U.S. patent application number 16/326640 was filed with the patent office on 2020-12-03 for electric supercharger.
This patent application is currently assigned to MITSUBISHI HEAVY INDUSTRIES, LTD.. The applicant listed for this patent is MITSUBISHI HEAVY INDUSTRIES ENGINE & TURBOCHARGER, LTD., MITSUBISHI HEAVY INDUSTRIES, LTD.. Invention is credited to Byeongil AN, Yutaka FUJITA, Tadashi KANZAKA, Naomichi SHIBATA, Akihiro SUGIYAMA.
Application Number | 20200378389 16/326640 |
Document ID | / |
Family ID | 1000005051083 |
Filed Date | 2020-12-03 |
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United States Patent
Application |
20200378389 |
Kind Code |
A1 |
SHIBATA; Naomichi ; et
al. |
December 3, 2020 |
ELECTRIC SUPERCHARGER
Abstract
An electric supercharger includes: a compressor impeller; a
motor configured to transmit a driving force to the compressor
impeller via a rotational shaft; a back-surface side casing facing
a back surface of the compressor impeller via a gap and surrounding
the rotational shaft; a bearing disposed between the back-surface
side casing and the rotational shaft so as to support the
rotational shaft rotatably; and a mechanical seal positioned
between the back surface of the compressor impeller and the bearing
in an axial direction of the compressor impeller and configured to
seal a gap between the rotational shaft and the back-surface side
casing.
Inventors: |
SHIBATA; Naomichi;
(Sagamihara-shi, JP) ; AN; Byeongil;
(Sagamihara-shi, JP) ; SUGIYAMA; Akihiro;
(Sagamihara-shi, JP) ; FUJITA; Yutaka; (Tokyo,
JP) ; KANZAKA; Tadashi; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MITSUBISHI HEAVY INDUSTRIES, LTD.
MITSUBISHI HEAVY INDUSTRIES ENGINE & TURBOCHARGER,
LTD. |
Tokyo
Sagamihara-shi, Kanagawa |
|
JP
JP |
|
|
Assignee: |
MITSUBISHI HEAVY INDUSTRIES,
LTD.
Tokyo
JP
MITSUBISHI HEAVY INDUSTRIES ENGINE & TURBOCHARGER,
LTD.
Sagamihara-shi, Kanagawa
JP
|
Family ID: |
1000005051083 |
Appl. No.: |
16/326640 |
Filed: |
March 29, 2017 |
PCT Filed: |
March 29, 2017 |
PCT NO: |
PCT/JP2017/012938 |
371 Date: |
February 19, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 29/284 20130101;
F04D 29/102 20130101; F04D 25/06 20130101; F04D 29/056
20130101 |
International
Class: |
F04D 25/06 20060101
F04D025/06; F04D 29/10 20060101 F04D029/10; F04D 29/28 20060101
F04D029/28; F04D 29/056 20060101 F04D029/056 |
Claims
1. An electric supercharger, comprising: a compressor impeller; a
motor configured to transmit a driving force to the compressor
impeller via a rotational shaft; a back-surface side casing facing
a back surface of the compressor impeller via a gap and surrounding
the rotational shaft; a bearing disposed between the back-surface
side casing and the rotational shaft so as to support the
rotational shaft rotatably; and a mechanical seal positioned
between the back surface of the compressor impeller and the bearing
in an axial direction of the compressor impeller and configured to
seal a gap between the rotational shaft and the back-surface side
casing, wherein the mechanical seal includes: a stationary ring
supported on the back-surface side casing; a rotary ring protruding
from the rotational shaft toward an outer side in a radial
direction of the compressor impeller and facing the stationary ring
so as to be capable of being in contact with the stationary ring in
the axial direction of the compressor impeller, the rotary ring
being configured to rotate with the rotational shaft; and a biasing
member configured to bias one of the rotary ring or the stationary
ring toward the other one of the rotary ring or the stationary
ring, and wherein a groove is formed on a facing surface which is
one of a surface of the rotary ring which faces the stationary ring
or a surface of the stationary ring which faces the rotary
ring.
2. (canceled)
3. The electric supercharger according to claim 1, wherein the back
surface of the compressor impeller has a plurality of ribs disposed
on the back surface at intervals in a circumferential direction of
the compressor impeller.
4. The electric supercharger according to claim 3, wherein each of
the ribs is disposed to so as to extend along a direction which
intersects with the circumferential direction of the compressor
impeller.
5. The electric supercharger according to claim 3, wherein each of
the ribs has an airfoil shape.
6. The electric supercharger according to claim 3, wherein each of
the ribs is disposed so as to extend in a direction inclined from a
radial direction of the compressor impeller such that a radially
outer end of the rib is positioned on an upstream side of a
radially inner end of the rib with respect to a rotational
direction of the compressor impeller.
7. An electric supercharger, comprising: a compressor impeller; a
motor configured to transmit a driving force to the compressor
impeller via a rotational shaft; a back-surface side casing facing
a back surface of the compressor impeller via a gap and surrounding
the rotational shaft; a bearing disposed between the back-surface
side casing and the rotational shaft so as to support the
rotational shaft rotatably; a mechanical seal positioned between
the back surface of the compressor impeller and the bearing in an
axial direction of the compressor impeller and configured to seal a
gap between the rotational shaft and the back-surface side casing;
and between the mechanical seal and the back surface of the
compressor impeller, a rotary part protruding from the rotational
shaft toward an outer side in a radial direction of the compressor
impeller, the rotary part being configured to rotate together with
the rotational shaft.
8. The electric supercharger according to claim 1, further
comprising an abradable coating layer formed on at least a part of
the back surface of the compressor impeller, or at least a part of
a surface of the back-surface side casing which faces the back
surface of the compressor impeller.
9. The electric supercharger according to claim 8, wherein a ratio
G/R of a size G of a gap between the back surface of the compressor
impeller and the back-surface side casing to an outer diameter R of
the compressor impeller is less than 0.5%.
10. The electric supercharger according to claim 1, further
comprising an internal-pressure adjustment mechanism configured to
adjust a pressure inside the back-surface side casing by bringing
into communication an inside and an outside of the back-surface
side casing.
11. The electric supercharger according to claim 7, further
comprising an abradable coating layer formed on at least a part of
the back surface of the compressor impeller, or at least a part of
a surface of the back-surface side casing which faces the back
surface of the compressor impeller.
12. The electric supercharger according to claim 11, wherein a
ratio G/R of a size G of a gap between the back surface of the
compressor impeller and the back-surface side casing to an outer
diameter R of the compressor impeller is less than 0.5%.
13. The electric supercharger according to claim 7, further
comprising an internal-pressure adjustment mechanism configured to
adjust a pressure inside the back-surface side casing by bringing
into communication an inside and an outside of the back-surface
side casing.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to an electric
supercharger.
BACKGROUND ART
[0002] In an engine device of an automobile or the like, to improve
the engine fuel consumption and the efficiency, an exhaust turbine
is driven by exhaust gas discharged from the engine to coaxially
drive a compressor disposed in an intake passage and compress
intake gas supplied to engine, which is called "supercharging".
[0003] In this supercharging using a turbocharger, the torque and
the output during low-speed rotation of the engine may raise
problems, due to response delay during low-speed rotation of the
engine, called turbo lag. A known technique to make up for the
response delay due to turbo lag is a two-stage supercharging system
which includes a turbocharger driven by exhaust gas and an electric
supercharger driven by an electric motor (see Patent Document
1).
CITATION LIST
Patent Literature
[0004] Patent Document 1: JP2015-537162A (translation of a PCT
application)
SUMMARY
Problems to be Solved
[0005] Meanwhile, in an electric supercharger, the compressor is
driven by a motor, unlike a turbocharger. Thus, devices such as a
motor and an inverter substrate are disposed behind the compressor
(between the compressor impeller and the bearing).
[0006] Thus, when a leakage flow passes through the gap between the
back surface of the compressor impeller and the casing and enters
the bearing side, the leakage flow may affect devices such as the
motor and the inverter substrate.
