Fuel pump having regenerative section provided with vent housing for voltex flow

A fuel pump comprises a regenerative pump section, a driving section and a housing, the regenerative pump section being provided with a vapor vent for discharging fuel vapor. The vapor vent communicates with an outside of the fuel pump through a vent housing for a vortex flow. The vent housing has a vent chamber, a tangential groove and a discharge hole. A vortex flow of the fuel including the fuel vapor generates in the vent chamber and flows from the tangential groove to the discharge hole. When the fuel vapor does not generate, the vortex phenomenon is enhanced so that an amount of the fuel discharged from the discharge hole is reduced. The vent housing may have a radial control groove communicating with a control hole in addition to the tangential groove.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
This invention relates to a fuel pump used for an automobile or the like, 
and more specifically to an improvement of a fuel pump driven by an 
electric motor, supplying fuel to an injector at a high pressure, and 
constituting a part of means for injecting fuel to an engine in response 
to signals from an electronic control device. 
(2) Description of the Prior Art 
A displacement pump has been hitherto mainly used for feeding fuel with a 
high pressure, a discharge pressure of the pump being about 2 or 3 
kg/cm.sup.2. The displacement pump, however, has disadvantages that high 
accuracy of working is required for obtaining a desired performance, thus 
resulting in a high cost, and the discharge pressure greatly pulsates due 
to the displacement type, thus resulting in high vibration and noise. 
It has been known for solving the aforesaid disadvantages to use a 
regenerative pump as a fuel pump. The regenerative pump used as the fuel 
pump is described in, for example, U.S. patent application Ser. Nos. 
362,855 filed on Mar. 29, 1982, now U.S. Pat. No. 4,451,213; 366,688 on 
Apr. 8, 1982, now abandoned; 377,546 on May 12, 1982; 369,426 on Apr. 19, 
1982; 370,350 on Apr. 21, 1982, now U.S. Pat. No. 4,478,550; 372,169 on 
Apr. 26, 1982, now U.S. Pat. No. 4,445,821; 372,377 on Apr. 27, 1982, now 
U.S. Pat. No. 4,403,910; 378,724 on May 17, 1982; 405,579 on Aug. 5, 1982; 
445,222 on Nov. 29, 1982 and 505,849 on June 20, 1983. 
When an automobile runs under a severe load condition such as running on a 
sloping road in high ground and in a high temperature, a fuel temperature 
in a fuel tank rises gradually, thus often resulting in occurrence of 
bubbles of fuel vapor in the fuel tank. Then, the fuel pump sucks not only 
fuel but also the bubbles through a suction port, or sucks only the fuel 
vapor in an extreme state, so that a rise in fuel pressure is not 
performed in the fuel pump. As a result, a vapor-lock phenomenon occurs 
and an engine stops. 
It has been known to provide the regenerative pump with a vapor vent midway 
of a pump passage in order to discharge the above-mentioned fuel vapor out 
of the fuel pump. The regenerative pump of this type can discharge vapor 
in a pump chamber during a starting operation of the pump, and further 
discharge vapor caused by cavitation during a normal operation of the 
pump. The conventional vapor vent, however, only connects the pump passage 
with the outside of the pump, thus it is inevitable that not a small 
amount of the fuel is discharged to the outside of the pump through the 
vapor vent even in case of including no fuel vapor. The fuel pump provided 
with the vapor vent is disclosed in, for example, U.S. Pat. No. 3,418,991. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide a regenerative fuel pump capable 
of discharging the fuel vapor out of the pump, preventing the vapor-lock, 
and reducing the fuel discharged through the vapor vent to the outside of 
the pump when the fuel vapor is not generated. 
