GB2052170A - Improvements in or relating to fuel supply units - Google Patents

Abstract

A method for the production of a fuel-resistant fuel supply unit, preferably an electrically driven fuel pump, and also a fuel supply unit are proposed, wherein resin break-aways may be avoided at the armature winding. For producing such a fuel- resistant and strengthened armature winding (4), a lacquered wire with a baked lacquer coating is used as the winding wire, which coating is so softened by temperature effect that, after the winding has cooled, a firm bond is provided at the mutual contact points of the wires. For the baked lacquer coating, synthetic resins on a polyamide basis (thermoplastics), or on a polyester or epoxy basis (duroplastics) are preferred. As a result, the impregnation of the armature winding (4) may remain stable even under the action of fuel and no longer tends to break away. <IMAGE>

Description

SPECIFICATION Improvements in or relating to fuel supply units The present invention relates to fuel supply units, and has particular reference to a method of making a fuel impermeable armature winding for an electrically driven fuel supply unit and also to a unit incorporating a winding of that kind.

It is known that the armature or armature components of an electric motor, especially one that is arranged as a combined unit together with the pump component driven by the motor to form a fuel supply unit, may be impregnated with a synthetic resin, in order to achieve mechanical strengthening in the region of the windings.

In the conventional production of armatures for electric motors, especially for electric fuel pumps, the laminated core on a shaft or support tube is first of all injection coated with plastics, both for the purpose of stabilizing it on this shaft and for achieving an insulation with respect to the winding wire.

The winding is then mounted on the armature and impregnated with a synthetic resin, in order to provide mechanical strengthening. This impregnation with synthetic resin is followed by a comparatively long drying and hardening phase.

Finally, it is necessary to balance an armature made in this way, due to the non-uniform way in which the resin masses become distributed. These operations are comparatively costly and some of them involve subsequent operations for example removal from the periphery of the laminated core of injection skins which arise in the injection operation and give rise to a risk of pump failure if they break.

A further drawback is that resin break-aways occur at the winding components and/or at the insulation of the armature under the action of fuel, sometimes even only of specific fuel components and as a consequence of a possibly increased temperature, so that for this reason interruption of the operation of an electric fuel pump can occur.

The impregnating or coating of the armature with synthetic resin is usually carried out by a dip impregnation using suitable phenoiic resins.

A further disadvantage is that, as a consequence of the necessary temperature loading (the drying and hardening phase of the synthetic resin), the plastics component, usually present on the armature, for coupling to the rotational component of an associated fuel pump can suffer a loss of strength.

There therefore exists a need for a more rotational manufacturing method for armatures for electric motors, especially in fuel supply units, by which the mechanical attachment of the armature winding can be simplified and made fuel-resistant, and which in particular may be free of faults and offer advantages in the dynamic field.

According to a first aspect of the present invention there is provided a method of making a fuel-impermeable armature winding for an electrically driven fuel supply unit, comprising the steps of forming the winding from a wire having a baked lacquer coating with a synthetic resin base, and so softening the coating by the application of heat thereto as to cause, on subsequent cooling of the coating, the portions of the coating on contiguous sections of the wire to fuse together.

According to a second aspect of the present invention there is provided an electrically driven fuel supply unit comprising an electric motor with a synthetic resin impregnated armature winding formed from a wire having a baked lacquer coating in which the portions of the coating on contiguous sections of the wire are fused together through heating.

A method according to an example, and a fuel supply unit according to an embodiment, of the invention may possess the advantages that resin breakaways at windings and/or core insulation, and also adverse effects on the driving journal of the driving coupling for the pump rotational component, are avoided. In addition, the armature can be made more rapidly, without long drying and hardening times, and thus more rationally.

interruption of the operation of the electrical fuel supply unit may also be avoided, since while on the one hand the windings of the armature firmly bond to one another, on the other hand resin break-aways virtually cannot occur, because the resin is present only in the form of the baked lacquer coating on the winding wire and is not present in larger quantities which could peel off.

Accordingly, a method exemplifying the invention for the strengthening of armature winding layers may be more rational and more favourable to the environment than the known dipped impregnation with phenolic resin. Finally, due to the omission of the temperature loading on the plastics driving journal on the armature during the drying of the dip lacquer, a loss of strength of the driving journal is avoided.

Advantageously, the resin of the baked lacquer coating is a polyamide (thermoplastics), polyester or epoxy (duroplastic).

An example and an embodiment of the invention will now be more particularly described with reference to the accompanying drawing, which is a partially sectioned side view of an armature for an electric fuel pump, comprising an armature laminated core and winding, the armature winding being illustrated in a highly diagrammatic form. For reasons of simplifying the drawing, the lacquered wires of the winding with a baked lacquer coating have not been individually illustrated.