[0007] In particular, in a case where a part of exhaust gas is
recirculated in a two-stage supercharging system including an EGR
and a case where an intermediate cooler is used, and a case where
blow-by gas is returned to the inlet of the compressor, for
instance, air containing condensed water is taken in from the inlet
of the compressor, and thus a leakage flow passing through the gap
between the back surface of the compressor impeller and entering
the bearing side may cause trouble in operation of devices such as
the motor and the inverter.
[0008] Further, in particular, in a case where an electric
supercharger is applied to the high-pressure stage of a two-stage
supercharging system, high-temperature and high-pressure air flows
in from the inlet of the compressor. Thus, a leakage flow passing
through the gap between the back surface of the compressor impeller
and entering the bearing side may cause trouble in operation of
devices such as the motor and the inverter.
[0009] At least one embodiment of the present invention was made in
view of the above conventional problem. An object of at least one
embodiment of the present invention is to provide an electric
supercharger capable of suppressing entry of a leakage flow to the
bearing side via the gap between the back surface of the compressor
impeller and the casing.
Solution to the Problems
[0010] (1) According to at least one embodiment of the present
invention, an electric supercharger includes: a compressor
impeller; a motor configured to transmit a driving force to the
compressor impeller via a rotational shaft; a back-surface side
casing facing a back surface of the compressor impeller via a gap
and surrounding the rotational shaft; a bearing disposed between
the back-surface side casing and the rotational shaft so as to
support the rotational shaft rotatably; and a mechanical seal
positioned between the back surface of the compressor impeller and
the bearing in an axial direction of the compressor impeller and
configured to seal a gap between the rotational shaft and the
back-surface side casing.
[0011] With the above electric supercharger (1), it is possible to
suppress entry of a leakage flow from the gap between the back
surface and the back-surface side casing (hereinafter, referred to
as "back-surface gap") to the bearing by using the mechanical seal,
and suppress inflow of the leakage flow into electric devices such
as the motor. Thus, it is possible to suppress occurrence of
malfunction or the like of the electric devices, and operate the
electric supercharger stably.
[0012] (2) In some embodiment, in the above electric supercharger
(1), the mechanical seal includes: a stationary ring supported on
the back-surface side casing; a rotary ring protruding from the
rotational shaft toward an outer side in a radial direction of the
compressor impeller and facing the stationary ring so as to be
capable of being in contact with the stationary ring in the axial
direction of the compressor impeller, the rotary ring being
configured to rotate with the rotational shaft; and a biasing
member configured to bias one of the rotary ring or the stationary
ring toward the other one of the rotary ring or the stationary
ring. A groove is formed on a facing surface which is one of a
surface of the rotary ring which faces the stationary ring or a
surface of the stationary ring which faces the rotary ring.
[0013] With the above electric supercharger (2), when rotation of
the compressor impeller is stopped, as the biasing member pushes
one of the rotary ring or the stationary ring against the other one
of the rotary ring or the stationary ring, the mechanical seal
functions as a contact seal. Accordingly, it is possible to
suppress entry of a leakage flow from the back-surface gap to the
bearing, and suppress inflow of the leakage flow into electric
devices such as the motor. Thus, it is possible to suppress
occurrence of malfunction or the like of the electric devices, and
operate the electric supercharger stably.
[0014] Further, when the compressor impeller is rotating, the
pressure of gas inside the groove having a pressure increased by a
centrifugal force separates the stationary ring and the rotary ring
against the biasing force of the biasing member. Accordingly, the
stationary ring and the rotary ring separate from each other (not
in contact). Nevertheless, with the pressure of the space on the
inner side of the facing surface being higher than the pressure of
the space on the outer side of the facing surface, it is possible
to suppress entry of a leakage flow from the back-surface gap to
the bearing. Accordingly, it is possible to suppress inflow of the
leakage flow to electric devices such as the motor. Thus, it is
possible to suppress occurrence of malfunction or the like of the
electric devices, and operate the electric supercharger stably.
[0015] (3) In some embodiments, in the above electric supercharger
(1) or (2), the back surface of the compressor impeller has a
plurality of ribs disposed on the back surface at intervals in a
circumferential direction of the compressor impeller.
[0016] With the above electric supercharger (3), by providing the
plurality of ribs, a centrifugal force toward the outer side in the
radial direction is applied to air in the back-surface gap upon
rotation of the compressor impeller, and thereby it is possible to
decrease the pressure of the radially inner part of the
back-surface gap. Accordingly, it is possible to suppress entry of
a leakage flow from the back-surface gap to the bearing, and
suppress inflow of the leakage flow into electric devices such as
the motor. Further, when applied to the above electric supercharger
(2), by reducing the pressure of the radially inner part of the
back-surface gap, it is possible to decrease the spring force of
the biasing member required to move the stationary ring
appropriately, which makes it possible to suppress development of
wear due to friction between the stationary ring and the rotary
ring.
[0017] (4) In some embodiments, in the above electric supercharger
(3), each of the ribs is disposed to so as to extend along a
direction which intersects with the circumferential direction of
the compressor impeller.
[0018] With the above electric supercharger (4), the plurality of
ribs extending in a direction orthogonal to the circumferential
direction rotates with the compressor impeller, and thus it is
possible to apply the centrifugal force toward the outer side in
the radial direction effectively to air in the back-surface gap,
and reduce the pressure of the radially inner part of the
back-surface gap. Accordingly, it is possible to suppress entry of
a leakage flow from the back-surface gap to the bearing, and
suppress inflow of the leakage flow into electric devices such as
the motor.
[0019] (5) In some embodiments, in the above configuration (3) or
(4), each of the ribs has an airfoil shape.
[0020] With the above electric supercharger (5), it is possible to
form an airflow toward the outer side in the radial direction
effectively with the ribs having an airfoil shape, in the
back-surface gap upon rotation of the compressor impeller.
Accordingly, it is possible to suppress entry of a leakage flow
from the back-surface gap to the bearing, and suppress inflow of
the leakage flow into electric devices such as the motor.
[0021] (6) In some embodiments, in the electric supercharger
according to any one of the above (3) to (5), each of the ribs is
disposed so as to extend in a direction inclined from a radial
direction of the compressor impeller such that a radially outer end
of the rib is positioned on an upstream side of a radially inner
end of the rib with respect to a rotational direction of the
compressor impeller.
[0022] With the above electric supercharger (6), with the ribs
being inclined in the above direction, it is possible to suppress
inflow of air into the gaps between the ribs from the outer side in
the radial direction, during rotation of the compressor impeller.
Accordingly, it is possible to suppress entry of a leakage flow
from the back-surface gap to the bearing, and suppress inflow of
the leakage flow into electric devices such as the motor.
[0023] (7) In some embodiments, the electric supercharger according
to any one of the above (1) to (6) further includes, between the
mechanical seal and the back surface of the compressor impeller, a
rotary part protruding from the rotational shaft toward an outer
side in a radial direction of the compressor impeller, the rotary
part being configured to rotate together with the rotational
shaft.
[0024] With the above electric supercharger (7), upon rotation of
the compressor impeller, a centrifugal force toward the outer side
in the radial direction is applied to air in the back-surface gap
in accordance with rotation of the rotary part, and thereby it is
possible to decrease the pressure of the radially inner part of the
back-surface gap. Accordingly, it is possible to suppress entry of
a leakage flow from the back-surface gap to the bearing, and
suppress inflow of the leakage flow into electric devices such as
the motor. Further, when applied to the above electric supercharger
(2), by reducing the pressure of the radially inner part of the
back-surface gap, it is possible to decrease the spring force of
the biasing member required to move the stationary ring
appropriately, which makes it possible to suppress development of
wear due to friction between the stationary ring and the rotary
ring.
[0025] (8) In some embodiments, the electric supercharger according
to any one of the above (1) to (7) further includes an abradable
coating layer formed on at least a part of the back surface of the
compressor impeller, or at least a part of a surface of the
back-surface side casing which faces the back surface of the
compressor impeller.
