CA2321608A1

CA2321608A1 - Electric fuel pump and pump mechanism for a fuel pump

Info

Publication number: CA2321608A1
Application number: CA 2321608
Authority: CA
Inventors: Klaus Gebert
Original assignee: Kautex Textron GmbH and Co KG
Current assignee: Kautex Textron GmbH and Co KG
Priority date: 1999-10-07
Filing date: 2000-10-02
Publication date: 2001-04-07
Also published as: JP2001132677A; EP1091472A2; DE19948171A1

Abstract

An electric fuel pump has at least one pump mechanism in the form of a side-channel pump mechanism, and a dc motor for driving the pump mechanism. The dc motor is an electronically commutated motor with a permanent-magnetic rotor. Parts of the stator can at least partially pass through the pump housing. The pump mechanism and the motor form respective separate units and the pump mechanism as a unit can be releasably connected to the dc motor.

Description

The invention concerns an electric fuel pump and a pump mechanism for a fuel pump.
An electric fuel pump may typically comprise at least one pump mechanism which for example may be in the form of a side-channel pump mechanism, with an electronically switched do motor for driving the pump mechanism. The pump may have a pump housing with at least one inlet and at least one outlet, while there is at least one pump impeller mounted rotatably in the pump housing and at the same time forming the rotor of the do motor.
it will be noted that fuel pumps are generally in the form of single-stage or dual-stage units, either in the form of positive-displacement pumps or in the form of flow or turbine pumps, wherein the pump mechanism is generally driven by way of a do motor. The pump mechanism and the electric motor are combined in a housing with an inlet and an outlet, the pump mechanism drawing in the fuel through the inlet and pumping it through the do motor to the outlet. In that situation the motor is cooled by the fuel flowing through the unit. The do motors which are usually employed in such a case involve do motors with separate excitation with permanent magnets and which are operated either on 12V or 24V
voltage. The pump mechanisms used are typically for example toothed ring pump mechanisms, side-channel pump mechanisms, peripheral channel pump mechanisms, vane or roller pump mechanisms and screw or axial pump mechanisms.
Fuel pumps of such a kind require a comparatively large installation volume, more particularly they require a considerable installation height. In principle however the dimensions of an electric fuel pump should be as small as possible so as to ensure that the components required are assembled in a compact and space-saving manner, to constitute what can be referred to as the tank installation unit. The term tank installation unit is generally used to designate a fuel delivery unit which includes all components required for the reliable supply of fuel to an engine. The dimensions of a fuel pump can be reduced to a limited extent by virtue of the choice of smaller pump diameters. A reduction in the pump diameter however entails higher speeds of pump rotation which are required to achieve the same delivery. High speeds of rotation however involve higher levels of thermal and mechanical stress for motor and pump components as well as higher levels of acoustic emissions. This means that minimising the dimensions of a fuel pump is to be implemented in part only at the expense of the robustness and longevity thereof.
On the other hand a reduction in the dimensions of fuel pumps is often desirable, having regard to the external contour of a tank with which such a pump is to be used. Particularly when the fuel tank involved is a blow-molded plastic tank, the tank enjoys a particular degree of flexibility in regard to the configuration thereof. Different locations for installation of tanks in a vehicle mean that there are very different tank design configurations which however must take account of fitments which are disposed in the tank. In that respect particular significance is to be attributed to the dimensions of a fuel pump to be fitted to the tank.
In order to reduce the installation height of fuel pumps and in order to reduce the number of moving parts of such electric fuel pumps, the impeller of the pump may be designed at the same time as the rotor of the electric motor driving the pump. An electric fuel pump of that kind is to be found for example in JP 63-120888 A, Patent Abstracts of Japan, M-748, 1988, Volume 12, No 371. That design of electric fuel pump provides that a plurality of windings pass through the impeller of the pump or the rotor of the motor, with the windings being put under voltage in the usual fashion by way of a brush and a commutator. A similar electric fuel pump is also to be found for example in DE 43 41 564.
Reference may also be made to German laid-open application (DE-OS) No 20 12 560 disclosing still another similar electric fuel pump in which the rotor is in the form of a permanent-magnetic rotor and the do motor is of a brushless configuration with magnet-controlled external commutator.
The use of a brushless do motor is proposed in that specification from points of view related to safety and wear, but nonetheless it will be apparent that a saving is additionally made in respect of axial installation

