0056] The lower part of the housing 16 houses the pump unit 14.
The pump unit 14 includes a substantially disk-shaped impeller 36.
On the top surface of the impeller 36, a group of concavities 3a is
formed along the outer periphery. On the bottom surface of the
impeller 36, a group of concavities 3b is formed along the outer
periphery. A through hole is formed in the center of the impeller
36, connected to the shaft 20 so as to prevent relative
rotation.
[0057] A pump casing 39 that houses the impeller 36 includes a pump
cover 38 and a pump body 40.
[0058] As shown in FIG. 2, a groove 38a is formed in the pump cover
38 in the area in opposition to the group of concavities 36a. The
groove 38a is formed in an approximately C-shape stretching from
the upstream end to the downstream end along the direction of
rotation of the impeller 36. An discharge hole 50 is formed in the
pump cover 38 from the downstream end of the groove 38a to the top
surface of the pump cover 38. The discharge hole 50 links the
interior of the pump casing 39 with the exterior (i.e., the
internal space of the motor unit 12). A first pump flow path 44 is
formed by the group of concavities 36a and the groove 38a. A group
of depression-shaped grooves 38b, 38b, . . . is provided on the
bottom surface of the pump cover 38 centralized in the radial
direction. The group of depression-shaped grooves 38b, 38b, . . .
is described later.
[0059] As shown in FIG. 3, a groove 40a is formed in the pump body
40 in the area in opposition to the group of concavities 36b.
Similar to the groove 38a, the groove 40a is formed in an
approximate C-shape stretching from the upstream end to the
downstream end along the direction of rotation of the impeller 36.
An intake hole 42 is formed in the pump body 40 from the bottom
surface of the pump body 40 to the upstream end of the groove 40a
The intake hole 42 links the interior of the pump casing 39 and the
exterior (i.e., exterior of the Wesco pump 10). A second pump flow
path 46 is formed by the group of concavities 38b and the groove
40a. A group of depression-shaped grooves 40b, 40b, . . . is
provided in the top surface of the pump body 40 centralized in the
radial direction. The group of depression-shaped grooves 40b, 40b,
. . . is described later.
[0060] When the impeller 36 rotates within the pump casing 39, fuel
is drawn in from the intake hole 42 into the pump unit 14 and is
led to the pump flow paths 44, 46. The fuel is pressurized while
flowing along the fuel flow paths 44, 46, and is propelled from the
discharge hole 50 towards the motor unit 12. The fuel propelled
towards the motor unit 12 passes the motor unit 12, and is expelled
to the outside from a discharge port 48 formed in the top cover
32.
[0061] As shown in FIG. 2, the group of depression-shaped grooves
38b, 38b, . . . formed in the pump cover 38 all have the same shape
and size. The depression-shaped grooves 38b extend from near the
center towards the periphery in a curved shape (spiral shape). The
ends of the depression-shaped grooves 38b near the periphery are
shifted in the direction of rotation of the impeller 36 (in the
direction of the arrow A) relative to the ends near the center.
[0062] The interval between adjacent depression-shaped grooves 38b
varies depending on the area in which the grooves are formed. The
depression-shaped grooves 38b, 38b, . . . formed in the area B with
the discharge hole 50 in the center (one end of the area B extends
to the upstream end of the groove 38a) are formed more closely
spaced than the depression-shaped grooves 38b, 38b, . . . formed in
the area C which is the area outside area B. A distance D is
provided between the outer periphery end of the depression-shaped
grooves 38b and the inner edge of the groove 38a. In other words, a
flat plane doughnut shape of width D is formed between the outer
periphery ends of the depression-shaped grooves 38b, 38b, . . . and
the inner edge of the groove 38a. The depression-shaped grooves
38b, 38b, . . . and the groove 38a are sealed by this flat
plane.
[0063] As shown in FIG. 3, the group of depression-shaped grooves
40b, 40b, . . . formed in the pump body 40 all have the same shape
and size. The depression-shaped grooves 40b extend from the near
the center towards the periphery in a curved shape (spiral shape).
The ends of the depression-shaped grooves 40b near the periphery
are shifted in the direction of rotation of the impeller 36 (in the
direction of the arrow E) relative to the end near the center.
[0064] The interval between adjacent depression-shaped grooves 40b
varies depending on the area in which the grooves are formed. The
depression-shaped grooves 40b, 40b, . . . formed in the area F with
the downstream end of the groove 40a in the center (one end of the
area F extends to the intake hole 42) are formed more closely
spaced than the depression-shaped grooves 40b, 40b, . . . formed in
the area G which is the area outside area F. A distance H is
provided between the outer periphery end of the depression-shaped
grooves 40b and the inner edge of the groove 40a. In other words, a
flat plane doughnut shape of width H is formed between the outer
periphery ends of the depression-shaped grooves 40b, 40b, . . . and
the inner edge of the groove 40a.
[0065] In the Wesco pump 10 according to the present representative
embodiment, a group of depression-shaped grooves 38b, 38b. . . and
a group of depression-shaped grooves 40b, 40b, . . . are formed in
the pump cover 38 and the pump body 40 respectively. When the
impeller 36 rotates the fuel in the clearance between the impeller
36 and the pump casing 39 is drawn into the group of
depression-shaped grooves 38b, 38b, . . . and the group of
depression-shaped grooves 40b, 40b. . . The outer ends of the
depression-shaped grooves 38b, 40b are shifted in the direction of
rotation of the impeller 36 relative to the inner ends. Therefore,
when the impeller 36 rotates, the direction of the viscous forces
that draws the fuel into the depression-shaped grooves 38b, 40b
acts from the center of the impeller 36 towards the Outer
periphery. This direction is the same as the direction of the
centrifugal force acting on the fuel within the clearance between
the impeller 36 and the pump casing 39 when the impeller 36
rotates.
