Pumps – Motor driven – Electric or magnetic motor
Reexamination Certificate
2000-06-14
2001-05-08
Walberg, Teresa (Department: 3742)
Pumps
Motor driven
Electric or magnetic motor
C415S055100
Reexamination Certificate
active
06227819
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to a fuel pumping assembly for drawing fuel from a reservoir and supplying that fuel to an engine.
BACKGROUND OF THE INVENTION
It is known for a fuel pumping assembly to include an electric motor and a fuel pump module supported together in a housing. The fuel pump module in such an assembly will generally include a module housing, an impeller that is driven by the electric motor and rotates within an impeller cavity formed in the module housing, and a semi-circular pumping channel including upper and lower pumping channel portions formed around a circular periphery of the impeller cavity. The impeller may include axially upper and lower impeller vanes spaced around an outer circumferential periphery of the impeller that move fluid through the upper and lower portions of the pumping channel, respectively, as the impeller rotates within the impeller cavity. The module housing will also include an inlet port and an exhaust port that may extend axially through respective lower and upper walls of the module housing and connect with respective inlet and outlet ends of the pumping channel. To improve pump efficiency and reduce power requirements, it is desirable to shape the pumping channel and the exhaust port to minimize fluid losses.
For example, European Patent Application EPO 784 158 AZ discloses an electric motor regenerative turbine fuel pump assembly that improves efficiency by shaping the exhaust port of its pump module to include an arcuate trench in an upper wall of its module housing. As shown in
FIGS. 1-7
, the pump module
20
has an exhaust port
22
located along a portion of a circumferential sidewall
24
of a module housing
26
of the module
20
adjacent an exit end
28
of its pumping channel
30
in which an impeller
31
is received. The exhaust port
22
also includes an opening
32
that leads from the outlet end
28
of the pumping channel
30
into the trench
33
. The trench
33
is defined by a generally vertical trench end wall
34
disposed upstream from a ramp
36
that inclines from a floor
38
of the trench
33
, in a downstream direction, i.e., the direction of impeller rotation, to an upper surface
40
of the module housing
26
. The trench
33
is further defined by an arcuate radially inner wall
42
that stands opposite and parallel to an arcuate radially outer wall
44
. A thin circumferential band of material
46
surrounds the module housing
26
and defines the outer wall
44
of the trench
33
. However, the exhaust port opening
32
is disposed radially outward from the impeller
31
and the exit end
28
of the pumping channel
30
. As best shown in
FIGS. 6 and 7
, this requires fuel exiting upper and lower portions
45
,
47
of the pumping channel
30
to impact respective upper and lower channel exit end walls
48
,
49
of the upper and lower portions
45
,
47
of the pumping channel
30
before turning radially outward to exit through the exhaust port opening
32
resulting in fluid losses. In other words, the exit end
28
of the pumping channel
30
forms an elbow redirecting fluid flow radially outward from the channel
30
and through the exhaust port opening
32
.
The exhaust port opening
32
includes a generally rectangular horizontal portion
54
defined on three sides by the trench end wall
34
, the outer wall
44
and a leading or upstream edge
56
of the ramp
36
. A fourth side of the horizontal portion
54
of the exhaust port opening
32
is defined by an imaginary line extending through space between respective radially inner ends of the sides defined by the trench end wall
34
and the upstream edge
56
of the ramp
36
. The exhaust port opening
32
also includes a generally rectangular vertical portion
58
formed into the inner wall
42
. The vertical portion
58
of the exhaust port opening
32
is positioned to allow fuel to exit directly from the upper portion
45
of the pumping channel
30
into the exhaust port trench
33
. The horizontal portion
54
of the exhaust port opening
32
is formed in the floor
38
of the trench
33
to allow fuel to exit vertically upward from the lower portion
47
of the exit end
28
of the pumping channel
30
and into the trench
33
. However, fuel exiting vertically through the horizontal portion
54
of the exhaust port opening
32
necessarily impinges on fuel exiting laterally from the vertical portion
58
of the exhaust port opening
32
resulting in impingement mixing at the opening and associated turbulence and fluid losses.
As best shown in
FIG. 6
, the exhaust port trench
33
is shaped to discharge the mixed upper and lower fuel flows up the ramp
36
and generally vertically away from the pumping module
20
into a chamber
60
of the fuel pump housing
62
that contains the electric motor. The fuel continues past the motor and out an outlet of the pump housing to supply fuel under pressure to an operating engine. The fuel pumping assembly of the Denso pump includes an electric motor (not shown) connected to and constructed to rotate the impeller.
SUMMARY OF THE INVENTION
The invention is a fuel pumping assembly that includes a fuel pump module supported in a fuel pump housing. The fuel pump module includes an impeller rotatably supported within an impeller cavity formed in a pump module housing, and a generally semi-circular pumping channel formed in the housing around a generally circular periphery of the impeller cavity. The impeller includes axially upper and lower impeller vanes spaced around an outer circumferential periphery of the impeller that are configured and positioned to move fluid through the pumping channel as the impeller rotates within the impeller cavity. The module housing includes inlet and exhaust ports communicating with respective inlet and exit passages of the pumping channel.
The exit passage of the pumping channel extends generally tangentially outward through the sidewall of the module housing. This aligns the exhaust port with the tangential flow of fuel from the exit passage of the pumping channel such that fuel exits the pumping channel relatively unimpeded and flows smoothly into the trench. Therefore, a fuel pumping assembly constructed according to the invention is able to pump fuel more efficiently.
Preferably, the cross-sectional area of the exit passage of the pumping channel gradually increases toward the exhaust port which further reduces back pressure on the impeller and increases efficiency. The exit passage of the pumping channel and the exhaust port opening are constructed to allow a lower fuel stream exiting the lower portion of the pumping channel to remain parallel to and below an upper fuel stream exiting the upper portion of the pumping channel while flowing into the exhaust port trench which reduces fluid losses by avoiding impingement mixing. The exhaust port opening and trench are constructed to allow lower and upper fuel streams from the lower and upper portions of the pumping channel, respectively, to both exit laterally into the exhaust port trench which prevents uneven back pressure on the impeller upper and lower vanes and unbalanced impeller loads that would otherwise result in reduced efficiency or even spin welding of the impeller to the impeller chamber. Preferably, the pump housing surrounding the fuel pump module defines a radially outer wall of the exhaust port trench precluding the need to form such a wall while molding the module housing. The trench may include a ramp that smoothly redirects exiting fuel axially upward from the pumping module, again improving efficiency and reducing power requirements.
Objects, features and advantages of this invention include a turbine pump that has significantly improved efficiency, may be readily incorporated into existing fuel pump designs, has significantly improved balancing and decreases axial loads on the impeller particularly during high flow rate operating conditions, and is of relatively simple design and economical manufacture and assembly and in service has a significantly increased useful li
Gettel Bryan J.
Moss Glenn A.
Ross Joseph M.
Fastovsky Leonid
Reising Ethington, Barnes, Kisselle, Learman & McCulloch, P.C.
Walberg Teresa
Walbro Corporation
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