2 height, by virtue of omission of the otherwise usual commutator with brushes.
Attention may also be directed to DE 197 52 884.8 for example which discloses another form of fuel pump in which the electric motor is also a brushless design, to achieve an extremely flat structure in the axial direction, while its rotor is formed by the impeller of the delivery pump unit. The pump impeller is contained in a cylindrical pump chamber with radially extending, axially mutually spaced side walls and a peripheral wall which connects the two side walls together along their circular periphery.
The impeller is disposed in opposite relationship to the side walls with a very small gap in relation to the respective ones thereof, and the inside surface of a stator formed by a grooved lamination assembly forms the peripheral wall of the pump chamber. The pump mechanism of that pump is in the form of a side-channel pump mechanism and the two mutually axially spaced side walls are each provided with groove-like side channels which are open towards the pump chamber and which extend concentrically with respect to the axis of the impeller.
That design configuration is advantageous in terms of the requirement for a small axial structural height. In addition, the outside diameter of the electric fuel pump, which is increased by virtue of that structural design, is also advantageous in regard to improving the efficiency of the pump.
It will be noted however that production of the pump housing is an extremely complicated and expensive procedure as the pump housing in part forms both the stator and also in part the flow passages or ducts of the side-channel pump mechanism. In particular, the mutually contacting surfaces of the impeller and the pump housing portions forming the side channels, that is to say the sliding or bearing surfaces of the housing, must be produced with the maximum possible degree of flatness and evenness and the smallest possible roughness depth in order to minimise the axial play and clearance of the pump and thus any leakage losses. With the integral configuration of hydraulically operative parts of the pump housing and the electric motor stator, the surface treatment thereof is extremely

3 complicated and expensive, having regard to the complex contour of the component involved.
In accordance with the present invention there is provided an electric fuel pump comprising at least one pump mechanism including a pump housing having at least one inlet and at least one outlet, at least one pump impeller and means mounting the impeller rotatably in the pump housing and an electronically commutated do motor for driving the pump mechanism and having a stator and a rotor which is formed at the same time by the impeller, wherein the pump housing is partially penetrated by parts of the stator.
As will be seen from a description hereinafter of preferred embodiments of the invention, the arrangement in accordance with the invention affords a structural separation between the do motor and the pump housing, which latter can thus be produced separately and can thus be optimised in terms of its structure in regard to the required surface quality of the sliding or bearing surfaces thereof. Such an electric fuel pump design configuration in accordance with the invention also affords the advantage that the do motor and the pump mechanism can be made available as mutually separable units.
In accordance with a preferred feature of the fuel pump the pump housing, preferably at the pressure side, has a plurality of peripheral openings which are so arranged in relation to the impeller that they permit magnetically permeable extension portions of the stator to engage into the pump housing in such a fashion that a magnetically operative gap is formed between the impeller and the stator extension portions. That structure provides for guidance of both the magnetic flux in the form of a radial gap arrangement and also the flow of fuel. It will be appreciated that the fuel also flows through the do motor for cooling thereof. The structural combination of the pump impeller and the motor rotor is in effect detached by virtue of the partial interpenetration of the stator and the pump housing, with the stator and the pump housing forming separate components.

4 A preferred feature of the invention provides that the extension portions of the stator extend axially, that is to say in parallel relationship with and concentrically with respect to the axis of the impeller.
It will be noted at this point that an electronically switched do motor whose stator is of a design configuration as set forth hereinbefore is disclosed for example in US patents Nos 4 949 000, 4 837 474, 4 745 345,