[0066] Therefore, when the impeller 36 rotates a force is generated
that efficiently propels the fuel within the depression-shaped
grooves 38b, 40b in the direction from the center towards the
periphery. The impeller 36 is pressed from both the top and bottom
surfaces by the fuel propelled from the center towards the outer
periphery within the group of depression-shaped grooves 38b, 38b, .
. . and the group of depression-shaped grooves 40b, 40b, . . . , so
the impeller 36 is maintained between the pump cover 38 and the
pump body 40.
[0067] Also, in the pump cover 38 the group of depression-shaped
grooves 38b, 38b, . . . is closely spaced near the discharge hole
50 (area B), and elsewhere (area C) the group of depression-shaped
grooves 38b, 38b, . . . is more widely spaced. In the pump body 40
the group of depression-shaped grooves 40b, 40b, . . . is closely
spaced near the downstream end of the groove 40a (area F), and
elsewhere (area G) the group of depression-shaped grooves 40b, 40b,
. . . is more widely spaced. In areas B and F where the grooves are
closely spaced, more fuel is propelled from the center to the outer
periphery, so the forces acting on the impeller 36 are greater, and
the difference in pressure on the top and bottom surfaces of the
impeller 36 is cancelled out. In this way it is possible to
suppress the inclination of the impeller 36 with respect to the
axis, and contact between the impeller 36 and the pump casing 39
can be suppressed. Also, in the areas C and G where the grooves are
widely spaced, sealing can be maintained as a result of the large
flat surface. As a result inclination of the impeller 36 can be
suppressed, and leakage of fuel from the pump flow paths can be
reduced.
[0068] In this way, according to the Wesco pump 10 of the present
representative embodiment friction losses and wear can be reduced,
and leakage of fuel from within the pump flow paths can be reduced.
Therefore the performance of the pump can be effectively
improved.
Second Representative Embodiment
[0069] A Wesco pump according to a second representative embodiment
is explained with reference to the drawings. The Wesco pump
according to the second representative embodiment is constituted
similar to the Wesco pump 10 according to the first representative
embodiment, and differs from the first representative embodiment
only in the configuration of the groups of depression-shaped
grooves formed on the pump casing. Here only the points of
difference between the second representative embodiment and the
first representative embodiment are explained, explanation of
common points is omitted.
[0070] As shown in FIG. 4, a group of depression-shaped grooves
68b, 68b, . . . formed on a pump cover 68 extends from the center
towards the periphery in curved lines. The ends of the
depression-shaped grooves 68b near the periphery are shifted in the
direction of rotation of the impeller 36 (the direction of arrow J)
relative to the ends near the center. The spacings between adjacent
depression-shaped grooves 68b, 68b. . . are all equal.
[0071] There are two types of shape for the depression-shaped
grooves 68b, 68b, . . . The length of the group of
depression-shaped grooves 68b1, 68b1, . . . formed in the area K
with an discharge hole 50a at the center (one end of area K extends
to the upstream end of a groove 68a), is longer than the length of
the group of depression-shaped grooves 68b2, 68b2, . . . formed in
the area L, the area other than the area K, so the ends near the
outer periphery are positioned closer to the periphery. In other
words, the distance M between the ends of the depression-shaped
grooves 68b1 near the periphery and the inner edge of the groove
68a is shorter than the distance N between the ends of the
depression-shaped grooves 68b2 near the periphery and the inner
edge of the groove 68a. A flat surface is formed in the area
between the ends of the group of depression-shaped grooves 68b,
68b, . . . near the periphery and the inner edge of the groove
68a.
[0072] As shown in FIG. 5, a group of depression-shaped grooves
70b, 70b, . . . formed on a pump cover 70 extends from near the
center towards the periphery in curved lines. The ends of the
depression-shaped grooves 70b near the periphery are shifted in the
direction of rotation of the impeller 36 (the direction of arrow P)
relative to the ends near the center. The spacings between adjacent
depression-shaped grooves 70b, 70b, . . . are all equal.
[0073] There arc two types of shape for the depression-shaped
grooves 70b, 70b, . . . The length of the group of
depression-shaped grooves 70b1, 70b1, . . . formed in the area Q
with the downstream end of a groove 70a in the center (one end of
the area Q extends to an intake hole 40a) is longer than the length
of the group of depression-shaped grooves 70b2, 70b2, . . . formed
in the area R, the area other than the area Q, so the ends near the
outer periphery are positioned closer to the periphery. In other
words, the distance S between the ends of the depression-shaped
grooves 70b1 near the periphery and the inner edge of the groove
70a is shorter than the distance T between the ends of the
depression-shaped grooves 70b2 near the periphery and the inner
edge of the groove 70a. A flat surface is formed in the area
between the ends of the depression-shaped group of grooves 70b,
70b, . . . near the periphery and the inner edge of the groove
70a.
