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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a fuel feed pump, and more particularly to a fuel
feed pump of a frictional pump type, e.g. one effectively used for an
electronically controlled fuel injection device.
2. Related Art Statement
Since a frictional pump used in a fuel feed pump has no self-priming
properties in general, as the vapor quantity in a casing increases,
discharge quantity decreases, thus resulting in a vapor lock.
Therefore, it has been the common practice that, in the conventional fuel
feed pump of this type, deairing holes are opened in a generally annular
groove path formed in an annular zone between an intake port and a
discharge port except a liquid sealing portion in a casing, whereby vapor
is deaired through the deairing holes when the fuel is separated from the
vapor by the centrifugal force.
The reason why the deairing holes have heretofore been downwardly opened
resides in that, in order to wash and cool a commutator and brushes in a
motor portion provided in the upper portion of the fuel feed pump, the
interior of a housing of the motor portion is made to serve as a fuel
path, whereby the interior of the housing of the motor portion is highly
pressurized, therefore the vapor cannot be deaired through the deairing
holes, so that the deairing holes are opened downwardly in order that the
vapor does not intrude into the interior of the housing where the motor
portion is disposed.
However, recently, the number of component parts housed in an engine spaces
of a motor vehicle has greatly increased, whereby, with the fuel feed pump
in which only the downwardly opened deairing holes are formed in the
intermediate portion of the groove path, the deairing effect has become
insufficient.
Namely, as the number of the component parts in the engine space of the
motor vehicle is increased highly, the temperature in the engine space
tends to be raised. In an electronically controlled fuel injection device,
a part of the fuel constantly circulates through the engine space and
returns to a fuel tank, whereby the temperature of the fuel in the tank
tends to further easily increase. As the temperature of the fuel is
raised, boiling of the fuel itself and agitation of the fuel by the fuel
feed pump produce a large quantity of vapor. When the large quantity of
vapor is produced, the arrangement in which only the deairing holes are
opened in the intermediate portion of the groove path can not deair the
vapor sufficiently. Particularly, the vapor is lower in gravity than the
fuel, whereby the vapor tends to accumulate in the upper space of the
groove path, so that, in the conventional fuel feed pump in which the
deairing holes are opened downwardly, the vapor cannot be deaired
sufficiently.
Then, even if it is tried to deair the vapor into the interior of the motor
portion from the upper space of the groove path, the vapor cannot be
discharged upwardly because the vapor discharged from the deairing holes
is lower in pressure than the highly pressurized fuel passing through the
interior of the motor portion.
Further, when the highly pressurized fuel and the vapor which has not been
deaired return to the intake side, the pressure is abruptly lowered,
whereby intake of the fuel through the intake port is disturbed by the new
production of the vapor and the expansion of the vapor, so that the vapor
lock tends to occur.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a fuel feed pump, wherein
the quantity of vapor produced in the vicinity of an intake port is
reduced, and, even when the large quantity of vapor is produced, vapor can
be deaired sufficiently.
Another object of the present invention is to provide a fuel feed pump
wherein vapor produced in the upper portion of a groove path is discharged
to the outside of a casing, and returns of the remaining vapor which has
not been deaired through deairing holes and a part of the highly
pressurized fuel are discharged through an exhaust hole formed in a
sealing portion so as to suppress the production of vapor itself and to
sufficiently deair vapor even when the large quantity of vapor is
produced.
The fuel feed pump according to the present invention is characterized in
that, in a fuel feed pump comprising: a casing immersed in a fuel tank for
a motor vehicle; an impeller rotatably installed in the casing and
provided on the outer periphery thereof with a plurality of grooves; a
liquid sealing portion formed in a position close to the impeller on
rotating loci of a group of the grooves of the impeler in the casing; an
intake port and a discharge port respectively opened in positions
interposing the liquid sealing portion in the circumferential direction in
the casing; and a generally annular groove path formed between the intake
port and the discharge port in a zone excluding the liquid sealing portion
of the casing; an exhaust port is opened in the intermediate portion of
the liquid sealing portion in a manner to be communicated with an inner
space of this liquid sealing portion and this exhaust port is communicated
with the outside of the casing.
Furthermore, the groove path is formed with deairing holes for
communicating the interior of the groove path with the outside of a
housing.
In the fuel feed pump according to the present invention, the exhaust port
is opened in the liquid sealing portion, whereby the fuel is reduced in
pressure here, so that new production of the vapor can be suppressed.