To accomplish the aforesaid object, there is provided a fuel pump 
comprising a regenerative pump section, a driving section connected to an 
impeller of the regenerative pump section, and a housing enclosing the 
regenerative pump section and the driving section, the fuel pump being 
provided with a vapor vent midway of a pump passage extending from a 
suction port of the regenerative pump section to a discharge port thereof, 
wherein 
the vapor vent communicates with an outside of the fuel pump through a vent 
housing for a vortex flow, and 
the vent housing has a vent chamber of a substantially circular shape, a 
tangential groove provided with one end communicating with the vent 
chamber in a tangential direction to the vent chamber and other end 
communicating with the vapor vent, and a discharge hole provided with one 
end communicating with a center portion of the vent chamber and other end 
communicating with the outside of the fuel pump. 
Another feature of the invention is to provide a fuel pump wherein the 
regenerative pump section is provided with a control hole communicating 
with the pump passage and disposed at a downstream side of the vapor vent, 
and the vapor vent and the control hole communicate with the outside of 
the fuel pump through a vent housing. The vent housing has a vent chamber 
of a substantially circular shape, a tangential groove provided with one 
end communicating with the vent chamber in a tangential direction to the 
vent chamber and other end communicating with the control hole, a vent 
groove provided with one end communicating with the vent chamber in a 
radial direction to the vent chamber and other end communicating with the 
vapor vent, and a discharge hole provided with one end communicating with 
a center portion of the vent chamber and other end communicating with the 
outside of the fuel pump. 
The above and other features of the invention will become apparent from a 
reading of the detailed description of the preferred embodiments which 
make reference to the following set of drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, a fuel pump of this type is installed in liquid fuel 
in a fuel tank as of a vehicle. The fuel pump includes a substantially 
cylindrical housing 10, and the housing 10 has one axial end wall 13 and 
another axial end wall 14 each provided with an opening 11, 12. The fuel 
pump comprises a regenerative pump section 15 disposed in the housing 10 
and being in contact with the end wall 13, and an driving section or 
electric motor section 16 disposed in the housing 10 and arranged adjacent 
to the regenerative pump section 15. The electric motor section 16 is 
connected to the regenerative pump section 15 and drives the same. 
The regenerative pump section 15 includes a pump casing consisting of a 
first casing portion 18 and a second casing portion 21, the first casing 
portion 18 substantially closing the opening 11 provided on the end wall 
13, and the second casing portion 21 having an inner surface 19. The inner 
surface 19 of the second casing portion 21 and inner surface 17 of the 
first casing portion 18 define a pump chamber. 
A rotary shaft 25 extends coaxially with the housing 10 and is rotatably 
supported at its axial end 26 by a bearing 28 fitted into an axial central 
bore 27 provided on the second casing portion. The axial end 26 of the 
rotary shaft 25 passes through the pump chamber and has an axial end 
surface located in a central recess 31 formed on the inner surface 17 of 
the first casing portion 18. 
A disc-shaped impeller 32 is rotatably mounted on the rotary shaft 25 in 
the pump chamber. The impeller 32 has an axial central bore 33 (see FIG. 
2) adapted to be fitted over the one axial end 26 of the rotary shaft 25. 
A wall surface of the central bore 33 is formed with a pair of axial 
grooves 34 diametrically opposed to each other. A pin 36 having a circular 
cross-section extends through the axial end 26 of the rotary shaft 25, and 
two ends fitted into the pair of axial grooves 34 respectively. 
Accordingly, the impeller 32 is so mounted on the rotary shaft as to be 
movable in an axial direction and not rotatable with respect to the rotary 
shaft 25. 
The impeller has one axial end surface 38 facing the inner surface 17 of 
the first casing portion 18 and defining a first gap W.sub.1, and the 
other axial end surface 39 facing the inner surface 19 of the second 
casing portion 21 and defining a second gap W.sub.2. These gaps W.sub.1 
and W.sub.2 are actually very small, and exaggerated in FIG. 1 therefore. 