[0026] With the above electric supercharger (8), in a case where
the abradable coating layer is formed on at least a part of the
back surface of the compressor impeller, the abradable coating
layer would be ground upon rotation of the compressor impeller even
if the abradable coating layer formed on the back surface of the
compressor impeller makes contact with a surface of the
back-surface side casing that faces the back surface of the
compressor impeller. Thus, it is possible to reduce the clearance
between the back surface and the back-surface side casing.
[0027] Furthermore, in a case where the abradable coating layer is
formed on at least a part of a surface of the back-surface side
casing that faces the back surface of the compressor impeller, the
abradable coating layer would be ground upon rotation of the
compressor impeller even if the abradable coating layer formed on a
facing surface of the back-surface side casing that faces the back
surface of the compressor impeller makes contact with the back
surface of the compressor impeller. Thus, it is possible to reduce
the clearance between the back surface and the back-surface side
casing.
[0028] Accordingly, it is possible to promote a pressure decrease
toward the inner side in the radial direction, in the back-surface
gap. Thus, it is possible to reduce the axial-directional pressure
difference between the pressure of the radially inner part and the
pressure near the bearing, of the back-surface gap, and thus it is
possible to suppress entry of a leakage flow toward the bearing
from the back-surface gap. Accordingly, it is possible to suppress
inflow of the leakage flow into electric devices such as the motor
and an inverter. Thus, it is possible to suppress occurrence of
malfunction or the like of the electric devices, and operate the
electric supercharger stably.
[0029] Further, the compressor impeller receives a thrust force
toward the upstream in the intake direction of air, in the axial
direction, when air is compressed. In the above electric
supercharger, it is possible to reduce the pressure in the
back-surface gap for the compressor impeller, and thus it is
possible to reduce the thrust force in the axial direction.
[0030] Further, by promoting the pressure decrease toward the inner
side in the radial direction in the back-surface gap to reduce the
pressure of the radially inner part of the back-surface gap, it is
possible to decrease the spring force of the biasing member
required to move the stationary ring of the mechanical seal
appropriately, which makes it possible to suppress development of
wear due to friction between the stationary ring and the rotary
ring.
[0031] (9) In some embodiments, in the electric supercharger (8), a
ratio G/R of a size G of a gap between the back surface of the
compressor impeller and the back-surface side casing to an outer
diameter R of the compressor impeller is less than 0.5%.
[0032] With the above electric supercharger (9), it is possible to
promote a pressure decrease toward the inner side in the radial
direction, in the back-surface gap, effectively. According to the
inventors of the present invention, when comparing a case where the
abradable coating layer is provided and the ratio C/Ri is set to be
0.8% and a case where the abradable coating layer is not provided
and C/Ri is set to be 0.25%, the former can reduce more pressure of
the radially inner part of the back-surface gap by 26% compared to
the latter.
[0033] (10) In some embodiments, the electric supercharger
according to any one of the above (1) to (9) further includes an
internal-pressure adjustment mechanism configured to adjust a
pressure inside the back-surface side casing by bringing into
communication an inside and an outside of the back-surface side
casing.
[0034] With the above electric supercharger (10), in the electric
supercharger according to any one of the above (1) to (9), even in
a case where the pressure of the radially inner part of the
back-surface gap is low, it is possible to stabilize the pressure
balance across the mechanical seal by adjusting the pressure inside
and outside the back-surface side casing by using the pressure
adjustment mechanism. Accordingly, it is possible to suppress entry
of a leakage flow to the bearings through the back-surface gap
stably with the mechanical seal.
Advantageous Effects
[0035] According to at least one embodiment of the present
invention, it is possible to provide an electric supercharger
capable of suppressing entry of a leakage flow to the bearing side
via the gap between the back surface of the compressor impeller and
the casing.
BRIEF DESCRIPTION OF DRAWINGS
[0036] FIG. 1 is a schematic diagram showing a schematic
cross-sectional view of an electric supercharger 2 according to an
embodiment.
[0037] FIG. 2 is a schematic diagram showing a schematic
cross-sectional view in the vicinity of a back surface 16 of a
compressor impeller 4 of an electric supercharger 2 (2A) according
to an embodiment, showing a configuration example of a mechanical
seal 20.
[0038] FIG. 3 is a view of a compressor impeller 4 in rotation, in
the electric supercharger 2 (2A) depicted in FIG. 2.
[0039] FIG. 4 is a schematic diagram showing a schematic
cross-sectional view in the vicinity of a back surface 16 of a
compressor impeller 4 of an electric supercharger 2 (2B) according
to an embodiment.
[0040] FIG. 5 is a diagram showing a configuration example of the
ribs 44 depicted in FIG. 4, showing an example of arrangement of
the ribs 44 in an axial-directional view.
[0041] FIG. 6 is a diagram showing a configuration example of the
ribs 44 depicted in FIG. 4, showing an example of arrangement of
the ribs 44 in an axial-directional view.
[0042] FIG. 7 is a schematic diagram showing a schematic
cross-sectional view in the vicinity of a back surface 16 of a
compressor impeller 4 of an electric supercharger 2 (2C) according
to an embodiment.
[0043] FIG. 8 is a diagram showing a configuration example of the
rotary part 50 depicted in FIG. 7, showing an example of the shape
of the rotary part 50 in an axial-directional view.
[0044] FIG. 9 is a diagram showing a configuration example of the
rotary part 50 depicted in FIG. 7, showing an example of the shape
of the rotary part 50 in an axial-directional view.
[0045] FIG. 10 is a diagram showing a configuration example of the
rotary part 50 depicted in FIG. 7, showing an example of the shape
of the rotary part 50 in an axial-directional view.
[0046] FIG. 11 is a schematic diagram showing a schematic
cross-sectional view in the vicinity of a back surface 16 of a
compressor impeller 4 of an electric supercharger 2 (2D) according
to an embodiment.
[0047] FIG. 12 is a graph showing the relationship between the
radial-directional position R and the gauge pressure P of the
back-surface gap `g`. The dotted line indicates an electric
supercharger 2 (2A) not including an abradable coating layer 90,
and the solid line indicates an electric supercharger 2 (2D)
including an abradable coating layer 90 formed on the facing
surface 21.
[0048] FIG. 13 is a schematic diagram showing a schematic
cross-sectional view in the vicinity of a back surface 16 of a
compressor impeller 4 of an electric supercharger 2 (2E) according
to an embodiment.
[0049] FIG. 14 is a diagram showing an example of arrangement of a
communication hole 53 that serves as an internal-pressure
adjustment mechanism.
[0050] FIG. 15 is a diagram showing an example of arrangement of a
communication hole 53 that serves as an internal-pressure
adjustment mechanism.
[0051] FIG. 16 is a schematic configuration diagram of an engine
device 100 to which an electric supercharger 2 (2A to 2E) can be
applied preferably.
[0052] FIG. 17 is a schematic diagram showing a schematic
cross-sectional view in the vicinity of a back surface 16 of a
compressor impeller 4 of an electric supercharger 2 (2F) according
to another embodiment.
[0053] FIG. 18 is a schematic diagram showing a schematic
cross-sectional view in the vicinity of a back surface 16 of a
compressor impeller 4 of an electric supercharger 2 (2G) according
to another embodiment.
[0054] FIG. 19 is a schematic diagram showing a schematic
cross-sectional view in the vicinity of a back surface 16 of a
compressor impeller 4 of an electric supercharger 2 (2H) according
to another embodiment.
[0055] FIG. 20 is a schematic diagram showing a schematic
cross-sectional view in the vicinity of a back surface 16 of a
compressor impeller 4 of an electric supercharger 2 (2I) according
to another embodiment.
[0056] FIG. 21 is a schematic diagram showing a schematic
cross-sectional view in the vicinity of a back surface 16 of a
compressor impeller 4 of an electric supercharger 2 (2J) according
to another embodiment.
[0057] FIG. 22 is a schematic diagram showing a schematic
cross-sectional view in the vicinity of a back surface 16 of a
compressor impeller 4 of an electric supercharger 2 (2K) according
to another embodiment.