Furthermore, the remaining vapor which has not been discharged through the
deairing holes can be deaired through this exhaust port. Accordingly, the
quantity of the vapor produced in the vicinity of the intake port is
decreased, so that a vapor lock can be avoided.
Furthermore, another fuel feed pump according to the invention is
characterized in that the deairing holes are opened in the casing in a
manner to communicate the liquid sealing portion with the outside of the
casing, and a deairing groove is formed at least in the upper end surface
of this casing in such a manner that one end thereof is communicated with
the upper space of the groove path and the other end thereof is
communicated with the deairing holes, passing through the liquid sealing
portion.
In the above-described fuel feed pump of another type according to the
present invention, the deairing groove is communicated with the upper
space of the groove path, so that the vapor which tends to accumulate in
the upper space of the groove path can be very effectively deaired from
the groove path by this deairing groove. Accordingly, the quantity of the
vapor reaching the vicinity of the intake port is decreased and the intake
port is constantly filled up with the fuel, so that the vapor lock can be
avoided.
Furthermore, the deairing groove traverses the liquid sealing portion,
whereby the pressure in the liquid sealing portion is reduced, so that the
occurrence of a vapor lock can be further prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects and features of the present invention will
become more apparent when referred to the following descriptions given in
conjunction with the accompanying drawings, wherein like reference
numerals denote like elements, and in which:
FIG. 1 is a partially omitted plan sectional view taken along the line I--I
in FIG. 3 showing an embodiment of the fuel feed pump according to the
present invention;
FIG. 2 is an enlarged partially sectional view taken along the line II--II
in FIG. 1;
FIG. 3 is a front sectional view showing an embodiment of the fuel feed
pump according to the present invention;
FIG. 4 is a comparative graphic chart for explaining the actions;
FIG. 5 is a partially omitted plan sectional view showing another
embodiment of the fuel feed pump according to the invention, taken along
the line V--V in FIG. 7;
FIG. 6 is an enlarged partially sectional view taken along the line VI--VI
in FIG. 5;
FIG. 7 is a front sectional view showing the fuel feed pump thereof;
FIG. 8 is an enlarged partially sectional view showing a further embodiment
of the present invention, corresponding to FIG. 7; and
FIG. 9 is a comparative graphic chart explaining the actions.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiment 1
Referring to the drawings, in this Embodiment 1 shown in FIG. 1 through 4,
a fuel feed pump according to the present invention 10 has a pump portion
12 and a motor portion 30, both portions being installed in a housing 11.
This fuel feed pump 10 is wholely immersed in a fuel tank, not shown, with
the pump portion disposed below. A casing 13 of the pump portion 12 is
fixedly incorporated in the bottom end portion of the housing 11. The
casing 13 has a pump plate 14 and a pump head 15, both of which are
assembled into the housing 11 with the both members disposed back to back.
A generally disk-shaped hollow pump chamber 16 is defined by surfaces of
the pump plate 14 and the pump head 15 which face each other. The pump
chamber 16 incorporates therein a disk-shaped impeller 17 rotatably and
coaxially therewith. A plurality of generally quater round-shaped grooves
18 being inwardly directed are disposed at equal intervals in the
circumferential direction at opposite sides of the outer periphery of the
impeller 17. Rotation of the impeller 17 makes this group of grooves 18
move in the circumferential direction in a space formed on the outer
periphery of the pump chamber 16. A motor shaft 31 to be described
hereunder is inserted into the central axis of the impeller 17, whereby
the impeller 17 is rotatably driven by the motor shaft 31.
A liquid sealing portion 19 is formed in a position very close to the outer
peripheral surface of the impeller 17 on the inner periphery of an erected
wall of the pump head 15, with the erected wall defining the inner
peripheral surface of the pump chamber 16 in the casing 13. And
relatively, a gap portion 20 having suitable dimensions is formed on the
inner periphery excluding the liquid sealing portion 19. Furthermore, the
pump head 15 is provided with an intake port 21 which is disposed at the
initial end in the rotating direction out of the opposite sides in the
circumferential direction of the liquid sealing portion 19 and
communicates with the pump chamber 16. The intake port 21 communicates
with the outside of the housing 11 through an intake hole 22 opened in the
pump head 15.
On the other hand, the pump plate 14 is provided with a discharge port 23
disposed on the side opposite to the intake port 21 of the liquid sealing
portion 19 and communicates with the interior of the pump chamber 16. The
discharge port 23 is communicates with the interior of the housing 11
through a discharge hole 24 opened in the pump plate 14.