[0074] In the Wesco pump according to the second representative
embodiment, as for the Wesco pump 10 according to the first
representative embodiment, the group of depression-shaped grooves
68b, 68b, . . . and the group of depression-shaped grooves 70b,
70b, . . . are formed in the pump cover 68 and the pump body 70
respectively. In the pump cover 68, the group of depression-shaped
grooves 68b1, 68b1, . . . near the discharge hole 50a (area K) are
long, and the depression-shaped group of grooves 68b2, 68b2, . . .
formed in the other area (area L) are short. In the pump body 70
the group of depression-shaped grooves 70b1, 70b1, . . . near the
downstream end of the groove 70a (area Q) are long, and the group
of depression-shaped grooves 70b2, 70b2, . . . in the other area
(area R) are short. In areas K and Q where the grooves are formed
longer, more fuel is propelled from the center towards the
periphery, so the difference in pressure applied to the top and
bottom surfaces of the impeller 36 is cancelled out. In this way it
is possible to suppress the inclination of the impeller 36 with
respect to the axis, and contact between the impeller 36 and the
pump casing 68, 70 can be suppressed. Also, in the areas L and R
where the grooves are formed short, sealing can be maintained as a
result of the large flat surface. As a result, leakage of fuel from
the pump flow paths can be reduced.
[0075] In both the first and second representative embodiments
described above, depression-shaped grooves 38b, 40b, 68b, 70b are
formed in both the areas B, F, K, Q near the intake hole and
discharge hole and in the other areas C, G, L, R. However, the
present teachings are not limited to this type of configuration.
For example, depression-shaped grooves may be formed in the areas
near the intake hole and discharge hole to generate forces to
cancel out the difference in pressure on the top and bottom
surfaces of the impeller as much as possible, but in the other
areas the depression-shaped grooves may be omitted. This is because
in the areas apart from the areas near the intake hole and
discharge hole, the difference in pressure applied to the top and
bottom surfaces is very small. By forming groups of
depression-shaped grooves only near the intake hole and discharge
hole the sealing is further improved, and leakage of fuel from the
pump flow paths is effectively reduced.
[0076] Also, it is possible to obtain similar effects by varying
the shape of the depression-shaped grooves (for example, groove
width, groove depth, inflow angle) (see Table 1). For example, as
shown in FIG. 6, in area B where the difference in pressure on the
top and bottom surface of the impeller is large the width of the
depression-shaped groove 88b can be increased, and in area C where
the pressure difference is small the width of the depression-shaped
groove 88b can be decreased. Or, as shown in FIGS. 7 through 9, in
area B where the difference in pressure on the top and bottom
surface of the impeller is large, the depth t2 of the
depression-shaped groove 98b can be increased (see FIG. 9), and in
area C where the pressure difference is small the depth t1 of the
depression-shaped groove 98b can be decreased (see FIG. 8).
Furthermore, in the area where the difference in pressure of the
top and bottom surfaces of the impeller is large the inflow angle
can be made an acute angle, and in the area where the difference in
pressure of the top and bottom surfaces of the impeller is small
the inflow angle can be made an obtuse angle. TABLE-US-00001 TABLE
1 Large pressure Small pressure difference difference Number of
grooves Many Few Groove length Long Short Groove width Large Small
Groove depth Deep Shallow Inflow angle Acute angle Obtuse angle
[0077] Also, in the first and second representative embodiments,
depression-shaped grooves are formed in both the pump cover and
pump body, but depression-shaped grooves may be formed in either
one of the pump cover or the pump body. This is because depending
on the type of fluid pressurized by the Wesco pump and the
configuration of the intake hole and discharge hole, and the like,
forming the depression-shaped grooves in only one of either the
pump cover or pump body can suppress the inclination of the
impeller.
[0078] It is possible to select the number, length, cross-sectional
shape of the depression-shaped grooves as appropriate.
Third Representative Embodiment
[0079] A Wesco pump 110 according to a third representative
embodiment of the present teachings is explained with reference to
the drawings. The Wesco pump 110 according to the third
representative embodiment has a configuration that is substantially
similar to the configuration of the Wesco pump 10 in the first
representative embodiment. However, the third representative
embodiment differs from the Wesco pump 10 according to the first
representative embodiment in that groups of depression-shaped
grooves are formed on the impeller, and the clearance between the
impeller and the pump casing varies in the radial direction Here
the points of difference with the first representative embodiment
are explained in detail and the points in common with the first
representative embodiment are omitted.
[0080] As shown in FIG. 10, the Wesco pump 110 includes a motor
unit 112 and a pump unit 114. The motor unit 112 has the same
configuration as the motor unit 12 of the Wesco pump 10 according
to the first representative embodiment. The pump unit 114 includes
a substantially disk-shaped impeller 136 and a pump casing 139 that
houses the impeller 136.
[0081] As shown in FIG. 11, a D-shaped through hole 138f is formed
in the center of the impeller 136. The through hole 138f is fitted
to the bottom end of the shaft 120. Therefore, the impeller 136 can
move in the axial direction of the shaft 120, but cannot rotate
relative to the shaft 120. Thus, when the shaft 120 rotates the
impeller 136 also rotates.
[0082] The top and bottom surfaces of the impeller 136 are formed
as planes substantially perpendicular to the shaft 120. On the top
surface of the impeller 136, a group of concavities 136a, 136a, . .