[0058] FIG. 23 is a schematic configuration diagram of an engine
device 100 to which an electric supercharger 2 (2A to 2K) can be
applied.
DETAILED DESCRIPTION
[0059] Embodiments of the present invention will now be described
in detail with reference to the accompanying drawings. It is
intended, however, that unless particularly identified, dimensions,
materials, shapes, relative positions and the like of components
described in the embodiments shall be interpreted as illustrative
only and not intended to limit the scope of the present
invention.
[0060] For instance, an expression of relative or absolute
arrangement such as "in a direction", "along a direction",
"parallel", "orthogonal", "centered", "concentric" and "coaxial"
shall not be construed as indicating only the arrangement in a
strict literal sense, but also includes a state where the
arrangement is relatively displaced by a tolerance, or by an angle
or a distance whereby it is possible to achieve the same
function.
[0061] For instance, an expression of an equal state such as "same"
"equal" and "uniform" shall not be construed as indicating only the
state in which the feature is strictly equal, but also includes a
state in which there is a tolerance or a difference that can still
achieve the same function.
[0062] Further, for instance, an expression of a shape such as a
rectangular shape or a cylindrical shape shall not be construed as
only the geometrically strict shape, but also includes a shape with
unevenness or chamfered corners within the range in which the same
effect can be achieved.
[0063] On the other hand, an expression such as "comprise",
"include", "have", "contain" and "constitute" are not intended to
be exclusive of other components.
[0064] FIG. 1 is a schematic diagram showing a schematic
cross-sectional view of an electric supercharger 2 according to an
embodiment.
[0065] In an illustrative embodiment depicted in FIG. 1, the
electric supercharger 2 includes a compressor impeller 4, a
rotational shaft 6, an impeller casing 8, bearings 10A, 10B, a
motor 12, a back-surface side casing 14 (stationary member), and a
mechanical seal 20.
[0066] Hereinafter, unless otherwise stated, the circumferential
direction of the compressor impeller 4 is referred to as merely
"circumferential direction", the radial direction of the compressor
impeller 4 is referred to as merely "radial direction", and the
axial direction of the compressor impeller 4 is referred to as
merely "axial direction".
[0067] The impeller casing 8 is formed so as to surround the
compressor impeller 4, and is configured to guide intake air to the
inlet of the compressor impeller 4 and discharge air compressed by
the compressor impeller 4.
[0068] The bearings 10A, 10B are configured as ball bearings that
support the rotational shaft 6 rotatably, and as grease-lubrication
type bearings which contain grease as a lubricating agent sealed
around balls held between an inner race and an outer race which are
not depicted. The bearing 10A is positioned between the mechanical
seal 20 and the motor 12 in the axial direction, and is positioned
between the back-surface side casing 14 and the rotational shaft 6
in the radial direction. The bearing 10B is positioned opposite to
the bearing 10A across the motor 12 in the axial direction, and is
positioned between the back-surface side casing 14 and the
rotational shaft 6 in the radial direction.
[0069] The motor 12 is configured to transmit a driving force to
the compressor impeller 4 via the rotational shaft 6. The motor 12
is positioned between the bearing 10A and the bearing 10B in the
axial direction.
[0070] The back-surface side casing 14 faces the back surface 16 of
the compressor impeller 4 via a gap, and is configured to surround
the mechanical seal 20, the bearings 10A, 10B, and the motor 12.
Further, the back-surface side casing 14 includes an inverter
housing portion 18 for housing an inverter (not depicted), on the
opposite side from the motor 12 across the bearing 10B.
[0071] The mechanical seal 20 is positioned between the back
surface 16 of the compressor impeller 4 and the bearing 10A in the
axial direction, and is configured to seal the gap between the
rotational shaft 6 and the back-surface side casing 14.
[0072] FIG. 2 is a schematic diagram showing a schematic
cross-sectional view in the vicinity of a back surface 16 of a
compressor impeller 4 of an electric supercharger 2 (2A) according
to an embodiment, showing a configuration example of a mechanical
seal 20. FIG. 3 is a view of a compressor impeller 4 in rotation,
in the electric supercharger 2 (2A) depicted in FIG. 2.
[0073] In some embodiments, as depicted in FIGS. 2 and 3, the
mechanical seal 20 includes a stationary ring 22, a rotary ring 24,
and a biasing member 26.
[0074] The stationary ring 22 is formed to have an annular shape
along the circumferential direction, and is supported on the
back-surface side casing 14. The stationary ring 22 is at a
position that is between the rotary ring 24 and the back-surface
side casing 14, and between the back-surface side casing 14 and the
rotational shaft 6.
[0075] The rotary ring 24 is disposed between the back surface 16
of the compressor impeller 4 and the stationary ring 22, and is
configured to have an annular shape along the circumferential
direction so as to face the stationary ring 22 so as to be capable
of being in contact with the stationary ring 22. The rotary ring 24
is configured to protrude toward an outer side from the rotational
shaft 6 in the radial direction, and rotate together with the
rotational shaft 6.
[0076] The biasing member 26 is configured to bias one of the
stationary ring 22 or the rotary ring 24 toward the other one of
the stationary ring 22 or the rotary ring 24. In the depicted
embodiment, the biasing member 26 includes an elastic member (e.g.,
coil spring, disc spring, or rubber), and is interposed between the
stationary ring 22 and the back-surface side casing 14 so as to
bias the stationary ring 22 toward the rotary ring 24.
[0077] Furthermore, a groove 34 is formed on a facing surface 32,
which is one of a surface 28 of the rotary ring 24 that faces the
stationary ring 22, or a surface 30 of the stationary ring 22 that
faces the rotary ring 24 (in the depicted embodiment, the facing
surface 32 is the surface 28 of the rotary ring 24 facing the
stationary ring 22). As depicted in FIG. 2, the groove 34 on the
facing surface 32 is formed so as to be in communication with a
space 36 on the inner side of the facing surface 32 in the radial
direction (space between the stationary ring 22 and the rotational
shaft 6), and so as not to be in communication with the space 38 on
the outer side of the facing surface 32 in the radial direction (of
the back-surface gap `g` between the back surface 16 and the
back-surface side casing 14, the outer portion of the stationary
ring 22), in a state where the stationary ring 22 and the rotary
ring 24 are in contact. That is, in a state where the stationary
ring 22 and the rotary ring 24 are in contact, the groove 34 is
disposed from a position on the inner side, in the radially
direction, of the radially inner end 40 of the contact portion
between the stationary ring 22 and the rotary ring 24 on the facing
surface 32 to a position that does not reach the radially outer end
42 of the contact portion between the stationary ring 22 and the
rotary ring 24, on the facing surface 32.
[0078] With the above configuration, when rotation of the
compressor impeller 4 is stopped, as depicted in FIG. 2, as the
biasing member 26 pushes the stationary ring 22 against the rotary
ring 24, the mechanical seal 20 functions as a contact seal.
Accordingly, it is possible to suppress entry of a leakage flow
from the back-surface gap `g` to the bearing 10A, and suppress
inflow of the leakage flow into electric devices such as the motor
12. Thus, it is possible to suppress occurrence of malfunction or
the like of the electric devices, and operate the electric
supercharger stably.
[0079] Further, when the compressor impeller 4 is rotating, the
pressure of gas inside the groove 34 having a pressure increased by
a centrifugal force pushes the stationary ring 22 into the side of
the biasing member 26, as depicted in FIG. 3. Accordingly, the
stationary ring 22 and the rotary ring 24 separate from each other
(not in contact). Nevertheless, with the pressure of the space 38
on the inner side of the facing surface 32 being higher than the
pressure of the space 38 on the outer side of the facing surface
32, it is possible to suppress entry of a leakage flow from the
back-surface gap `g` to the bearing 10A. Accordingly, it is
possible to suppress inflow of the leakage flow into electric
devices such as the motor 12. Thus, it is possible to suppress
occurrence of malfunction or the like of the electric devices, and
operate the electric supercharger stably.
