Unit for delivering fuel from a supply tank to the internal combustion engine of a motor vehicle

A unit for delivering fuel from a supply tank to the internal combustion engine of a motor vehicle in which an electrical drive motor, which is embodied as an axial field motor, drives an impeller of a feed pump, which is embodied as a peripheral feed pump. In order to embody the delivery unit as flat as possible in the axial direction of the impeller, the rotor part of the axial field motor is disposed on the impeller, which carries the blades and which revolves in a pump chamber, and is combined with this impeller into one common element. The rotor windings of the rotor part can be disposed either inside a circle constituted by the blades of the feed pump or on the impeller radially outside the blades; the permanent magnets of the axial field motor are accordingly disposed in the housing, opposite the rotor windings.

BACKGROUND OF THE INVENTION 
The invention is based on a unit for delivering fuel from a supply tank to 
the internal combustion engine of a motor vehicle. German 
Offenlegungsschrift 33 035 709 discloses a delivery unit of this kind in 
which an electric drive motor and a feed pump driven to rotate by the 
motor are disposed in a common housing, which is connected on the suction 
side to the supply tank via a suction fitting and on the pressure side is 
connected via a pressure fitting to a feed line to the engine of a 
vehicle. The electric drive motor of the invention is embodied as an axial 
field motor, having a disk-shaped rotor part, guided on a shaft attached 
to the housing, that cooperates with permanent magnets disposed axially to 
it in a circle around the rotational axis of the rotor part. The rotary 
motion of the rotor part is transmitted to an impeller, which is embodied 
as the feed member of the feed pump and which is likewise guided on the 
shaft attached to the housing, which impeller aspirates the fuel via the 
suction fitting into a pump chamber, accelerates it, and supplies it to 
the pressure fitting at increased pressure. In order to be able to embody 
the measurements of the delivery unit as short as possible in the axial 
direction of the electric drive motor and feed pump, the rotor part and 
impeller have only a slight space between them or, as shown in FIGS. 9-12 
of the cited patent disclosure document, are disposed occupying a common 
radial limiting plane. 
The rotor part of the axial field motor and the impeller of the feed pump 
are combined in one disk-shaped element; involute-shaped feed fins, which 
have a curved course, are disposed on the face end of the rotor part and 
of the adjoining wall, which defines the pump chamber; during the rotating 
motion of the rotor, these feed fins feed fuel from a radially inner 
chamber to a radially outer chamber by increasing the pressure. The feed 
fins are constituted by means of conductor strips mounted on the rotor, 
which are charged via a commutator with an alternating, opposite electric 
potential. This commutator is embodied as a disk commutator, which is 
constituted by means of the radially internal part of the rotor; two 
commutator brushes, which are acted upon by differing electrical 
potential, are held in axial contact with one face end of the rotor by 
means of spring pressure. 
The known fuel delivery unit has the disadvantage, though, that by means of 
the involute-shaped feed fins on the rotor part and on the face end 
chamber walls, it has a relatively complicated design, which results in a 
high cost of manufacture. Moreover, the feed pump reaches proper 
efficiency only at high speeds, which are connected to a high noise 
emission, so that it does not satisfy current requirements of a delivery 
unit for an internal combustion engine. 
OBJECT AND SUMMARY OF THE INVENTION 
The unit for delivering fuel from a supply tank to the internal combustion 
engine of a motor vehicle according to the invention has an advantage over 
the prior art that by means of the embodiment of the feed pump as a 
peripheral pump, a high pump efficiency is already reached at low speeds 
of the impeller, which contains the rotor part; this slow rotation 
engenders relatively little noise, so that the delivery unit contributes 
to reducing the overall noise produced by the motor vehicle. 
In comparison to the known unit, the delivery unit according to the 
invention has a structurally simple design so that its cost of manufacture 
is comparatively lower. 