. is formed along the periphery, and a group of depression-shaped
grooves 136c, 136c, . . . is provided in the central part in the
radial direction of the impeller 136. On the bottom surface of the
impeller 136, a group of concavities 136b, 136b, . . . is formed
along the periphery, and a group of depression-shaped grooves 136d,
136d, . . . is provided in the central part in the radial
direction. Each of the group of concavities 136a, 136a, . . .
formed in the top surface of the impeller 136 and each of the group
of concavities 136b, 136b, . . . formed in the bottom surface are
linked at the bottom of the concavities.
[0083] As shown in FIGS. 11 and 12, the depression-shaped grooves
136c formed in the top surface of the impeller 136 extend from
their end 137c near the center to their end 137a near the periphery
in a curved shape (spiral shape). Also, a distance A is provided
between the end 137a of the depression-shaped grooves 136c and the
concavities 136a. In other words, a flat plane is formed between
the ends 137a, 137a, . . . of the group of depression-shaped
grooves 136c, 136c, . . . near the periphery and the group of
concavities 136a, 136a, . . . Furthermore, a flat plane is also
formed between the group of concavities 136a, 136a, . . . and
surface of the periphery 136e of the impeller 136.
[0084] Although not shown on the drawings, the depression-shaped
grooves 136d formed in the bottom surface of the impeller 136 are
configured in the same way as the depression-shaped grooves 136c on
the top surface as described above. Also, a flat plane is formed
between the ends of the outer periphery of the depression-shaped
group of grooves 136d and the group of concavities 136b.
Furthermore, a flat plane is also formed between the group of
concavities 136b, 136b, . . . and surface of the periphery 136e of
the impeller 136.
[0085] The pump casing 139 includes a pump cover 138 and a pump
body 140. A taper is formed on the casing surface 138b of the pump
cover 138 so that the clearance with the impeller 136 increases
from the center of the impeller 136 towards the periphery of the
impeller 136. A groove 138a is formed in the casing surface 138b in
opposition to the group of concavities 136a provided in the top
surface of the impeller 136. A taper is also formed on the casing
surface 140b of the pump body 140 so that the clearance with the
impeller 136 increases from the center of the impeller 136 towards
the periphery of the impeller 136. A groove 140a is formed in the
casing surface 140b in opposition to the group of concavities 136b
provided in the bottom surface of the impeller 136. The grooves
138a and 140a are formed in an approximate C-shape from the
upstream end to the downstream end along the direction of rotation
of the impeller 136. The upstream end of the groove 140a is formed
to that it links with the intake hole 142 in the pump body 140. The
downstream end of the groove 138a is formed to that it links with
the discharge hole 150 in the pump cover 138. A first pump flow
path 144 is formed by the group of concavities 136a formed in the
top surface of the impeller 136 and the groove 138a formed in the
pump cover 138. A second pump flow path 146 is formed by the group
of concavities 136b formed in the bottom surface of the impeller
136 and the groove 140a formed in the pump body 140. In FIGS. 10
and 13, the taper angle on the casing surface 138b and the casing
surface 140b has been magnified for ease of viewing. In reality the
taper angle of the casing surface 138b and the casing surface 140b
is very small.
[0086] When the impeller 136 rotates within the pump casing 139,
fuel is drawn into the pump unit 114 from the intake hole 142 and
is led into the pump flow paths 144, 146. The fuel that is
pressurized while flowing through the pump flow paths 144, 146 is
propelled from the discharge hole 150 towards the motor unit 112.
The fuel that is propelled towards the motor unit 112 passes the
motor unit 112, and is propelled to the outside from a discharge
port 148 formed in a top cover 132.
[0087] When the impeller 136 rotates, the fuel in the clearance
between the impeller 136 and the pump casing 138, 140 is drawn into
the group of depression-shaped grooves 136c, 136c, . . . and the
group of depression-shaped grooves 136d, 136d, . . . The fuel that
is drawn into the depression-shaped grooves 136c, 136c, . . . is
guided by the wall 137b on one side of the depression-shaped
grooves 136c, 136c, . . . , and flows towards the end 137a near the
outer periphery of the depression-shaped grooves 136c, 136c, . . .
(refer to FIG. 12). Likewise on the bottom surface of the impeller
136, the fuel is drawn into the group of depression-shaped grooves
136d, 136d. . . , and flows within the depression-shaped grooves
136d, 136d, . . . towards the ends near the outer periphery. The
fuel that is propelled from the center towards the outer periphery
within the depression-shaped grooves 136c, 136c, . . . and the
depression-shaped grooves 136d, 136d, . . . pressurizes the casing
surface 136b and the casing surface 140b, and generates a lift
force on the impeller 136 (i.e., a force in the direction that
increases the clearance with the casing surface 138b and with the
casing surface 140b). Contact between the impeller 136 and the
casing surface 138b or the casing surface 140b is prevented by
these lift forces. The lift force acting on the impeller 136
increases as the clearance between the impeller 136 and the pump
casing 138, 140 decreases. In the Wesco pump 110 according to the
present representative embodiment, the casing surfaces 136b, 140b
are formed with a taper so that the clearance with the impeller 136
increases from the center of the impeller 136 towards the outer
periphery of the impeller 136. In other words, in the locations
where the group of depression-shaped grooves 136c, 136c, . . . and
the group of depression-shaped grooves 136d, 136d, . . . are formed
the clearance between the impeller 136 and the pump casing 138, 140
is small. Therefore, a larger lift force acts on the impeller 136.