5 659 217 and 5 874 797 to Petersen, to which attention is directed for incorporation herein of the full content thereof. A do motor of that kind involves an extremely small axial height, the motor is brushless and the rotor of the motor does not have any electrical terminals so that such a motor is ideally suited to use in an electric fuel pump. In particular the electronically switched do motor described in US patent No 5 659 217 is in the form of a radial gap motor of extremely shallow structure while being of comparatively large diameter.
In accordance with a further preferred feature of the invention the openings in the pump housing are arranged arcuately and concentrically with respect to the impeller and the diameter of that arrangement is larger than the inside diameter of the enclosed impeller so that the magnetically permeable extension portions of the stator embrace the pump impeller as a rotor.
A further preferred embodiment of the pump mechanism according to the invention provides that a ring of permanent-magnetic material encloses the impeller, while in a further preferred feature the ring is mounted axially displaceably with respect to the pump impeller. A loose arrangement of the ring and the impeller relative to each other in that way represents a simplification in terms of assembly.
In that arrangement it is preferably provided that the impeller and the ring of permanent-magnetic material co-operate in positively locking non-rotatable relationship with respect to each other.
Preferably, the pump housing is formed by disks respectively providing the side channels, wherein the disks can be fixed at a spacing relative to each other by way of at least one spacer ring. The advantage of such an arrangement is that all the individual parts of the pump mechanism can be produced and machined by grinding and lapping procedures. Those procedures afford a greater degree of flatness and smoothness at their surfaces and a lesser depth of roughness in respect of the sliding or bearing surfaces of the housing, as well as greater flatness and a lower depth of roughness in respect of the impeller which is in the form of a vane impeller.
That configuration also affords lower levels of leakage and an improved fuel delivery characteristic. Finally, at the same time a cost advantage is to be expected as the pump housing and the impeller do not have to be machined by turning processes. The production tolerances to be achieved are overall smaller.
It will be noted that, instead of a spacer ring as referred to above, annular grooves can be provided in the disks, to receive the magnetic ring.
Further in accordance with the invention there is provided a pump mechanism for a fuel pump which has a do motor as a flow pump having a i5 multi-part pump housing having at least one inlet and at least one outlet, at least one impeller, means rotatably supporting the impeller in the pump housing, wherein the pump mechanism forms a separate unit, and further including means for releasably connecting the pump mechanism to the do motor of a fuel pump.
As will be seen in greater detail hereinafter, that provides that the motor on the one hand and the pump mechanism on the other hand occur as units which can thus be handled separately and which can also be separately subjected to operational testing and checking. Hitherto the usual practice was for electric fuel pumps to be checked in production in the form of a complete unit with a motor in a fuel substitute for testing purposes.
The residual fuel which in those procedures then remains in the housings repeatedly gave rise to problems in subsequent procedures, for example upon integration into the delivery unit or into a tank. The pump mechanism according to the invention in contrast can be subjected to functional testing and checking without the motor and the associated electronics, while the residual fuel can be removed from the pump housing before assembly to the motor.

6 Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:
Figure 1 is a view in longitudinal section through an electric fuel pump according to the invention, Figure 2 is a simplified diagrammatic perspective view of an electronically commutated do motor of the electric fuel pump according to the invention, Figure 3 is a diagrammatic exploded view of a pump mechanism in accordance with a first embodiment of the invention, and Figure 4 is a diagrammatic exploded view of a pump mechanism in accordance with a second embodiment of the invention.
Referring now to Figure 1, an electric fuel pump according to the invention as illustrated therein comprises a hydraulic part and an electric part, with the hydraulic part being formed by a pump mechanism generally indicated by reference numeral 1 while the hydraulic part is formed by an electronically switched do motor which is generally indicated by reference numeral 2 and which for the sake of convenience will be referred to hereinafter in this description as the motor 2. As already mentioned above, the precise structure and mode of operation of the motor in various different configurations are to be found in US patents Nos 4 949 000, 4 837 474, 4 745 345, 5 659 217 and 5 874 796 to Petersen, the disclosure of which is to be suitably incorporated herein by virtue of reference thereto.
The pump mechanism 1 and the motor 2 are each in the form of units which can be releasably connected together, as shown they are secured to each other by way of screws 3 in a casing 4.
The motor 2 has a generally plate-shaped stator which is generally identified by reference numeral 5 in Figure 1 and which has an annular laminated stator assembly 6. The laminated stator assembly 6 forms magnetically permeable extension portions 7 which as shown in Figure 2 each extend in a finger-like configuration in the axial direction of the assembly, that is to say in parallel relationship with the axis of rotation of the impeller of the pump and the rotor of the motor. In their base or root region the extension portions 7 are each surrounded by field windings