By means of embodying the commutator as a drum commutator having commutator 
brushes radially contacting the commutator, a long service life of the 
commutator segments can be achieved despite a very space-saving axial 
arrangement of the commutator. With suitable shaping of the permanent 
magnets or their one-sided arrangement on the face end of the impeller 
remote from the commutator, it is possible to make the peg which holds the 
drum commutator segments short, so that the commutator segments lead 
directly to the face end of the impeller, which contains the rotor part; 
thus the entire delivery unit can be embodied as flatter still and can 
therefore be inserted even into very flat fuel tanks. 
The integration of a fuel filter into the housing contributes to this very 
flat and compact design of the delivery unit, for which purpose this 
filter, which is advantageously likewise disk-shaped and which extends 
over the diameter of the impeller, constitutes a housing cover that closes 
the housing on its one face end. Consequently it is possible, with a very 
large fuel flow cross section, to integrate the fuel filter into the 
delivery unit without taking up additional space; moreover by means of 
this an additional housing cover can be omitted. 
In order to achieve a further simplification of the impeller, having the 
rotor part integrated into it, it is also possible to embody this as a 
simple spool and to alternatingly charge the elements of the stator 
attached to the housing, in which case the commutator disposed on the 
impeller could then be omitted, which would once again reduce the axial 
space of the unit; the stator elements can then be electronically 
commutated. 
The invention will be better understood and further objects and advantages 
thereof will become more apparent from the ensuing detailed description of 
preferred embodiments taken in conjunction with the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the arrangement shown in FIG. 1, a delivery unit 3 is inserted in a fuel 
supply tank 1 and communicates on the pressure side via a feed line 5 with 
an internal combustion engine 7 of a motor vehicle and supplies it with 
fuel during its operation. 
The first exemplary embodiment of the delivery unit 3 shown in FIG. 2 is 
embodied of an electric axial field motor 9 and a peripheral pump 11 
driven by it disposed together in a common, cylindrical housing 8. The 
delivery unit 3 has an impeller 15, which is disposed on a shaft (13) 
attached within the housing 8 and which revolves in a cylindrical pump 
chamber 17. A rotor part 19 of the axial field motor 9 as well as feed 
elements of the peripheral pump 11 are disposed on the impeller 15, which 
is depicted in an extremely simplified manner in FIG. 3. To that end, on 
its axial face ends, the disk-shaped impeller 15 has radially outward 
pointing rotor windings 21, which are embodied as flat and which are 
constituted by means of winding paths disposed in the disk surface, which 
when charged generate an axial field and which are coated with an 
electrically nonconductive, fuel resistant material so that the individual 
rotor windings 21 are delimited against each other. A ring of blades 23 is 
disposed on the impeller 15, which blades 23 are disposed spaced apart 
from one another in the circumference direction of the impeller 15, are 
directed outward, and radially adjoin the rotor part 19, which contains 
the rotor windings 21; the blades 23 constitute the feed elements of the 
peripheral pump 11 and transition in the exemplary embodiment in a 
radially outward pointing direction into a ring 24, which encompasses the 
impeller 15. 
Furthermore, permanent magnets 25 are disposed inside the housing 8 in a 
circular arrangement around the rotational axis of the impeller 15 on 
opposite sides of the rotor windings 21, having an axially pointing 
magnetic field disposed on both sides of the impeller 15 so that the 
magnets adjoining one another and the magnets opposite one another, 
respectively, have an opposite Potential. These permanent magnets 25, also 
indicated in FIG. 3, are adjoined in the radially outward-pointing 
direction by a disk-shaped base body 27 in the housing 8 in a radial 
alignment with each of the permanent magnets and on opposite sides of the 
blades 23. A partial ring-shaped supply conduit 29, which runs around the 
rotational axis of the impeller 15 and which is open to the impeller 15, 
is provided in the face end of the housing that defines the pump chamber 
17 and is oriented toward the impeller 15. This supply conduit 29 begins 
on its one end at an inlet opening 31 and leads to an outlet opening 33 
disposed staggered from the inlet by an angular range of approximately 
300.degree. (shown staggered); during operation, the revolving impeller 15 
produces a hydraulic communication between the inlet opening 31 disposed 
in the one part of the base body 27 and the outlet opening 33 disposed in 
the opposite part of the base body 27 by means of the blades 23, which 
make possible fuel penetration from the one face end of the impeller 15 to 
the other. 