Generally annular groove paths 25 are recessedly formed extending from the
intake port 21 and the discharge port 23 respectively on the outer
periphery portions of end surfaces of the pump chamber 16 in the casing
13, both outer periphery portions of end surfaces of the pump chamber 16
being defined by the outer periphery portions of end surfaces of the pump
plate 14 and the pump head 15. Two deairing holes 26 are disposed at
generally central portions of the circumferential length of the groove
paths 25, the interiors of the groove paths 25 communicate with the
outside of the housing 11.
In this Embodiment 1, the pump head 15 is provided with an exhaust port 27,
which is disposed in the intermediate portion of the liquid sealing
portion 19, facing the outer peripheral surface of the impeller 17 and
communicating with the interior of the pump chamber 16. This exhaust port
27 communicates with the outside of the housing 11 through an exhaust hole
28 opened in the pump head 15.
On the other hand, in the motor portion 30, the motor shaft 31 having fixed
thereto the impeller 17, is disposed in the central axis of the housing 11
and is rotatably supported. An armature 32 and a commutator 33 are fixedly
mounted to the motor shaft 31. A plurality of magnets 34 are fixedly
provided on the inner peripheral surface of the housing 11 at equal
intervals in a circumferential direction thereof and opposed to the
armature 32. A brush holder stay 35 is fixedly mounted to the top end
portion in the housing in such a manner that brush holders 36 mounted
thereto are opposed to the commutator 33. Brushes 37 housed in the brush
holders 36 are in sliding contact with the commutator 33. An end bracket
38 is coupled and fixed to the top end portion of the housing 11. A
discharge pipe path 39 in communication with a fuel injection device, not
shown, is integrally projected from the end bracket 38 in a manner to be
disposed at the central portion and in communication with the interior of
the housing 11. The discharge pipe path 39 incorporates therein a check
valve 40. A relief valve 41 is integrally projected from the end bracket
38 in a manner to be disposed at a portion of the outer periphery of the
end bracket 38 and provides communication between the interior and the
exterior of the housing 11. The relief valve 41 incorporates therein a
depressurization valve 42.
Action of this Embodiment 1 will hereunder be described.
Rotation of the motor shaft 31 in the motor portion 30 makes the impeller
17, fixedly mounted thereto, be rotatably driven. When the impeller 17
rotates, the fuel is taken into the group of the grooves 18 formed on the
outer periphery of the impeller 17 through the intake port 21 and
discharged from the discharge port 23. The fuel discharge from the
discharge port 23 is discharged into the interior of the housing 11
through the discharge hole 24, and delivered to the fuel injection device,
not shown, through a discharge pipe path 39.
During this pump operation, the vapor produced in the groove paths 25 is
deaired to the outside of the housing 11 through the deairing holes 26
opened in the intermediate portions of the groove paths 25.
Furthermore, the exhaust port 27 is opened in the liquid sealing portion 19
in this Embodiment 1, whereby the vapor which has not been deaired through
the deairing holes 26 opened in the intermediate portions of the groove
paths 25 is passed through the exhaust port 27 and the exhaust hole 28 and
exhausted to the outside of the housing 11. At this time, pressure is
reduced in the exhaust port 27 of the liquid sealing portion 19, whereby
the vapor is exhausted effectively, so that the vapor can be prevented
from being produced in the vicinity of the intake port 21 after passing
the exhaust port 27. As the result, the intake port 21 is constantly
filled up with a fuel, so that the vapor lock can be prevented from
occurring.
FIG. 4 is the comparative graphic chart showing the decrease of the
discharge quantity of the fuel feed pump with the rise in the temperature
of the fuel, wherein a solid curve shows the case of this Embodiment 1 and
a broken curve shows the conventional example.
As shown in FIG. 4, in the case of this Embodiment 1 as compared with the
conventional example, the temperature at which the discharge quantity of
the pump is decreased and the temperature at which the vapor lock is
caused are both raised, so that the decrease of the discharge quantity of
the pump relative to the temperature of the fuel can be improved.
As described above, in the above Embodiment 1 of the present invention, the
exhaust port is opened in the liquid sealing portion, so that the vapor
can be exhausted effectively and the vapor lock can be prevented from
occurring.
Embodiment 2
The second embodiment of the present invention as shown in FIGS. 5 through
7 will hereunder be described.
Almost all of the construction of this Embodiment 2 is similar to that in
the above Embodiment 1.