The central recess 31 provided on the first casing portion 18 defines a 
chamber 43 by cooperating with the end surface and a peripheral surface of 
the axial end portion 26. The axial central bore 27 provided on the second 
casing portion 21 defines a chamber 44 by cooperating with an axial end 
surface of the bearing 28 and the peripheral surface of the axial end 
portion 26 of the rotary shaft 25. As can clearly be seen in FIG. 2, the 
wall surface of the axial central bore 33 provided on the impeller 32 is 
formed with a second pair of axial grooves 45 diametrically opposed to 
each other. The chambers 43 and 44 communicate with each other through the 
second pair of axial grooves 45, so that the pressure balance can effect 
between the chambers 43 and 44. 
The impeller 32 has a peripheral portion defining a substantially annular 
pump passage 46 in the casings 18 and 21. The peripheral portion of the 
impeller 32 is formed with a plurality of radial blade grooves 47 arranged 
circumferentially with equally spaced relations. The impeller 32 shown in 
FIGS. 1 and 2 is of a closed-blade type, that is, bottom surfaces of the 
blade grooves 47 formed on one axial end surface 38 do not intersect with 
the other axial end surface 39, while bottom surfaces of the blades 47 
formed on the other axial end surface 39 also do not intersect with the 
one axial end surface 38. 
The pump passage 46 communicates with the liquid fuel in the fuel tank (not 
shown) through a suction port 51 provided on the first casing portion 18, 
and also communicates with a space within the housing 10 through a 
discharge port 52 provided on the second casing portion 21. 
The electric motor section 16 has two substantially arcuate permanent 
magnets 61 arranged coaxially with the rotary shaft 25 in the housing, an 
armature 62 fixedly mounted on the rotary shaft 25 and arranged coaxially 
with the permanent magnets 61, and a commutator 63 connected to the 
armature 62 and secured to the rotary shaft 25. The commutator 63 is in 
sliding contact with a brush 64 supported by a brush holder 66 secured to 
an end block 67. The end block 67 is arranged to substantially close the 
opening 12 of the housing 10. The end block 67 has a central recess 71 
formed on its axial end surface facing the space in the housing, and a 
second central recess 72 formed on a bottom surface of the central recess 
71. A wall surface of the second central recess 72 is formed with a 
plurality of grooves 73 arranged circumferentially with spaced relations. 
The grooves 73 each has an inclined bottom surface and an end which opens 
to a bottom surface of the second central recess 72. The end block 67 has 
a hollow projection 74 projecting outwardly from the other axial end 
surface, and a bore of the hollow projection 74 communicates with the 
second central recess 72. The hollow projection 74 is adapted to 
communicate with a fuel consumption system such as an engine (not shown). 
The other axial end portion 81 of the rotary shaft 25 is rotatably 
supported by a bearing 82. The bearing 82 is seated on a seat 83 formed by 
chamfering on the second central recess 72, and held in place by an 
annular retainer 85 disposed in the central recess 71. The retainer 85 has 
a plurality of holes 86 formed circumferentially with spaced relations. 
The rotary shaft 25 is held in place by the annular retainer 85. The 
rotary shaft 25 is held also axially in place by a spacer 87 mounted on 
the rotary shaft 25 and being in contact with one axial end surface of the 
bearing 82, and by a spacer 88 mounted on the rotary shaft 25 and being in 
contact with one axial end surface of the bearing 28. 
Referring to FIG. 3, there are clearly shown the first casing portion 18 
and a vent housing 7. The first casing portion 18 is provided with a vapor 
vent 6 at a somewhat upstream side of the half point of the pump passage 
46 extending from the suction port 51 to the discharge port 52, and 
further provided with a control hole 6' at a downstream side of the vapor 
vent 6. A diameter of the control hole 6' is smaller than that of the 
vapor vent 6. The vent housing 7 is secured, by adhesion, caulking or the 
like, to an opening side of the first casing portion 18. The vent housing 
is integrally made by resin molding, aluminium die casting or the like. 