In this way, it is possible to further reduce friction losses and
wear.
[0088] The following is a detailed explanation of the lift force
that is generated by the groups of depression-shaped grooves 136c,
136c, . . . and 136d, 136d, . . . when the impeller 136 rotates. As
stated above, when the impeller 136 rotates fuel is led from the
intake hole 142 into the pump flow paths 144, 146, and the fuel is
pressurized as it flows in the pump flow paths 144, 146. Therefore,
the further upstream in the pump flow paths 144, 146 the lower the
fuel pressure, and the further downstream in the pump flow paths
144, 146 the higher the fuel pressure. Also, the pump flow paths
144, 146 are formed on the top and bottom surfaces of the impeller
136, so the impeller 136 is subject to a force in the thrust
direction as a result of the pressure difference of the fuel
flowing in the first pump flow path 144 and the second pump flow
path 146. The pressure difference of the fuel flowing in the first
pump flow path 144 and the second pump flow path 146 varies
according to position in the circumferential direction of the
impeller 136. Therefore, the impeller 136 is subject to non-uniform
forces, so the impeller 136 inclines a very small amount On the
other hand, the casing surfaces 138b, 140b of the pump casing 139
are formed with a taper so that the clearance with the impeller 136
increases from the center of the impeller 136 towards the outer
periphery of the impeller 136. Therefore, even though the impeller
136 inclines slightly, the periphery of the impeller 136 does not
contact the casing surfaces 138b, 140b (refer to FIG. 13). Also, if
the impeller 136 inclines slightly, part of the group of
depression-shaped grooves 136c, 136c, . . . (the part on the right
hand side in FIG. 13) approaches the casing surface 138b, and part
of the group of depression-shaped grooves 136d, 136d, . . . (the
part on the left hand side in FIG. 13) approaches the casing
surface 140b. Then at the position where they approach, the
pressure of the fuel in the group of depression-shaped grooves
136c, 136c, . . . and the group of depression-shaped grooves 136d,
136d, . . . increases, so the pressure on the casing surface 138b
and the casing surface 140b increases. This increased pressure acts
in a direction to prevent inclination of the impeller 136, so the
impeller 136 returns to a horizontal attitude. Therefore, even if
the impeller 136 inclines slightly, the impeller 136 tends to
return to the horizontal as a result of the lift forces generated
by the group of depression-shaped grooves 136c, 136d. Therefore,
contact between the impeller 136 and the casing surfaces 138b, 140b
is prevented, and friction losses and wear can be reduced.
[0089] According to the Wesco pump 110 of the present
representative embodiment, the lift force of the impeller 136 is
increased, so it is possible to suppress friction losses and wear.
Also, even if the impeller 136 inclines slightly, contact between
the periphery of the impeller 136 and the casing surfaces 138b,
140b can be prevented. Also, forces that tend to restore the
impeller 136 to the horizontal act on the impeller 136 as a result
of the lift forces generated by the depression-shaped grooves 136c,
136d. In this way it is possible to effectively improve the
performance of the pump.
[0090] Also, in the Wesco pump 110 according to the present
representative embodiment, the group of depression-shaped grooves
136c, 136c, . . . and the group of depression-shaped grooves 136d,
136d, . . . are formed on the impeller 136 that rotates, in order
to generate lift forces on the impeller 136. Therefore, in addition
to centrifugal forces and viscous forces, inertial forces also act
on the fuel within the group of depression-shaped grooves 136c,
136c, . . . and the group of depression-shaped grooves 136d, 136d,
. . . As a result of the synergistic effect of these forces, it is
possible to generate more effective lift forces.
[0091] Also, in the Wesco pump 110 according to the present
representative embodiment, the groups of depression-shaped grooves
136c, 136d extend from near the center of the impeller 136 towards
the outer periphery of the impeller 136 in a curved shape (spiral
shape). Therefore, fuel drawn in can more effectively flow towards
the periphery, and a greater lift force can be obtained.
[0092] In the Wesco pump 110 described above, the group of
depression-shaped grooves 136c, 136d formed in the impeller 136
extend from near the center of the impeller 136 towards the outer
periphery in a curved shape. However, the present teachings are not
limited to this form. The number, length, cross-sectional shape,
and the like of the depression-shaped grooves formed on the
impeller may be selected as appropriate. Also, the groups of
depression-shaped grooves 136c, 136d may be formed on the casing
surfaces 138b, 140b.
[0093] Also, in the present representative embodiment, the casing
surfaces 138b, 140b are formed in a tapered shape so that the
clearance with the impeller 136 increases from near the center of
the impeller 136 towards the outer periphery. However, the present
teachings are not limited to this form. For example, the top and
bottom surfaces of the impeller 136 may be formed in a taper so
that the clearance with the casing surfaces 138b, 140b increases
from near the center of the impeller 136 towards the outer
periphery.
Fourth Representative Embodiment
[0094] A Wesco pump 210 according to a fourth representative
embodiment is explained with reference to the drawings. The Wesco
pump 210 according to the fourth representative embodiment is
substantially similar to the Wesco pump 10 according to the first
representative embodiment. However, the Wesco pump in the fourth
representative embodiment differs from the Wesco pump 10 in the
first representative embodiment in that a group of
depression-shaped grooves is formed only in the bottom surface of
the impeller, and the clearance between the top surface of the
impeller and the pump casing varies in the radial direction. Here
the points of difference with the first representative embodiment
are explained in detail, and the explanation of the points in
common with the first representative embodiment are omitted.