In this Embodiment 2, an upper groove path 25A and a lower groove path 25B
are resessedly provided in generally annular shapes from the intake port
21 to the discharge port 23 respectively on the outer periphery portions
of the end surfaces of the pump plate 14 and the pump head 15, both of
which define the upper and lower outer periphery portions of the end
surfaces of the pump chamber 16 in the casing 13. A plurality of
downwardly directed deairing holes 26 are disposed in the generally
central portion of the circumferential length of the lower groove path 25B
and opened downwardly in a manner to provide communication between the
interior of the lower groove path 25B with the outside of the housing 11.
Furthermore, in this Embodiment 2, a deairing groove 127 is recessedly
provided in a generally circularly arcuate shape on the inner surface of
the pump plate 14 which is opposed to the upper surface of the impeller
17, the initial end portion 127a of this deairing groove 127 is in
communication with the generally central portion of the circumferential
length of the upper groove 25A, and the tail end thereof traverses the
liquid sealing portion 19 and is in communication with the inner end
portion of a deairing hole 128 to be described hereunder.
In this Embodiment 2, the deairing hole 128 is disposed in the vicinity of
the generally central portion of the liquid sealing portion in the casing
13, opened in a manner to be in communication with the outside of the
housing 11 from the pump plate 14 to the pump head 15, and the tail end of
the deairing groove 127 traverses the liquid sealing portion 19 and is
fluidally connected to the inner end portion of this deairing hole 128 on
the side of the pump plate 14.
Action of the Embodiment 2 will hereunder be described.
Rotation of the motor shaft 31 in the motor portion makes the impeller 17
fixedly mounted thereto be rotatably driven. When the impeller 17 rotates,
the fuel is taken into the group of grooves 18 formed on the outer
periphery of the impeller 17 through the intake port 21, and discharged
from the discharge port 23 by the centrifugal force. The fuel discharged
from the discharge port 23 is discharged into the interior of the housing
11 through the discharge hole 24, and passes through the discharge pipe
path 39 and is delivered to the fuel injection device, not shown.
During this pump operation, the vapor produced in the upper groove path 25A
is taken into the deairing groove 127 opened in the intermediate portion
of the upper groove path 25A, delivered into the deairing hole 128, and
then, deaired to the outside of the housing 11. Furthermore, the vapor
produced in the lower groove path 25B is directly deaired to the outside
of the housing 11 through the downwardly directed deairing holes 26 opened
in the intermediate portion of the lower groove path 25B.
Now, the vapor is lower in gravity than the fuel, whereby the vapor tends
to accumulate in the upper groove paths 25A out of the both upper and
lower groove paths 25A and 25B. Then, in this Embodiment 2, the deairing
groove 127 is opened to be in communication with the interior of the upper
groove path 25A, so that the vapor accumulated in the upper groove path
25A can be very effectively deaired from the groove path, i.e. the pump
chamber 16. Accordingly, the vapor is prevented from being produced in the
vicinity of the intake port 21 after the vapor has passed the discharge
port 23. As the result, the intake port 21 is constantly filled up with a
fuel, so that the vapor lock can be prevented from occurring.
Furthermre, the deairing groove 127 traverses the liquid sealing portion
19, whereby pressure in the liquid sealing portion is reduced and
production of the vapor due to the pressure reduction is eliminated, so
that the vapor lock can be further prevented from occurring.
Embodiment 3
A further embodiment of the present invention will hereunder be described
with reference to FIGS. 8 and 9.
FIG. 8 is the enlarged partially sectional view showing the Embodiment 3 of
the present invention, corresponding to FIG. 7.
The difference of this Embodiment 3 from the above Embodiment 2 resides in
that the deairing groove 127B is also provided on the side of the pump
head 15 and the tail end of this deairing groove 127B is connected to the
deairing hole 128. In this Embodiment 3, the downwardly directed deairing
holes 26 are omitted.
FIG. 9 is the comparative graphic chart showing the decrease of the
discharge quantity of the fuel feed pump with the rise of the temperature
of the fuel, wherein the solid curve shows the case of this Embodiment 3
and the broken curve shows the case of the conventional example.
As shown in FIG.9, in the case of this Embodiment 3 as compared with the
conventional example, the temperature at which the discharge quantity of
the pump is decreased and the temperature at which the vapor lock is
caused are raised, so that the discharge quantity of the pump relative to
the temperature can be improved.
As has been described hereinabove, according to the present invention, the
vapor can be exhausted effectively and the vapor lock can be prevented
from occurring.
The present invention should not be limited to the above embodiments,
various modifications may be adopted, and these modifications should be
included within the scope of the present invention.
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