[0080] Next, some modified examples of the electric supercharger 2
will be described with reference to FIGS. 4 to 13. In the following
modified examples, the same configurations as those of the electric
supercharger 2 (2A) are associated with the same reference numerals
to omit description, and the characteristic configurations of the
respective modified examples will be mainly described.
[0081] FIG. 4 is a schematic diagram showing a schematic
cross-sectional view in the vicinity of a back surface 16 of a
compressor impeller 4 of an electric supercharger 2 (2B) according
to an embodiment. FIG. 5 is a diagram showing a configuration
example of the ribs 44 depicted in FIG. 4, showing an example of
arrangement of the ribs 44 in an axial-directional view. FIG. 6 is
a diagram showing a configuration example of the ribs 44 depicted
in FIG. 4, showing an example of arrangement of the ribs 44 in an
axial-directional view.
[0082] In some embodiments, as depicted in FIGS. 4 to 6, a
plurality of ribs 44 are disposed at intervals in the
circumferential direction, on the back surface 16 of the compressor
4. With the above configuration, by providing the plurality of ribs
44, a centrifugal force toward the outer side in the radial
direction is applied to air in the back-surface gap `g` upon
rotation of the compressor impeller 4, and thereby it is possible
to decrease the pressure of the radially inner part of the
back-surface gap `g`. Accordingly, it is possible to suppress entry
of a leakage flow from the back-surface gap `g` to the bearing 10A,
and suppress inflow of the leakage flow into electric devices such
as the motor. Further, by reducing the pressure of the radially
inner part of the back-surface gap `g`, it is possible to decrease
the spring force of the biasing member 26 required to move the
stationary ring 22 appropriately, which makes it possible to
suppress development of wear due to friction between the stationary
ring 22 and the rotary ring 24.
[0083] In some embodiments, as shown in FIGS. 5 and 6 for instance,
each of the ribs 44 is formed to extend along a direction that
intersects with the circumferential direction. Further, in the
embodiment depicted in FIG. 5, the plurality of ribs 44 are
disposed so as to extend in a radial fashion along a direction
orthogonal to the circumferential direction (radial direction).
[0084] With the above configuration, the plurality of ribs 44
extending in a direction orthogonal to the circumferential
direction rotates with the compressor impeller 4, and thus it is
possible to apply the centrifugal force toward the outer side in
the radial direction effectively to air in the back-surface gap
`g`, and reduce the pressure of the radially inner part of the
back-surface gap `g`. Accordingly, it is possible to suppress entry
of a leakage flow from the back-surface gap `g` to the bearing 10A,
and suppress inflow of the leakage flow into electric devices such
as the motor.
[0085] In some embodiments, as shown in FIG. 6, each of the ribs 44
has an airfoil shape. With the above configuration, it is possible
to form an airflow toward the outer side in the radial direction
effectively with the ribs 44 having an airfoil shape, in the
back-surface gap `g` upon rotation of the compressor impeller 4.
Accordingly, it is possible to suppress entry of a leakage flow
from the back-surface gap `g` to the bearing 10A, and suppress
inflow of the leakage flow into electric devices such as the motor
12.
[0086] In some embodiments, as depicted in FIG. 6 for instance,
each rib 44 is disposed so as to extend in a direction inclined
from the radial direction, such that the radially outer end 46 of
the rib 44 is positioned on the upstream side of the radially inner
end 48 of the rib 44, with respect to the rotational direction of
the compressor impeller 4.
[0087] With the above configuration, with the ribs 44 being
inclined in the above direction, it is possible to suppress inflow
of air into the gaps between the ribs 44 from the outer side in the
radial direction, during rotation of the compressor impeller 4.
Accordingly, it is possible to suppress entry of a leakage flow
from the back-surface gap `g` to the bearing 10A, and suppress
inflow of the leakage flow into electric devices such as the motor
12.
[0088] FIG. 7 is a schematic diagram showing a schematic
cross-sectional view in the vicinity of a back surface 16 of a
compressor impeller 4 of an electric supercharger 2 (2C) according
to an embodiment. FIG. 8 is a diagram showing a configuration
example of the rotary part 50 depicted in FIG. 7, showing an
example of the shape of the rotary part 50 in an axial-directional
view. FIG. 9 is a diagram showing a configuration example of the
rotary part 50 depicted in FIG. 7, showing an example of the shape
of the rotary part 50 in an axial-directional view. FIG. 10 is a
diagram showing a configuration example of the rotary part 50
depicted in FIG. 7, showing an example of the shape of the rotary
part 50 in an axial-directional view.
[0089] In some embodiments, as depicted in FIG. 7, the electric
supercharger further includes a rotary part 50 which protrudes
outward in the radial direction from the rotational shaft 6,
between the mechanical seal 20 and the back surface 16 of the
compressor impeller 4, and which is configured to rotate together
with the rotational shaft 6.
[0090] With the above configuration, a centrifugal force toward the
outer side in the radial direction is applied to air in the
back-surface gap `g` in accordance with rotation of the rotary part
50, and thereby it is possible to decrease the pressure of the
radially inner part of the back-surface gap `g`. Accordingly, it is
possible to suppress entry of a leakage flow from the back-surface
gap `g` to the bearing 10A, and suppress inflow of the leakage flow
into electric devices such as the motor 12. Further, by reducing
the pressure of the radially inner part of the back-surface gap
`g`, it is possible to decrease the spring force of the biasing
member 26 required to move the stationary ring 22 appropriately,
which makes it possible to suppress development of wear due to
friction between the stationary ring 22 and the rotary ring 24.
[0091] The shape of the rotary part 50 is not particularly limited.
For instance, the rotary part 51 may have an annular shape as
depicted in FIG. 8, or may have a plurality of protrusions 52 (four
protrusions 52 in the depicted embodiment) protruding outward in
the radial direction from the annular shape as depicted in FIGS. 9
and 10. The protrusions 52 may protrude in a radial fashion along
the radial direction as depicted in FIG. 9 for instance, or may
have a tapered shape protruding diagonally with respect to the
radial direction as depicted in FIG. 10.
[0092] FIG. 11 is a schematic diagram showing a schematic
cross-sectional view in the vicinity of a back surface 16 of a
compressor impeller 4 of an electric supercharger 2 (2D) according
to an embodiment. FIG. 12 is a graph showing the relationship
between the radial-directional position R and the gauge pressure P
of the back-surface gap `g`. The dotted line indicates an electric
supercharger 2 (2A) not including an abradable coating layer 90,
and the solid line indicates an electric supercharger 2 (2D)
including an abradable coating layer 90 formed on the facing
surface 21. FIG. 13 is a schematic diagram showing a schematic
cross-sectional view in the vicinity of a back surface 16 of a
compressor impeller 4 of an electric supercharger 2 (2E) according
to an embodiment.
[0093] In some embodiments, as depicted in FIG. 11, of the
back-surface side casing 14, an abradable coating layer 90 is
formed on at least a part of the facing surface 21 facing the back
surface 16 of the compressor impeller 4 (the entire facing surface
21 in the depicted embodiment).
[0094] With the above configuration, the abradable coating layer 90
would be ground upon rotation of the compressor impeller 4 even if
the abradable coating layer 90 formed on the facing surface 21
makes contact with the back surface 16 of the compressor impeller
4. Thus, it is possible to reduce the clearance C between the back
surface 16 and the back-surface side casing 14 (distance between
the back surface 16 and the back-surface side casing 14).
Accordingly, it is possible to promote a pressure decrease toward
the inner side in the radial direction, in the back-surface gap
`g`, as described below.
[0095] FIG. 12 is a graph schematically showing the relationship
between the radial-directional position R and the gauge pressure P
of the back-surface gap `g`. The dotted line indicates an electric
supercharger 2 (2A) not including an abradable coating layer 90,
and the solid line indicates an electric supercharger 2 (2D)
including an abradable coating layer 90 formed on the facing
surface 21. Herein, the clearance C between the back surface 16 and
the back-surface side casing 14 of the electric supercharger 2 (2D)
is set to be smaller than the clearance between the back surface 16
and the back-surface side casing 14 of the electric supercharger 2
(2A).