Referring now to the drawing there is shown an electric motor which, in combination with a pump component, forms a composite unit for the supply of fuel. As will be explained in more detail, the motor has an armature winding with a baked lacquer coating in which, after a temperature action has been applied to it, a baking-together of the coating material and thus strengthening of the winding is obtained.

In the drawing the armature is referenced 1 and comprises a central stationary shaft or axle 2, a laminated core 3, a winding 4 and a commutator 5, the individual segments of which are electrically connected to specific regions of the winding, as shown at 6. In the illustrated embodiment, the rotatable part of the armature is journalled by means of a hollow shaft 7 with bearings 8 and 9 at both ends on the axle 2, which can be secured in any desired manner within the housing of an electric fuel pump. The drive of the pump component (not shown) is, in the present embodiment, effected by means of a plastics coupling assembly 10, consisting of entraining fingers 1 Oa and 1 Ob disposed on the end of the armature remote from the commutator, which fingers engage with the rotating part of the pump.

In the usual arrangement, the electric motor is situated together with the pump component driven by it (most frequently a side channel pump (regenerative pump) or roller cell pump) in a common housing, so that the region of the electric motor is traversed by the supplied fuel, which may perhaps be only under vacuum, and the armature revolves in the fuel. Thus extremly intimate contact occurs under the action of forces between the entire armature region and the fuel, possibly at high tempertures. In the example and embodiment of the invention, however, a mechanically firm and fuel-resistant impregnation of the armature winding is achieved, due to the fact that this winding as a whole and preferably in all its layers consists of a lacquered wire with a baked lacquer coating.Such a coated, electrically conducting wire consists of an electrically conducting metal portion, usually of copper, which constitutes the core, and an insulation surrounding this copper core, at least the outer encasing layers of which contain synthetic resin constituents, preferably on a polyamide basis, a polyester or an epoxy basis. The wire as a whole is designated as a lacquered wire with a so-called baked lacquer coating, which then softens under temperature effect of the armature or armature winding, so that after the winding has cooled a firm adhesive bond is obtained at the individual points of contact of the wires.

This adhesive bond is a form of welding together of the baked lacquer coating, softened the partially liquefied by the temperature effect on the wire, the coating being thermoplastic when it is based upon a polyamide or duroplastic when it has a polyester of epoxy base.

The baking together of the armature winding, that is overall the solidifying and compaction of the armature winding to a consistent, rigid entity which cannot be dislocated, is carired out by introducing the armature into a hot cabinet for a predetermined period, by subjecting it in some other way to thermal radiation or the action of hot air, or by introducing into the armature winding a suitably designed current surge. Such a current surge results in heating of all the windings to the same extent, a heating which results in the softening of the outer coating of baked lacquer and thus in the baking together and welding together at the mutual points of contact of the wires.

The example and embodiment of the invention ensure that the fuel-resistant impregnation of the invention of the armature of the electric fuel pump is present at all points of the armature, including those which are not reached by the synthetic resin in a simple dip process. Since the winding itself is the carrier for the impregnation, a completely uniform and consistent bond and strengthening of the individual winding components is assured.

Claims (11)

1. A A method of making a fuel-impermeable armature winding for an electrically driven fuel supply unit, comprising the steps of forming the winding from a wire having a baked lacquer coating with a synthetic resin base, and so softening the coating by the application of heat thereto as to cause, on subsequent cooling of the coating, the portions of the coating on contiguous sections of the wire to fuse together.
2. 2. A method as claimed in claim 1 , wherein the synthetic resin base is one of polyamide, polyester and epoxy.
3. 3. A method as claimed in either claim 1 or claim 2, wherein the step of applying heat to the coating comprises placing the winding in an enclosed space having an elevated temperature.
4. 4. A method as claimed in either claim 1 or claim 2, wherein the step of applying heat to the coating comprises supplying a surge of electrical current to the winding.
5. 5. A method of making a fuel-impermeable armature winding for an electric fuel supply unit, the method being substantially as hereinbefore described with reference to the accompanying drawing.
6. 6. A fuel impermeable armature winding, for an electrically driven fuel supply unit and when made by a method as claimed in any one of the preceding claims.
7. 7. An electrically driven fuel supply unit comprising an electric motor with a synthetic resin impregnated armature winding formed from a wire having a baked lacquer coating in which the portions of the coating on contiguous sections of the wire are fused together through heating.
8. 8. A fuel supply unit as claimed in claim 7, further comprising a pump component and a housing containing both the motor and the pump component.
9. 9. A fuel supply unit as claimed in either claim 7 or claim 8, wherein the coating has a synthetic resin base.
10. 10. A fuel supply unit as claimed in claim 9, wherein the synthetic resin of the coating is one of polyamide, polyester and epoxy.
11. 11. A fuel supply unit substantially as hereinbefore described with reference to the accompanying drawing.