7 ' CA 02321608 2000-10-02 diagrammatically indicated at 8 in Figure 1. The stator 5 and the extension portions 7 are of such a configuration that a permanent-magnet rotor can fit into the hollow space enclosed by the extension portions 7, forming a magnetic gap. A rotating electromagnetic field can be produced by way of the field windings, which drives the rotor across a radial gap.
As can be seen for example from Figures 1 and 3, the electric fuel pump according to the invention is designed in such a way that the extension portions 7 of the stator 5 partially pass through the two-part pump housing which is identified by reference numeral 9. The pump i0 mechanism 1 which as shown in Figure 3 is in the form of a dual-stage side-channel pump mechanism comprises a first housing portion 10 with a fuel inlet 11, a second housing portion 12 with a fuel outlet 13, and a pump impeller in the form of a vane impeller 14 mounted rotatably between the housing portions 10 and 12. The impeller 14 co-operates with a first side i5 channel 15 of the first housing portion 10 and a second side channel (not shown) in the second housing portion 12. The side channels extend substantially concentrically with respect to the axis of the impeller 14. As already mentioned above, the pump mechanism shown in Figure 3 is of a two-stage design configuration, and it will be appreciated that the pump 20 chamber formed by the pump housing 9 is cylindrical.
The impeller 14 of the pump mechanism is enclosed by a magnetic ring 16 having permanent-magnetic properties. The magnetic ring 16 can be composed of magnets which are arranged in a discretely distributed array around the periphery of the impeller 14. It will be appreciated 25 however that the ring 16 can also be formed in one piece from plastic material with suitably magnetised ferrite portions incorporated therein.
The second housing portion 12 is provided with peripherally arcuately arranged openings 17 therethrough, as can be particularly clearly seen from Figures 3 and 4. The contour of the openings 17 corresponds to the 30 contour of the extension portions 7 of the stator 5. The openings are arranged concentrically with respect to the impeller 14 and the inside diameter of that arrangement is slightly larger than the outside diameter of the impeller 14 enclosed by the magnetic ring 16, so that the magnetically

8 permeable extension portions 7 of the stator can extend into the pump housing 9, concentrically surrounding the magnetic ring 16 and the impeller 14. As noted above, the extension portions 7 extend axially and concentrically with respect to the axis of the impeller 14. In that way, formed between the extension portions 7 and the magnetic ring 16 is a magnetically effective gap in the form of a radial gap so that the impeller 14 performs both the function of the pump impeller and also acts as the rotor of the motor 2. This highly compact arrangement of the pump mechanism 1 and the motor 2 relative to each other also permits effective guidance for the flow of fuel which flows with a cooling action around the field windings 8 of the stator 5.
The housing portions 10 and 12 are of a circular or disk-shaped configuration, as can be seen for example from Figure 3, and it will be appreciated that the diameter thereof is larger than the diameters of the stator 5 and the impeller 14.
Referring now to Figure 4, in the embodiment of the pump mechanism 1 illustrated therein it is in the form of a dual-flow pump mechanism. With the pump impeller being of a dual-flow configuration, its thickness is markedly less than the thickness of a dual-stage impeller. The magnetic ring 16 however must be of a certain minimum thickness in order to achieve the desired output or in order to be able to apply a correspondingly high level of torque.
In order to achieve a simplification of the pump mechanism 1 according to the invention in terms of production processes and engineering, the embodiment of the pump mechanism 1 shown in Figure 4 provides that the housing portions 10 and 12 and also the impeller 14 and a spacer ring which is identified by reference 18 are in the form of flat disks. The magnetic ring i6 is arranged floatingly, that is to say axially displaceably, with respect to the impeller 14, while the magnetic ring 16 and the impeller 14 are connected together in positively locking relationship in the peripheral direction by way of entrainment portions indicated at 19 in Figure 4 on the impeller 14 and corresponding recesses indicated at 20 in the magnetic ring 16 so that the magnetic ring 16 and the impeller 14 are

9 guided one within the other in non-rotational relationship with each other, that is to say, so that they can rotate together with each other but they are not rotatable relative to each other. So that all components can be in the form of disks with the pump housing being of a suitable depth, the first housing portion 10 and the second housing portion 12 are screwed together with the interposition of the spacer ring 18. This arrangement affords the advantage that all the disk-shaped components can be subjected to finishing machining by lapping and grinding, whereby the housing sliding and bearing surfaces enjoy a greater degree of flatness and smoothness and a smaller depth of roughness in their surface. The recesses 20 in the magnetic ring 16 are so selected that the impeller 14 is axially centered in the magnetic ring 16 by way of the sliding surfaces of the first housing portion 10 and the second housing portion 12. As already indicated above and as will be readily apparent such an arrangement also affords cost advantages.
As an alternative to the structure shown in Figure 4, it is also possible for the magnetic ring 16 to be in the form of a component which can be fitted on to the impeller 14 by snap engagement or by latching or detent engagement.
As will be seen from the foregoing, the invention can provide an electric fuel pump of an improved structural configuration, while retaining the advantages of a design which is shallow in the axial direction, that is to say in the direction of the pump impeller axis. The electrically operated fuel pump can be of such a design configuration that it is relatively simple to manufacture and can be easily produced as a high-quality unit, as well as affording enhanced versatility of design options.
It will be appreciated that the above-described embodiments of the invention have been set forth solely by way of example and illustration of the principles thereof and that further modifications and alterations may be made therein without thereby departing from the spirit and scope of the invention.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed, are defined as follows:

1. An electric fuel pump comprising at least one pump mechanism including a pump housing having at least one inlet and at least one outlet, at least one impeller, and means mounting the impeller rotatably in the pump housing, and an electronically commutated do motor for driving the pump mechanism and having a stator and a rotor which is formed at the same time by the impeller, wherein the pump housing is adapted to be partially penetrated by parts of the stator.

2. A fuel pump as set forth in claim 1 wherein the pump mechanism is in the form of a side-channel pump mechanism.

3. A fuel pump as set forth in claim 1 wherein the parts of the stator are magnetically permeable extension portions and wherein the pump housing has a plurality of peripheral openings which are so arranged in relation to the impeller that they permit the magnetically permeable extension portions of the stator to engage into the pump housing in such a way that a magnetically operative gap is formed between the impeller and the stator extension portions.

4. A fuel pump as set forth in claim 3 wherein the pump housing has said peripheral openings at the pressure side thereof.

5. A fuel pump as set forth in claim 3 wherein said extension portions of the stator extend axially and concentrically with respect to the axis of the impeller.

6. A fuel pump as set forth in claim 3 wherein the openings are arcuate and arranged concentrically with respect to the impeller and the arrangement is of an inside diameter which is larger than the outside diameter of the enclosed impeller.

7. A fuel pump as set forth in claim 1 wherein the impeller has an enclosure means of permanent-magnetic material.

8. A fuel pump as set forth in claim 1 including a ring of permanent-magnetic material enclosing the impeller.

9. A fuel pump as set forth in claim 8 wherein the ring of permanent-magnetic material is mounted axially displaceably with respect to the pump impeller.

10. A fuel pump as set forth in claim 9 wherein the impeller and the ring of permanent-magnetic material co-operate in positively locking non-rotatable relationship with respect to each other.

11. A fuel pump as set forth in claim 2 wherein the pump housing is formed by disks respectively providing the side channels, and further including at least one spacer ring for holding said disks at a mutual spacing.

12. A pump mechanism for a fuel pump which has a dc motor as a flow pump, comprising a multi-part pump housing having at least one inlet and at least one outlet, at least one impeller and means rotatably supporting the impeller in the pump housing, wherein the pump mechanism forms a separate unit, and further including means for releasably connecting the pump mechanism to a dc motor of a fuel pump.

13. A pump mechanism as set forth in claim 12 wherein said dc motor is electronically commutated.

14. A pump mechanism as set forth in claim 12 wherein the pump mechanism is in the form of a side-channel pump mechanism.

i5. A pump mechanism as set forth in claim 12 wherein parts of the stator in the form of magnetically permeable extension portions extend through the pump housing, and wherein the pump housing has a plurality of peripheral openings which are so arranged in relation to the impeller that they permit the magnetically permeable extension portions of the stator to engage into the pump housing in such a way that a magnetically operative gap is formed between the impeller and the stator extension portions.

16. A pump mechanism as set forth in claim 15 wherein the pump housing has said peripheral openings at the pressure side thereof.

17. A pump mechanism as set forth in claim 15 wherein said extension portions of the stator extend axially and concentrically with respect to the axis of the impeller.

18. A pump mechanism as set forth in claim 15 wherein the openings are arcuate and arranged concentrically with respect to the impeller and the arrangement is of an inside diameter which is larger than the outside diameter of the enclosed impeller.

19. A pump mechanism as set forth in claim 12 wherein the impeller has an enclosure means of permanent-magnetic material.

20. A pump mechanism as set forth in claim 12 including a ring of permanent-magnetic material enclosing the impeller.

21. A pump mechanism as set forth in claim 20 wherein the ring of permanent-magnetic material is mounted axially displaceably with respect to the pump impeller.

22. A pump mechanism as set forth in claim 21 wherein the impeller and the ring of permanent-magnetic material co-operate in positively locking non-rotatable relationship with respect to each other.

23. A pump mechanism as set forth in claim 14 wherein the pump housing is formed by disks respectively providing the side channels, and further including at least one spacer ring for holding said disks at a mutual spacing.