For an alternating charge of the rotor windings 21 on the impeller 15, it 
has a so-called drum commutator 35, which is constituted by means of a 
concentric peg 37, which axially protrudes from the one face end of the 
impeller 15, on whose circumferential face commutator segments 39 are 
disposed parallel to the axis of the impeller 15, connected electrically 
to the individual rotor windings 21. Two commutator brushes 41 disposed 
opposite each other in the housing 8 and acted upon by different electric 
potentials are held in contact with these segments 39 by means of the 
spring pressure of two pressing springs 43, or run on the commutator 
segments 39 during the rotary motion of the impeller 15 and the drum 
commutator 35 connected to it in a manner fixed against relative rotation. 
The housing is closed on its face end remote from the commutator 35 by 
means of a flat, disk-shaped fuel filter 45, which is inserted in the 
housing 8 such that a fuel collecting chamber 47 remains between the 
housing and the face end of a spacer disk 46 remote from the impeller 15, 
which disk fixes the position of the permanent magnets 25 and of the base 
body 27, so that the entire surface of the fuel filter 45 can be used as a 
flow cross section. 
The inlet and outlet openings 31, 33 are disposed respectively in the base 
body 27 so that the inlet opening 31 feeds into the fuel collection 
chamber 47 while the outlet opening 33 emerges on the opposite face end of 
the disk-shaped housing 8. 
The second exemplary embodiment shown in FIGS. 4 and 5 differs from the 
first exemplary embodiment shown in FIGS. 2 and 3 in terms of the 
arrangement of the rotor part and feed elements. 
In the second exemplary embodiment, the ring of the blades 23 is disposed 
adjoining the impeller 15, radially inward of the impeller part which 
carries the rotor windings 21. Accordingly, the ring 0f permanent magnets 
25 is also disposed radially adjoining the outward base body 27, which 
contains the supply conduits 29; the arrangement of the inlet and outlet 
openings 31, 33 in the base body 27, as well as the construction of the 
drum commutator 35, is achieved in a manner analogous to the first 
exemplary embodiment. The electrical lines lead through the respective 
blades 23 to make contact between the commutator segments 39 and the 
individual rotor windings 21. 
The delivery unit according to the invention functions as follows: Upon 
charging of the commutator brushes 41, the individual rotor windings 21 
receive an electric current, which, in interaction with the magnetic field 
generated by the permanent magnets 25, produces a torque on the impeller 
15 so that it moves in a rotational direction determined by the 
arrangement of the permanent magnets 25. In a known manner, this rotary 
motion of the impeller 15 achieves a delivery of fuel from the inlet 
opening 31 to the outlet opening 33 by means of the motion of the blades 
23 in the supply conduit 29; the fuel pressure is increased while flowing 
through the supply conduit 29 by means of the impulse exchange between the 
fuel flowing in the supply conduit and that accelerated in the impeller. 
The fuel from the supply tank 1, which is at a low pressure, is taken in 
via the fuel filter 45 and delivered to the internal combustion engine 7 
at an increased pressure via the supply line 5 connected to the outlet 
opening 33. 
It is consequently possible in a structurally simple manner to transfer the 
advantages of an axial field motor, which is designed as flat, to a 
peripheral pump and thus to preserve a delivery unit designed to be very 
small in the axial direction, whose delivery output and noise emission 
meet the high demands made of modern fuel delivery units. 
The foregoing relates to preferred exemplary embodiments of the invention, 
it being understood that other variants and embodiments thereof are 
possible within the spirit and scope of the invention, the latter being 
defined by the appended claims.