[0096] As depicted in FIG. 12, in both of the electric supercharger
2 (2A) and the electric supercharger 2 (2D), the pressure decreases
in the back-surface gap g, toward the inner side in the radial
direction. Particularly in a region where the radial-directional
position R is small, the pressure in the back-surface gap `g` in
the electric supercharger 2(2D) is reduced considerably compared to
that in the electric supercharger 2 (2A).
[0097] Accordingly, with the electric supercharger 2, by promoting
the pressure decrease toward the inner side in the radial direction
in the back-surface gap `g`, it is possible to reduce the
axial-directional pressure difference between the pressure of the
radially inner part (pressure near the mechanical seal 20) of the
back-surface gap `g` and the pressure near the bearing 10A and thus
it is possible to suppress entry of a leakage flow toward the
bearing 10A (toward the mechanical seal 20) from the back-surface
gap `g`. Accordingly, it is possible to suppress inflow of the
leakage flow into electric devices such as the motor 12 and an
inverter (not depicted). Thus, it is possible to suppress
occurrence of malfunction or the like of the electric devices, and
operate the electric supercharger 2 stably.
[0098] Further, the compressor impeller 4 receives a thrust force
toward the upstream in the intake direction of air (left side in
the drawing), in the axial direction, when air is compressed. In
the above electric supercharger 2, it is possible to reduce the
pressure in the back-surface gap `g` for the compressor impeller 4,
and thus it is possible to reduce the thrust force in the axial
direction.
[0099] Further, by promoting the pressure decrease toward the inner
side in the radial direction in the back-surface gap `g` to reduce
the pressure of the radially inner part of the back-surface gap
`g`, it is possible to decrease the spring force of the biasing
member 26 required to move the stationary ring 22 appropriately,
which makes it possible to suppress development of wear due to
friction between the stationary ring 22 and the rotary ring 24.
[0100] In an embodiment, in FIG. 11, the ratio C/Ri of the
clearance C between the back surface 16 of the compressor impeller
4 and the back-surface side casing 14 to the outer diameter Ri of
the compressor impeller 4 is less than 0.5%.
[0101] With the above configuration, it is possible to promote a
pressure decrease toward the inner side in the radial direction, in
the back-surface gap `g`, effectively. According to the inventors
of the present invention, when comparing a case where the abradable
coating layer 90 is provided and the ratio C/Ri is set to be 0.8%
and a case where the abradable coating layer 90 is not provided and
C/Ri is set to be 0.25%, the former can reduce more pressure of the
radially inner part of the back-surface gap `g` by 26% compared to
the latter.
[0102] In an embodiment, as depicted in FIG. 13, the abradable
coating layer 90 is formed on at least a part of the back surface
16 of the compressor impeller 4. Furthermore, the ratio C/Ri of the
clearance C between the back surface 16 of the compressor impeller
4 and the back-surface side casing 14 to the outer diameter Ri of
the compressor impeller 4 is less than 0.5%.
[0103] With the above configuration, the abradable coating layer 90
would be ground upon rotation of the compressor impeller 4 even if
the abradable coating layer 90 formed on the back surface 16 of the
compressor impeller 4 makes contact with the facing surface 21 of
the back-surface side casing 14. Thus, it is possible to reduce the
clearance C between the back surface 16 and the back-surface side
casing 14. Accordingly, it is possible to promote a pressure
decrease toward the inner side in the radial direction, in the
back-surface gap `g`.
[0104] Thus, it is possible to reduce the axial-directional
pressure difference between the pressure of the radially inner part
of the back-surface gap `g` (pressure near the mechanical seal 20)
and the pressure near the bearing 10A, and thus it is possible to
suppress entry of a leakage flow toward the bearing 10A (toward the
mechanical seal 20) from the back-surface gap `g`. Accordingly, it
is possible to suppress inflow of the leakage flow into electric
devices such as the motor 12 and an inverter (not depicted). Thus,
it is possible to suppress occurrence of malfunction or the like of
the electric devices, and operate the electric supercharger
stably.
[0105] Further, it is possible to reduce the pressure of the
back-surface gap `g` by reducing the clearance C, and thus it is
possible to reduce the thrust force in the axial direction in the
compressor impeller 4.
[0106] Further, by promoting the pressure decrease toward the inner
side in the radial direction in the back-surface gap `g` to reduce
the pressure of the radially inner part of the back-surface gap
`g`, it is possible to decrease the spring force of the biasing
member 26 required to move the stationary ring 22 appropriately,
which makes it possible to suppress development of wear due to
friction between the stationary ring 22 and the rotary ring 24.
[0107] In some embodiments, as depicted in FIGS. 14 and 15 for
instance, the electric supercharger 2 (2A to 2E) further includes a
communication hole 53 serving as an internal-pressure adjustment
mechanism, configured to adjust the pressure inside the
back-surface side casing 14 by bringing the inside and the outside
of the back-surface side casing 14 into communication. The
communication hole 53 may be disposed on the compressor side of the
back-surface side casing 14 as depicted in FIG. 14, or on the
inverter side as depicted in FIG. 15, or on both sides. The
position, shape, and dimension like hole diameter of the
communication hole 53 are to be designed to be optimum in
accordance with the size of the electric supercharger 2. Further,
in the embodiment depicted in FIGS. 14 and 15, on the outer end
portion side of the communication hole 53, a waterproof ventilation
filter 55 is disposed, which protects the inside of the
back-surface side casing 14 from dust, water, oil, and the like
while adjusting the pressure and the temperature inside the
back-surface side casing 14.
[0108] With the above configuration, even in a case where the
pressure of the radially inner part of the back-surface gap `g` is
low, it is possible to stabilize the pressure balance across the
mechanical seal 20 by adjusting the pressure inside and outside the
back-surface side casing 14 through the communication hole 53.
Accordingly, it is possible to suppress entry of a leakage flow to
the bearings 10A, 10B through the back-surface gap `g` stably with
the mechanical seal 20.
[0109] FIG. 16 is a schematic configuration diagram of an engine
device 100 to which the above described electric supercharger 2 (2A
to 2E) can be applied preferably. FIG. 16 is a diagram of an
embodiment of an engine device 100 in a case where the electric
supercharger 2 is used as a high-pressure stage supercharger of a
two-stage supercharging system.
[0110] The engine device 100 depicted in FIG. 16 includes, as
depicted in the drawing, an engine 54, an intake passage 56 through
which intake gas to be supplied to the engine 54 flows, an exhaust
passage 58 through which exhaust gas discharged from the engine 54
flows, a turbocharger 60, and the above described electric
supercharger 2.
[0111] The turbocharger 60 includes an exhaust turbine 64 disposed
in the exhaust passage 58, a compressor 62 disposed in the intake
passage 56, and an exhaust turbine shaft 63 coupling the exhaust
turbine 64 and the compressor 62. The turbocharger 60 is configured
such that the exhaust turbine 64 is driven by exhaust gas
discharged from the engine 54, and thereby the compressor 62 is
coaxially driven via the turbine shaft 63, so as to supercharge
intake gas flowing through the intake passage 56.
[0112] The electric supercharger 2 is disposed on the downstream
side of the compressor 62 in the intake passage 56, and intake gas
compressed by the compressor 62 of the turbocharger 60 is supplied
to the compressor impeller 4 of the electric supercharger 2. As
described above, the engine device 100 of the present embodiment is
configured as a two-stage supercharging system in which the
turbocharger 60 is provided as a low-pressure stage supercharger
and the electric supercharger 2 is provided as a high-pressure
stage supercharger.
[0113] A bypass intake passage 66 bypassing the electric
supercharger 2 is connected to the intake passage 56. A bypass
valve 68 is disposed in the bypass intake passage 66. Further, by
adjusting the valve opening degree of the bypass valve 68, the flow
rate of intake gas flowing into the electric supercharger 2 is
controlled.