[0095] As shown in FIG. 14, the Wesco pump 210 includes a motor
unit 212 and a pump unit 214. The motor unit 212 is configured in
the same way as the motor unit 12 of the Wesco pump 10 according to
the first representative embodiment. The pump unit 214 includes a
substantially disk-shaped impeller 236 and a pump casing 239 that
houses the impeller 236.
[0096] The top and bottom surfaces of the impeller 236 are formed
in a plane shape substantially normal to a shaft 220. In the top
surface of the impeller 236, a group of concavities 236b, 236b, . .
. is provided continuously in the radial direction along the outer
periphery. In the bottom surface of the impeller 236, a group of
concavities 236a, 236a, . . . is provided continuously in the
radial direction along the outer periphery, and a group of
depression-shaped grooves 236c, 236c, . . . is provided to the
inside of the group of concavities 236a, 236a, . . . extending from
near the center of the impeller 236 towards the outer periphery.
The group of concavities 236b, 236b, . . . formed in the top
surface of the impeller 236 and the group of concavities 236a,
236a, . . . formed in the bottom surface are linked at the bottom
of the concavities.
[0097] As shown in FIGS. 15 and 16, the depression-shaped grooves
236c formed in the bottom surface of the impeller 236 extend from
their end 237c near the center to their end 237a near the periphery
in a curved shape (spiral shape). Also, a distance A is provided
between the end 237a of the depression-shaped grooves 236c near the
periphery and the concavities 236a. In other words, a flat plane is
formed between the ends 237a, 237a, . . . of the group of
depression-shaped grooves 236c, 236c, . . . near the periphery and
the group of concavities 236a, 236a, . . . Furthermore, a flat
plane is also formed between the group of concavities 236a, 236a, .
. . and surface of the periphery 236e of the impeller 236.
[0098] The pump casing 239 includes a pump cover 238 and a pump
body 240. A casing surface 240b of the pump body 240 is formed in a
plane shape parallel to the bottom surface of the impeller 236. A
groove 240a is formed in the casing surface 240b in opposition to
the group of concavities 236a, 236a, . . . provided in the bottom
surface of the impeller 236. A casing surface 238b of the pump
cover 238 is formed so that a part of the casing surface 238b is
closest to the impeller 236, as shown in FIG. 17. The part
(projecting portion 238c) that is closest to the impeller 236 is
formed as a continuous loop in the circumferential direction. A
groove 238a is formed in the casing surface 238b in opposition to
the group of concavities 236b, 236b, . . . provided in the top
surface of the impeller 236. The grooves 238a and 240a are formed
in an approximate C-shape from the upstream end to the downstream
end along the direction of rotation of the impeller 236. The
upstream end of the groove 240a is formed to that it links with an
intake hole 42 in the pump body 240 The downstream end of the
groove 238a is formed to that it links with a discharge hole 250
formed in the pump cover 238. A first pump flow path 244 is formed
by the group of concavities 236b formed in the top surface of the
impeller 236 and the groove 238a formed in the pump cover 238. A
second pump flow path 246 is formed by the group of concavities
236a formed in the bottom surface of the impeller 236 and the
groove 240a formed in the pump body 240.
[0099] When the impeller 236 rotates within the pump casing 239,
fuel is drawn into the pump unit 214 from the intake hole 242. Fuel
drawn into the pump unit 214 flows from the upstream side to the
downstream side of the pump flow paths 244, 246. Also, while the
fuel is flowing in the pump flow paths 244, 246, the fuel pressure
is increased. When the fuel flowing in the pump flow paths 244, 246
reaches the downstream end of the pump flow path 244, the fuel is
expelled from the discharge hole 250 to the motor unit 212. The
fuel that is propelled towards the motor unit 212 passes the motor
unit 212, and is propelled to the outside from an discharge port
248.
[0100] Here, the forces acting on the impeller 236 when the
impeller 236 rotates are explained. As stated above, when the
impeller 236 rotates, the fuel is pressurized as it flows from the
upstream side to the downstream side of the pump flow paths 244,
246. While the impeller 236 is rotating, the pressure of the fuel
in the pump flow path 244 becomes higher than the pressure of the
fuel in the pump flow path 246. The pump flow paths 244, 246 are
formed in the top and bottom surfaces of the impeller 236, so the
impeller 236 is subject to a force as a result of the difference in
pressure of the fuel flowing in the first pump flow path 244 and
the second pump flow path 246. In other words, as a result of the
difference in pressure of the fuel flowing in the pump flow paths
244, 246, the impeller 236 is subject to a force that presses the
impeller 236 towards the casing surface 240b.
[0101] Also, a minute amount of the fuel expelled from the pump
unit 214 into the motor unit 212 flows into the clearance between
the top surface of the impeller 236 and the casing surface 238b
through the gap between the shaft 220 and a bearing 228. The
pressure of the minute amount of fuel that has flowed into this
clearance is high, so a force is applied to the impeller 236 in the
direction of the casing surface 240b as a result of the pressure of
this fuel.