Referring to FIG. 4, the vent housing 7 has a vent chamber 7d, a discharge 
hole 7a, a tangential groove 7b and a vent groove 7c. The vent chamber 7d 
is a substantially circular recess. The discharge hole 7a has one end 
communicating with a central portion of the vent chamber 7d and other end 
communicating with the outside of the fuel pump. The tangential groove 7b 
has one end communicating with the vent chamber 7d in a tangential 
direction to the vent chamber 7d and other end 7b' communicating with the 
control hole 6' provided on the first casing portion 18. The vent groove 
7c has one end communicating with the vent chamber 7d in a radial 
direction to the vent chamber 7d and other end 7c' communicating with the 
vapor vent 6 provided on the first casing portion 18. 
An operation of the fuel pump of the above construction will be described 
hereinunder. 
When an electric current is introduced from the electric source (not shown) 
to the brush 64, the armature 62 rotates. The rotation of the armature 62 
is transmitted to the impeller 32 through the rotary shaft 25, and the 
impeller 32 rotates in the clockwise direction as shown by an arrow in 
FIG. 2. The rotation of the impeller 32 allows the liquid fuel in the fuel 
tank to be introduced to the pump passage 46 through the suction port 51. 
The fuel introduced to the pump passage 46 is increased in pressure by the 
action of the blade grooves 47 of the impeller 32, and is discharged to 
the space in the housing 10 through the discharge port 52, and is further 
conducted to the fuel consumption system through an annular gap defined 
between the permanent magnets 61 and the armature 62, the holes 86 formed 
on the retainer 85, the grooves 73 formed on the end block 67 and the bore 
of the hollow projection 74. 
Nextly, an operational principle of the vent housing for a vortex flow will 
be explained by referring to FIGS. 5 and 6. During the normal running of 
the vehicle wherein the fuel is not vaporized, the fuel in the pump 
passage 46 partly discharged from both vapor vent 6 and the control hole 
6'. As shown in FIG. 5, the fuel discharged from the control hole 6', 
which is located at a higher pressure side than the vapor vent 6, 
constitutes a control flow flowing from the tangential groove 7b into the 
vent chamber 7d in the tangential direction with respect to the vent 
chamber 7d. On the other hand, the fuel discharged from the vapor vent 6 
constitutes a main flow flowing from the vent groove 7c into the vent 
chamber 7d in the radial direction with respect to the vent chamber 7d. 
The main flow has a larger flow rate than that of the control flow because 
the control hole 6' has a smaller diameter than that of the vapor vent. 
The control flow has a higher speed than that of the main flow because the 
control hole 6' is located at a higher pressure side, i.e. downstream 
side, than the vapor vent. In this condition, the main flow from the vent 
groove 7c is altered in direction by the action of the control flow from 
the tangential groove 7b and becomes a vortex flow 9. The more the vortex 
flow approaches the center of the vent chamber 7d, the more the fuel 
pressure of the vortex flow 9 falls. As a result, an amount of fuel 
discharged from the discharge hole 7a can be reduced. 
In contrast, when the fuel is partly vaporized, the fuel in the pump 
passage 46 is not sufficiently increased in pressure. Accordingly, 
pressure difference between the vapor vent 6 and the control hole 6' is 
relatively small, and the main flow from the vent groove 7c is hardly 
affected by the control flow from the tangential groove 7b. In this 
condition, the combination of the main flow and the control flow 
constitutes a flow 9' flowing in a substantially radial direction as shown 
in FIG. 6, and the flow 9' including the fuel vapor can be discharged from 
the discharge hole 7a through the vent chamber 7d with a small resistance, 
resulting in easy discharge of the fuel vapor. It is understood that an 
amount of the fuel discharged from the discharge hole 7a depends upon 
section areas of the tangential groove 7b and the vent groove 7c and the 
fuel pressure difference between the tangential groove 7b and the vent 
groove 7c. In this embodiment, a section area of the tangential groove is 
taken to be smallest possible, so that a compact construction is obtained. 
