GB1569842A

GB1569842A - Electrically driven fuel pump

Info

Publication number: GB1569842A
Application number: GB469177A
Authority: GB
Original assignee: Pierburg GmbH
Current assignee: Pierburg GmbH
Priority date: 1976-02-07
Filing date: 1977-02-04
Publication date: 1980-06-25
Also published as: FR2340463B3; BR7700728A; DE2604849A1; FR2340463A1

Description

(54) ELECTRICALLY DRIVEN FUEL PUMP (71) We, PIERBURG GMBH & Co KG, a Company duly organised under the Laws of the Federal Republic of Germany, of Leuschstrasse 1, 4040 Neuss, Federal Republic of Germany, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a fuel pump driven by an electric motor.

Fuel pumps of this general kind are already known which have motors with drum-type rotors.

But these known pumps are bulky in construction and have comparatively high hydraulic losses. Furthermore, they do not efficiently utilise the cooling effect for the electric parts which can be derived from the flowing fuel.

The intention in the present invention is to provide a fuel pump of this general kind, driven by an electric motor whose rotor is immersed in the liquid fuel, but which is free from the disadvantages mentioned above of the known pumps and which conveys the liquid fuel with a higher hydraulic efficiency.

According to the invention there is provided a fuel pump driven by an electric motor and comprising a housing having a fuel inlet and a fuel outlet, there being a stator carried on the housing wall and co-operating with said stator, a disc rotor, the stator and the rotor being immersed in the fuel within the housing so as to be cooled thereby and with the fuel occupying a radially extending annular working gap between the rotor and stator, and wherein the disc rotor acts as or is equipped with fuel conveying means whereby fuel is transferred from said inlet to said outlet when the disc rotor turns.

On first thoughts it might appear that using a disc rotor inside a space which is filled with a liquid must involve the disadvantage that for a given pump output the rotor disc has to have a comparatively large diameter and consequently hydraulic losses arising from turbulence are comparatively high.

But the present invention makes use of several advantageous effects. In the first place a disc rotor immersed in a liquid is easier to cool than a drum rotor. Furthermore the hydraulic flow conditions in the region of a disc rotor can be utilised to particularly good effect in helping to convey the fuel.

What has been said above applies not only to pumps in which the motor winding is on the rotor, the field magnets being fixed to the housing, but also to pumps in which the field magnets rotate, the motor winding or windings being fixed to the surrounding housing.

In fuel pumps which do not have to give a very high delivery pressure, usually 0.2 to 0.3 metres water gauge, and/or which do not have to provide any sucking effect, a centrifugal impeller is usually used. In pumps of this kind a particularly good conveying effect is obtained if the impeller blades extend radially outwards essentially as far as the outer periphery of the rotor on which they are mounted.

In pumps of this kind the rotor blades can be constructed in combination with the motor windings or magnets. In particular the blades can be combined integrally with the rotor, on one or both sides, or they can be fixed to the rotor by known jointing methods.

On the other hand, in fuel pumps which have to deliver comparatively high outlet pressures, usually between 1.5 and 6.0 atmospheres gauge, and/or which have to give a good suction for starting purposes, a vane pumpl of the positive displacement kind can be used, to good effect, or some other conventional kind of positive displacement pump.

In particular, a 'self-priming' capability is necessary when the pump is empty and sometimes also its inlet pipe, so that the pump has to suck fuel all the way from the fuel tank.

Where the fuel is conveyed by a vane pump, the rotating parts may be mounted axially on the disc rotor, that is to say radially inwards of the motor winding or magnet.

It is best to arrange that the rotating parts of the pump rotate with the rotor of the motor, and the gap between the rotating pump parts and the stationary pump part, or parts, should occupy a plane perpendicular to the axis of rotation of the motor.

In this case the gap between the rotary part or parts of the pump and the stationary part or parts can be kept very small by using axially thrusting springs and/or by utilising the electromagnetic forces acting on the motor winding and magnet, and/or by utilising hydraulic pressure differences in the flowing liquid. At this gap the parts in effect slide over each other. Furthermore, with this arrangement abrasion of the sliding parts does not change the width of the gap.

It should be emphasized that the constructional features described above can be applied to motors with disc rotors, irrespective of whether the magnets or windings are mounted on only one side or on both sides of the rotor.

In regard to motors which take de current, the winding should rotate, rather than the magnet. The commutator is best mounted near the middle of the rotor. If a vane pump is used, the commutator should be mounted on the face of the rotor away from the pump. A conventional flat commutator is best used, in which the working faces of the commutator segments extend radially.