[0102] Also, a minute amount of fuel flows into the clearance
between the bottom surface of the impeller 236 and the casing
surface 240b. Fuel that has flown into the clearance is drawn into
the group of depression-shaped grooves 236c, 236c, . . . The fuel
drawn into the depression-shaped grooves 236c, 236c, . . . is
guided by one wall 237b of the depression-shaped grooves 236c,
236c, . . . and flows towards the end 237a of the depression-shaped
grooves 236c, 236c, . . . near the outer periphery (refer to FIG.
16). The fuel within the depression-shaped grooves 236c, 236c, . .
. that is propelled from near the center towards the outer
periphery presses against the casing surface 240b, generating a
lift force on the impeller 236 (i.e., a force acting in the
direction to increase the clearance between the impeller 236 and
the casing surface 240b). On the other hand, depression-shaped
grooves are not formed on the top surface of the impeller 236, so
no lift force is generated between the top surface of the impeller
236 and the casing surface 238b.
[0103] In this way, a force as a result of the pressure difference
of the fuel in pump flow paths 244, 246, a force as a result of the
pressure of fuel that has flowed upstream from the motor unit 212
to the pump unit 214 through the gap between the shaft 220 and the
bearing 228, and a force due to the group of depression-shaped
grooves 236c, 236c, . . . act on the impeller 236. The force due to
the pressure difference of the fuel and the force due to the
pressure of the fuel that has flowed upstream act in a direction
that presses the impeller 236 towards the casing surface 240b. The
lift force due to the group of depression-shaped grooves 236c,
236c, . . . acts in a direction to cancel out the forces pressing
the impeller 236 towards the casing surface 240b. Therefore, the
impeller 236 can rotate without being pressed towards the casing
surface 240b. In this way, contact of the impeller 236 with the
casing surface 240b is suppressed, and friction losses and wear can
be reduced.
[0104] As explained above, in the Wesco pump 210, depression-shaped
grooves 236c, 236c, . . . are formed in the bottom surface of the
impeller 236, and depression-shaped grooves are not formed in the
top surface of the impeller 236 and the casing surface 238b.
Therefore, it is possible to cancel out the forces acting to press
the impeller 236 towards the casing surface 240b by the lift forces
generated by the depression-shaped grooves 236c, 236c, . . . In
this way, pressing of the impeller 236 towards the casing surface
240b and contact with the casing surface 240b can be
suppressed.
[0105] Also, in the Wesco pump 210, a projecting portion 238c is
formed in the casing surface 238b to the inside of the group of
concavities 236b, 236b, . . . as a continuous loop in the
circumferential direction of the impeller 236. At the projecting
portion 238c, the clearance with the impeller 236 is smaller than
in other parts, so the flow of fuel leaking from the pump flow path
past the projecting portion 238c into the clearance on the
discharge hole side is suppressed. Therefore, the quantity of fuel
leaking from the pump fuel path 244 can be reduced. In this way,
the fuel within the casing can be efficiently pressurized, and high
pump performance can be achieved.
[0106] Also, even if the force acting on the impeller 236 toward
the casing surface 238b increases due to fluctuations of the fuel
pressure within the pump flow paths 244, 246, contact of the
impeller 236 with the casing surface 240b is suppressed by the
pressure of the fuel that has flowed from the motor unit 212 to the
pump unit 214 through the gap between the shaft 220 and the bearing
228. Also, even assuming the impeller 236 and the casing surface
238b contacted, the impeller 236 will just contact the projecting
portion 238c, so it is possible to minimize and suppress the
friction losses when the impeller and the casing contact.
Fifth Representative Embodiment
[0107] In the Wesco pump 210 according to the fourth representative
embodiment as described above, depression-shaped grooves are only
formed on the bottom surface of the impeller 236, but
depression-shaped grooves may also be formed in the top surface of
the impeller. The following is a description of a Wesco pump 310
according to a fifth representative embodiment, in which
depression-shaped grooves are formed in the top surface of the
impeller. The explanation is either omitted or simplified for parts
that overlap with the fourth representative embodiment.
[0108] The Wesco pump 310 according to the fifth representative
embodiment also includes a motor unit and a pump unit 314. The
motor unit has the same configuration as the Wesco pump 10
according to the first representative embodiment. The pump unit 314
includes a substantially disk-shaped impeller 336 and a pump casing
339 that houses the impeller 336.
[0109] The configuration of the impeller 336 is substantially
similar to the impeller 236 according to the fourth representative
embodiment. That is, a group of concavities 336b, 336b, . . . is
formed in the top surface of the impeller 336. In the bottom
surface of the impeller 336, a group of concavities 336a, 336a, . .
. and a group of depression-shaped grooves 336c, 336c, . . . are
formed.
[0110] Also, a group of depression-shaped grooves 336d, 336d, . . .
is formed in the top surface of the impeller 336. As shown in FIG.
19, the depression-shaped grooves 336d are formed in the same shape
as the depression-shaped grooves 336c formed in the bottom surface
of the impeller 336. That is, the depression-shaped grooves 336d
extend from an end near the center to an end towards the periphery
in a curved shape (spiral shape) However, the number of
depression-shaped grooves 336d is fewer than the number of
depression-shaped grooves 336c (refer to FIGS. 15 and 19).
[0111] The pump casing 339 includes a pump cover 338 and a pump
body 340. A casing surface 340b, groove 340a, and intake hole 342
of the pump body 340 are formed in the same way as those of the
pump body 240 according to the fourth representative embodiment.