[0114] Further, on the downstream side of the electric supercharger
2 in the intake passage 56, an intermediate cooler 70 for cooling
intake gas to be supplied to the engine 54 is disposed.
[0115] Furthermore, the engine device 100 includes an EGR passage
72 that connects the downstream side of the exhaust turbine 64 in
the exhaust passage 58 and the upstream side of the compressor 62
in the intake passage 56. An EGR valve 74 is disposed in the EGR
passage 72. Further, by adjusting the valve opening degree of the
EGR valve 74, exhaust gas having a flow rate corresponding to the
valve opening degree returns to the intake passage 56. Further,
intake gas containing the recirculated exhaust gas is supplied to
the compressor impeller 4 of the electric supercharger 2.
[0116] In the above engine device 100, the bypass valve 68 is
closed when the engine rotates at a low speed. The intake gas
pressurized by the turbocharger 60 serving as a low-pressure stage
supercharger is supplied to the electric supercharger 2 serving as
a high-pressure stage supercharger as indicated by the arrow `a`,
to be pressurized further. Thus, compared to a case where the
electric supercharger 2 is disposed at the low-pressure stage, the
differential pressure between the radially outer part and the
radially inner part of the compressor in the electric supercharger
2 becomes high, and high-temperature and high-pressure intake air
enters the above described back-surface gap `g`.
[0117] Furthermore, in the engine device 100, the bypass valve 68
is open and the electric supercharger 2 is stopped when the engine
rotates at a high speed. In this case, the intake gas pressurized
by the turbocharger 60 serving as a low-pressure stage supercharger
is supplied to the downstream side of the electric supercharger 2
through the bypass intake passage 66, as indicated by the arrow
`b`. Thus, the boost pressure of the turbocharger 60 creates a
differential pressure between the radially outer part and the
radially inner part of the compressor in the electric supercharger
2, and causes intake air to enter the above described back-surface
gap `g`.
[0118] In this regard, by applying the above described electric
supercharger 2 (2A to 2E) to the engine device 100, it is possible
to suppress entry of high-temperature and high-pressure intake air
to the bearing side via the back-surface gap `g`, and thus it is
possible to suppress occurrence of troubles in devices such as the
bearings 10A, 10B and the motor 12, effectively.
[0119] Furthermore, normally, in a case where a part of exhaust gas
is recirculated to the upstream side of the low-pressure stage
supercharger by a two-stage supercharging system including the
above described EGR passage, and a case where an intermediate
cooler is used, and a case where blow-by gas is returned to the
inlet of the electric supercharger, for instance, air containing
condensed water is taken in from the inlet of the electric
supercharger, and thus a leakage flow passing through the
back-surface gap and entering the bearing side is likely to cause
trouble in operation of devices such as the motor and the
inverter.
[0120] In this regard, by applying the above described electric
supercharger 2 (2A to 2E) to the engine device 100, it is possible
to suppress entry of high-temperature and high-pressure intake air
to the bearing side via the back-surface gap `g`, and thus it is
possible to suppress occurrence of troubles in devices such as the
bearings 10A, 10B and the motor 12, effectively.
[0121] Embodiments of the present invention were described in
detail above, but the present invention is not limited thereto, and
various amendments and modifications may be implemented.
[0122] For instance, in the above described embodiments, the
back-surface side casing 14 surrounds the mechanical seal 20, the
bearings 10A, 10B, and the motor 12. Nevertheless, the
configuration of the back-surface side casing 14 is not limited to
this. For instance, the back-surface side casing 14 may surround
only the mechanical seal 20, and a casing other than the
back-surface side casing 14 may surround the bearings 10A, 10B and
the motor 12. Alternatively, the back-surface side casing 14 may
surround only the mechanical seal 20 and the bearing 10A, and a
casing other than the back-surface side casing 14 may surround the
bearing 10B and the motor 12.
[0123] Furthermore, while the above described electric supercharger
2 (2A to 2E) includes the mechanical seal 20, the electric
supercharger 2 may not necessarily include the mechanical seal 20
in another embodiment.
[0124] FIG. 17 is a schematic diagram showing a schematic
cross-sectional view in the vicinity of a back surface 16 of a
compressor impeller 4 of an electric supercharger 2 (2F) according
to another embodiment. FIG. 18 is a schematic diagram showing a
schematic cross-sectional view in the vicinity of a back surface 16
of a compressor impeller 4 of an electric supercharger 2 (2G)
according to another embodiment. FIG. 19 is a schematic diagram
showing a schematic cross-sectional view in the vicinity of a back
surface 16 of a compressor impeller 4 of an electric supercharger 2
(2H) according to another embodiment. FIG. 20 is a schematic
diagram showing a schematic cross-sectional view in the vicinity of
a back surface 16 of a compressor impeller 4 of an electric
supercharger 2 (2I) according to another embodiment. FIG. 21 is a
schematic diagram showing a schematic cross-sectional view in the
vicinity of a back surface 16 of a compressor impeller 4 of an
electric supercharger 2 (2J) according to another embodiment. FIG.
22 is a schematic diagram showing a schematic cross-sectional view
in the vicinity of a back surface 16 of a compressor impeller 4 of
an electric supercharger 2 (2K) according to another
embodiment.
[0125] The basic configuration of the electric supercharger 2 (2F
to 2K) is similar to that of the electric supercharger 2 depicted
in FIG. 1, except that the mechanical seal 20 is not provided.
Thus, the same configurations are associated with the same
reference numerals to omit description, and the characteristic
configurations of the respective modified examples will be mainly
described.
[0126] In some embodiments depicted in FIGS. 17 to 19, the electric
supercharger 2 (2F to 2H) further includes a rotary part 76 which
protrudes outward in the radial direction from the rotational shaft
6, between the back-surface side casing 14 and the back surface 16
of the compressor impeller 4, and which is configured to rotate
together with the rotational shaft 6. Further, the radially outer
end 78 of the rotary part 76 is positioned on the outer side of the
radially inner end 80 of the back-surface side casing 14 in the
radial direction.
[0127] Although the shape of the rotary part 76 is not particularly
limited, the respective shapes of the rotary part 50 described with
reference to FIGS. 8 to 10 may be applied. Furthermore, the rotary
part 76 may be disposed at a distance from the back surface 16 of
the compressor impeller 4 as depicted in FIG. 17, or in contact
with the back surface 16 of the compressor impeller 4 as depicted
in FIGS. 18 and 19, or integrally with the compressor impeller 4 or
a non-depicted sleeve engaged with the rotational shaft 6. Further,
as depicted in FIGS. 18 and 19, the rotary part 76 may protrude
toward the back surface 16 past the facing surface 21 of the
back-surface side casing 14 that faces the back surface 16.
Furthermore, in a case where a recessed portion 82 is formed on the
back surface 16 of the compressor impeller 4, the rotary part 76
may include a protruding portion 84 protruding in the axial
direction so as to enter the inside of the recessed portion 82 as
depicted in FIG. 19.
[0128] In the embodiment depicted in FIG. 20, the electric
supercharger 2 (2I) includes a seal unit 9 instead of the
mechanical seal 20 of the electric supercharger 2 (2B) depicted in
FIG. 4. In the electric supercharger 2 (2I), similarly to the
electric supercharger 2 (2B), a plurality of ribs 44 are disposed
at intervals in the circumferential direction, on the back surface
16 of the compressor 4.
[0129] Furthermore, the seal unit 9 includes a sleeve 86 and at
least one piston ring 88 (in the depicted embodiment, two piston
rings 88). The sleeve 86 is disposed such that an end side of the
sleeve 86 is in contact with the back surface 16 of the compressor
impeller 4, in a state where the sleeve 86 is engaged with the
rotational shaft 6. The piston ring 88 is engaged with an annular
groove disposed on the outer peripheral surface of the sleeve 86
and is in contact with the back-surface side casing 14, thereby
sealing the gap between the rotational shaft 6 and the back-surface
side casing 14.