With this arrangement the brush springs thrust the rotor axially, when the pump is being started up, keeping the gap small between the stationary and the moving parts of a vane pump, or the like, or the gap between the impeller blades and the housing, in the case of a centrifugal impeller pump, improving the starting behaviour of the pump.

Once the pump has gathered speed the magnetic or hydraulic forces reinforce the effect.

In regard to cooling of the electric parts, the flowing liquid can be utilised, either the main stream or a subsidiary stream, by easily devised constructional means, to cool the electric windings, irrespective of whether they rotate or not, and to cool the rotor bearings. Furthermore, the flow paths of the liquid must be arranged so that the commutator brushes, if a commutator is used, are not lifted by hydraulic thrusts from the surface of the commutator, although a sufficient flow of liquid must be maintained, at this location, to provide the necessary cooling.

If the motor is driven by ac current, or by 3-phase current, the magnets of the motor should rotate.

The invention will now be described in greater detail on the basis of the examples represented diagramamtically in the drawing, in which: Figure 1 is a section through a fuel pump according to the invention, with a disc rotor which functions as a centrifugal impeller: Figure 2 is a front view of the pump; and Figure 3 shows a fuel pump in which the fuel is conveyed by a vane pump of the positive displacement type.

In Figure 1 a housing 1 contains a disc rotor 41 with a shaft 3 rotating in two bearings 2. Fixed to the disc rotor 41 is a centrifugal impeller 5, or the disc rotor itself can function as a centrifugal impeller. The stator winding 61 of the electric motor is situated inside and carried on the wall of the housing 1. The motor magnets 71 are fixed to the disc rotor 41. The housing 1 has a fuel inlet 81 and a fuel outlet 91.

The shaft 3 has an axially locating bearing for its impeller end, this bearing acting so that an axial thrust applied towards it keeps the gap 10 constant between the impeller blades 5 and the inner surface of the housing 1. Figure 2 represents diagrammatically a possible arrangement for the fuel inlet and outlet 81, 91.

Tn the example shown in Figure 3, the motor winding 62 is on the disc rotor 42, the motor stator magnets 72 being carried on the wall of the housing. Fixed to the shaft 3 are the rotating parts of a vane pump 12, the stationary part 13 of the vane pump being fixed to housing 1.

The shaft 3 is axially mobile in its bearings 2. The gap 101 between the rotating parts and the stationary part of the vane pump 12 is kept very small, that is to say, there is practically no gap at all, by the effect of axial thrusts acting on the disc rotor 42. The origin of these thrusts has already been described. For example, an axial thrust can be applied by an end-spring 16.

A conventional flat commutator 14 is fixed to the disc rotor 42. The brushes are thrust against the face of the commutator by springs 15. The inlet and outlet of the pump, which in reality are separate from each other, are represented diagrammatically at 82, 92.

Claims

WHAT WE CLAIM IS:

1. A fuel pump driven by an electric motor and comprising a housing having a fuel inlet and a fuel outlet, there being a stator carried on the housing wall and co-operating with said stator, a dise rotor, the stator and the rotor being immersed in the fuel within the housing so as to be cooled thereby and with the fuel occupying a radially extending annular working gap between the rotor and stator, and wherein the disc rotor acts as or is equipped with fuel conveying means whereby fuel is transferred from said inlet to said outlet when the disc rotor turns.

2. A fuel pump according to claim 1, characterised in that the fuel-conveying means is a centrifugal impeller fixed to the disc rotor and having blades extending out to the periphery of the disc.

3. A fuel pump according to claim 1, characterised in that the disc rotor itself functions as a centrifugal impeller.

4. A fuel pump according to claim 1, characterised in that the fuel-conveying means are the rotating parts of a vane pump, which parts are mounted axially on the disc rotor.

5. A fuel pump according to claims 1 and 4, characterised in that a gap between rotating parts and stationary parts of the vane pump occupies a plane perpendicular to the axis of rotation of the disc rotor.

6. A fuel pump according to claim 5, charactrised in that one or more springs thrust rotating parts axially towards stationary parts of the pump.

7. A fuel pumpl according to claim 5, characterised in that a fuel flow guide builds up a pressure in the fuel which thrusts rotating parts axially towards stationary parts of the pump.

8. A fuel pump according to claim 5, characterized in that electromagnetic thrust is utilized to maintain the gap between rotating parts and stationary parts of the pump.

9. A fuel pump according to claim 5, characterised in that the disc rotor carries a winding of the motor, a commutator of the motor being a flat commutator fixed to the disc rotor, and including springs for thrusting against the commutator and serving also for brushes thrusting rotating parts axially towards stationary parts of the vane pump.

10. A fuel pump substantially as hereinbefore described with reference either to Figures 1 and 2 or to Figure 3 of the accompanying drawings.