The casing surface 338b of the pump cover 338 is formed in a plane
shape parallel to the top surface of the impeller 336, as shown in
FIG. 18. Also, the groove 338a and the discharge hole 350 of the
pump cover 338 are formed in the same way as the pump cover 238
according to the fourth representative embodiment. A first pump
flow path 344 is formed by the group of concavities 336b formed in
the top surface of the impeller 336 and the groove 338a formed in
the pump cover 338. A second pump flow path 346 is formed by the
group of concavities 338a formed in the bottom surface of the
impeller 336 and the groove 340a formed in the pump body 340.
[0112] Here the forces acting on the impeller 336 when the impeller
336 rotates are explained. A force due to the pressure difference
of the fuel flowing in the first pump flow path 344 and the second
pump flow path 346 acts on the impeller 336, as for the fourth
representative embodiment. Also, a force acts as a result of fuel
that flows from the motor unit into the clearance between the top
surface of the impeller 336 and the casing surface 338b through the
gap between the shaft and the bearing. These forces act in a
direction that presses the impeller 336 towards the casing surface
340b.
[0113] Also, the group of depression-shaped grooves 336c, 338c, . .
. formed in the bottom surface of the impeller 336 generates a lift
force B. The lift force B acts in a direction to increase the
clearance between the bottom surface of the impeller 336 and the
casing surface 340b.
[0114] Furthermore, the group of depression-shaped grooves 336d,
336d, . . . formed in the top surface of the impeller 336 generate
a lift force C acting in a direction to increase the clearance
between the top surface of the impeller 336 and the casing surface
338b. As stated above, the number of grooves in the group of
depression-shaped grooves 336d, 336d, . . . is fewer than the
number of grooves in the group of depression-shaped grooves 336c,
336c, . . . Therefore, the lift force C is smaller than the lift
force B.
[0115] In this way, when the impeller 336 rotates, a force due to
the pressure difference of the fuel flowing in the pump flow paths
344, 346, a force due to the pressure of the fuel that has flowed
from the motor unit into the pump casing 339, the lift force B, and
the lift force C act on the impeller 336. The force due to the
pressure difference of the fuel, the pressure of the fuel that has
flowed upstream, and the lift force C act in a direction to press
the impeller 336 towards the casing surface 340b. The lift force B
acts in a direction to cancel out these forces. The lift force B is
larger than the lift force C, so the force obtained by subtracting
the force C from the force B can act to cancel the force due to the
pressure difference of the fuel and force due to the pressure of
the fuel that has flowed upstream. Therefore, contact of the
impeller 336 with the casing surface 340b can be suppressed, and
the impeller 336 can rotate smoothly. In this way, it is possible
to improve the efficiency of the pump.
[0116] Also, if the impeller 336 is pressed against the casing
surface 338b as a result of fluctuations in fuel pressure, the
clearance between the top surface of the impeller 336 and the
casing surface 338b is reduced. Then the fuel in this clearance is
compressed, and the lift force C increases. The impeller 336 is
pressed by the increased lift force C to return to the original
position. Therefore, contact between the impeller 336 and the
casing surface 338b is suppressed.
[0117] In the fifth representative embodiment as described above,
by making the number of grooves in the group of depression-shaped
grooves 336d, 336d, . . . fewer than the number of grooves in the
group of depression-shaped grooves 336c, 336c, . . . the magnitude
of the lift force C (i.e., the force pressing the impeller
downwards) was made smaller than the lift force B (i.e., the force
pressing the impeller upwards). However, the present teachings are
not limited to this form. For example, as shown in FIG. 20, the
length of the depression-shaped grooves 436d in the top surface of
the impeller may be made shorter than the length of the
depression-shaped grooves in the bottom surface of the impeller.
Also, as shown in FIG. 21, the width of the depression-shaped
grooves 536d in the top surface of the impeller may be made smaller
than the width of the depression-shaped grooves in the bottom
surface of the impeller. Or, as shown in FIG. 22, the inflow angle
(in other words, the angle .theta. formed between the
depression-shaped grooves and the direction of flow of fuel within
the clearance (refer to FIG. 23)) of the depression-shaped groove
636d in the top surface of the impeller may be made larger than the
inflow angle of the depression-shaped grooves in the bottom surface
of the impeller. Also, the depth of the depression-shaped grooves
in the top surface of the impeller may be made shallower than the
depth of the depression-shaped grooves in the bottom surface of the
impeller. In this way, by determining the shape of the
depression-shaped grooves on the top surface of the impeller in
accordance with the shape of the depression-shaped grooves on the
bottom surface of the impeller, it is possible to make the lift
force C smaller than the lift force B.
[0118] Also, in each of the representative embodiments described
above, the depression-shaped grooves formed in either the impeller
or in the pump casing extend from near the center of the impeller
towards the outer periphery in a curved shape (spiral shape).
However, the present teachings are not limited to this form. The
number, length, cross-sectional shape of the depression-shaped
grooves formed in the impeller or in the pump casing may be
appropriately designed.
[0119] Finally, although the preferred embodiments have been
described in detail, the present embodiments arc for illustrative
purpose only and not restrictive. It is to be understood that
various changes and modifications may be made without departing
from the spirit or scope of the appended claims. In addition, the
additional features and aspects disclosed herein also may be
utilized singularly or in combination with the above aspects and
features.
* * * * *