Referring to FIG. 7, characteristic curves of the fuel pump are taken under 
conditions that input voltages of the motor of the fuel pump are 8 and 12 
V. The abscissa indicates a flow rate of the fuel pump, and the ordinate 
indicates a discharge pressure of the fuel pump. The fuel pump including 
the vent housing allows the flow rate to be increased in the same 
discharge pressure as compared with the fuel pump including no vent 
housing. This advantage is enhanced in the condition of 8 V in input 
voltage, this condition corresponding to a starting condition in a low 
temperature. In addition, in an examination that the vapor-lock is 
compulsorily generated and thereafter a time required for re-starting the 
fuel pump is measured, it is found that the fuel pump including the vent 
housing gives a good performance. 
Referring to FIGS. 8 and 9, another embodiment of the invention includes a 
vent housing provided with a leaf spring at an outlet of the tangential 
groove. In FIG. 8, the vent housing 7 has a leaf spring 8 and a stopper 7e 
for the leaf spring 8. The stopper 7e has an inner surface smoothly 
connected to an inner surface of the vent chamber 7d, and a tip end 
projecting at the outlets of the vent groove 7c and the tangential groove 
7d but so as not to close both of the grooves. The leaf spring 8 has a 
free end covering over the outlet of the tangential groove 7b. When the 
fuel vapor generates, the pressure in the tangential groove 7b is so low 
as not to overcome a spring force of the leaf spring 8, that is, the 
control flow from the tangential groove is not generated. Accordingly, 
only the main flow from the vent groove 7c exists in the vent chamber and 
the fuel vapor flows along a flow 9a in a radial direction or straight 
with no resistance, resulting in effective discharge of the fuel vapor to 
the outside of the fuel pump. 
In contrast, when the fuel vapor does not generate, i.e. the vehicle is 
under a normal running, the pressure in the tangential groove 7b overcomes 
the spring force of the leaf spring 8 as shown in FIG. 9, so that the leaf 
spring 8 is pressed against an outer surface of the stopper 7e and the 
outlet of the tangential groove 7b is opened to the vent chamber 7d. The 
main flow from the vent groove 7c is altered in direction by the action of 
the control flow from the tangential groove 7b and becomes a vortex flow 
9b. Accordingly, an amount of the fuel discharged from the discharge hole 
7a can be reduced, like the case shown in FIG. 4. 
Another embodiment of the invention includes a vent housing provided with a 
tangential groove but no other groove. Referring to FIG. 10, the first 
casing portion 18 is provided with a vapor vent 6 but no control hole. The 
vent housing 7' has a vent chamber 7d' of a substantially circular shape, 
a tangential groove 7b" provided with one end communicating with the vent 
chamber 7d' in the tangential direction to the vent chamber 7d' and other 
end communicating with the vapor vent 6, and a discharge hole 7a' provided 
with one end communicating with the center of the vent chamber 7d' and 
other end communicating with the outside of the fuel pump. When the fuel 
vapor is not generated, a vortex flow in the vent chamber 7d' is enhanced, 
and thus an amount of the fuel discharged from the discharge hole 7a' is 
reduced. When the fuel vapor is generated, a vortex flow becomes weaker, 
and thus an amount of the fuel discharged from the discharge hole 7a' is 
increased. 
FIG. 11 shows further another embodiment of the invention. The vent housing 
7' includes a ring 5 provided with four communication holes 5a in the vent 
chamber 7d'. The ring 5 is disposed to be concentric with the vent chamber 
7d', and thus the vent chamber 7d' is divided into two spaces. The two 
spaces communicate with each other through the communication holes 5a. In 
this embodiment, an amount of the fuel discharged from the discharge hole 
7a' is relatively reduced as compared with the embodiment shown in FIG. 
10. 
According to the invention, there is provided a fuel pump capable of 
effectively discharging the fuel vapor when the fuel vapor is generated 
and reducing discharge of the fuel from the vapor vent when the fuel vapor 
is not generated. Further, the fuel pump according to the invention 
realizes high reliability in addition to the above advantage because the 
vent housing has no movable part.