[0130] Also with the above configuration, by providing the
plurality of ribs 44, a centrifugal force toward the outer side in
the radial direction is applied to air in the back-surface gap `g`
upon rotation of the compressor impeller 4, and thereby it is
possible to decrease the pressure of the radially inner part of the
back-surface gap `g`. Accordingly, it is possible to suppress entry
of a leakage flow from the back-surface gap `g` to the bearing 10A,
and suppress inflow of the leakage flow into electric devices such
as the motor.
[0131] In the embodiment depicted in FIG. 21, the electric
supercharger 2 (2J) includes a seal unit 9 instead of the
mechanical seal 20 of the electric supercharger 2 (2D) depicted in
FIG. 11. In the electric supercharger 2 (2J), similarly to the
electric supercharger 2 (2D), of the back-surface side casing 14,
an abradable coating layer 90 is formed on at least a part of the
facing surface 21 facing the back surface 16 of the compressor
impeller 4 (the entire facing surface 21 in the depicted
embodiment).
[0132] Also with the above configuration, by promoting the pressure
decrease toward the inner side in the radial direction in the
back-surface gap `g`, it is possible to reduce the
axial-directional pressure difference between the pressure of the
radially inner part of the back-surface gap `g` (pressure near the
seal unit 9) and the pressure near the bearing 10A and thus it is
possible to suppress entry of a leakage flow toward the bearing 10A
(toward the seal unit 9) from the back-surface gap `g`.
Accordingly, it is possible to suppress inflow of the leakage flow
into electric devices such as the motor 12 and an inverter (not
depicted). Thus, it is possible to suppress occurrence of
malfunction or the like of the electric devices, and operate the
electric supercharger 2 stably.
[0133] Further, the compressor impeller 4 receives a thrust force
toward the upstream in the intake direction of air (left side in
the drawing), in the axial direction, when air is compressed. In
the above electric supercharger 2 (2J), it is possible to reduce
the pressure in the back-surface gap `g` for the compressor
impeller 4, and thus it is possible to reduce the thrust force in
the axial direction.
[0134] In the embodiment depicted in FIG. 22, the electric
supercharger 2 (2K) includes a seal unit 9 instead of the
mechanical seal 20 of the electric supercharger 2 (2E) depicted in
FIG. 13. In the electric supercharger 2 (2K), similarly to the
electric supercharger 2 (2E), the abradable coating layer 90 is
formed on at least a part of the back surface 16 of the compressor
impeller 4.
[0135] Also with the above configuration, by promoting the pressure
decrease toward the inner side in the radial direction in the
back-surface gap `g`, it is possible to reduce the
axial-directional pressure difference between the pressure of the
radially inner part of the back-surface gap `g` (pressure near the
seal unit 9) and the pressure near the bearing 10A and thus it is
possible to suppress entry of a leakage flow toward the bearing 10A
(toward the seal unit 9) from the back-surface gap `g`.
[0136] Further, the compressor impeller 4 receives a thrust force
toward the upstream in the intake direction of air (left side in
the drawing), in the axial direction, when air is compressed. In
the above electric supercharger 2 (2K), it is possible to reduce
the pressure in the back-surface gap `g` for the compressor
impeller 4, and thus it is possible to reduce the thrust force in
the axial direction.
[0137] Further, while the electric supercharger 2 (2A to 2E) is
described as preferably applicable as a high-pressure stage
supercharger of a two-stage supercharging system in the embodiment
depicted in FIG. 16, the electric supercharger 2 (2A to 2K) may be
used as a low-pressure stage supercharger of a two-stage
supercharging system as depicted in FIG. 23.
[0138] Hereinafter, the engine device 110 depicted in FIG. 23 will
be described. Of the configuration depicted in FIG. 23, the
configurations similar to those depicted in FIG. 16 is associated
with the same reference numerals to omit description, and what is
different from the configuration depicted in FIG. 16 will be mainly
described.
[0139] In the engine device 100 depicted in FIG. 23, the electric
supercharger 2 is disposed on the upstream side of the compressor
62 in the intake passage 56, and intake gas compressed by the
electric supercharger 2 is supplied to the compressor 62 of the
turbocharger 60. As described above, the engine device 110 is
configured as a two-stage supercharging system in which the
turbocharger 60 is provided as a high-pressure stage supercharger
and the electric supercharger 2 is provided as a low-pressure stage
supercharger.
[0140] A bypass intake passage 66 bypassing the electric
supercharger 2 is connected to the intake passage 56. A bypass
valve 68 is disposed in the bypass intake passage 66. Further, by
adjusting the valve opening degree of the bypass valve 68, the flow
rate of intake gas flowing into the electric supercharger 2 is
controlled.
[0141] Further, on the downstream side of the compressor 62 in the
intake passage 56, an intermediate cooler 70 for cooling intake gas
to be supplied to the engine 54 is disposed.
[0142] Furthermore, the engine device 110 includes an EGR passage
72 that connects the downstream side of the exhaust turbine 64 in
the exhaust passage 58 and the upstream side of the electric
supercharger 2 in the intake passage 56. An EGR valve 74 is
disposed in the EGR passage 72. Further, by adjusting the valve
opening degree of the EGR valve 74, exhaust gas having a flow rate
corresponding to the valve opening degree returns to the intake
passage 56. Further, intake gas containing the recirculated exhaust
gas is supplied to the compressor impeller 4 of the electric
supercharger 2.
[0143] In the above engine device 110, the bypass valve 68 is
closed when the engine rotates at a low speed. The intake gas
pressurized by the electric supercharger 2 serving as a
low-pressure stage supercharger is supplied to the compressor 62 of
the turbocharger 60 serving as a high-pressure stage supercharger
as indicated by the arrow `c`, to be pressurized further. Thus, the
boost pressure of the electric supercharger 2 is applied to the gap
between the radially outer part and the radially inner part of the
compressor in the electric supercharger 2, and causes intake air to
enter the above described back-surface gap `g`.
[0144] Furthermore, in the engine device 110, the bypass valve 68
is open and the electric supercharger 2 is stopped when the engine
rotates at a high speed. In this case, as indicated by the arrow
`d`, intake gas is supplied to the compressor 62 through the bypass
intake passage 66, and thus substantially no intake air enters the
back-surface gap `g` of the electric supercharger 2.
[0145] As described above, by applying the above described electric
supercharger 2 (2A to 2K) to the engine device 110, it is possible
to suppress entry of high-temperature and high-pressure intake air
to the bearing side via the back-surface gap `g`, and thus it is
possible to suppress occurrence of troubles in devices such as the
bearings 10A, 10B and the motor 12, effectively.
REFERENCE SIGNS LIST
[0146] 2 (2A to 2K) Supercharger [0147] 4 Compressor impeller
[0148] 6 Rotational shaft [0149] 8 Impeller casing [0150] 9 Seal
unit [0151] 10A, 10B Bearing [0152] 12 Motor [0153] 14 Back-surface
side casing [0154] 16 Back surface [0155] 18 Inverter housing
portion [0156] 20 Mechanical seal [0157] 21, 32 Facing surface
[0158] 22 Stationary ring [0159] 24 Rotary ring [0160] 26 Biasing
member [0161] 28, 30 Surface [0162] 34 Groove [0163] 36, 38 Space
[0164] 40, 48, 80 Radially inner end [0165] 42, 46, 78 Radially
outer end [0166] 44 Rib [0167] 50, 76 Rotary part [0168] 52
Protrusion [0169] 53 Communication hole [0170] 54 Engine [0171] 55
Waterproof ventilation filter [0172] 56 Intake passage [0173] 58
Exhaust passage [0174] 60 Turbocharger [0175] 62 Compressor [0176]
63 Turbine shaft [0177] 64 Exhaust turbine [0178] 66 Bypass intake
passage [0179] 68 Bypass valve [0180] 70 Intermediate cooler [0181]
72 Passage [0182] 74 Valve [0183] 82 Recessed portion [0184] 84
Protruding portion [0185] 86 Sleeve [0186] 88 Piston ring [0187] 90
Abradable coating layer [0188] 100, 110 Engine device
* * * * *