EP3084781B1 - Electric solenoid and use of an electric solenoid - Google Patents

Description

State of the art

The invention relates to an electric coil according to the preamble of claim 1. Furthermore, the invention relates to the use of an electric coil according to the invention.

An electric coil according to the preamble of claim 1 is already known as part of a fuel injector for injecting fuel into the combustion chamber of an internal combustion engine from practice. In particular, the electric coil serves to actuate an injection member, for example in the form of a nozzle needle, indirectly or directly in order to close or release injection openings formed in the fuel injector.

Conventional electric coils have a plastic bobbin on which a large number of turns of a coil wire is wound. The coil wire usually consists of a wire core made of copper, which is surrounded by an insulator layer, for example, baked enamel. Although the use of copper as a wire core has the advantage of a relatively low resistivity, but this resistance is temperature-dependent, such that with increasing temperature and the resistance of the copper wire increases. This has the consequence that in an operation, for example, a fuel injector, which is used in a cylinder head of an internal combustion engine, the temperature of the fuel injector and thus the temperature of the electric coil increases, resulting in an increased electrical resistance of the coil wire. This results in a decreasing magnetic force with increasing temperature, so that the proper functioning of, for example, an injection member at high temperatures can be critical. For this reason, it is common to have the packing or power density of such Increase electric coils. This is done for example by a profile wire with which it is possible to increase the degree of filling of the wire windings on a bobbin.

From the DE 10 2008 034 408 A1 For example, a coil having a coil core and a coil wire is known, wherein the core wire is made of aluminum. Out US 2013/020877 A1 For example, a wire is known in which the graphene is applied to the surface of the wire core. The CN 103 021 502 A discloses a wire having a wire core of copper clad aluminum with graphene deposited on the copper. Out S. Bartolucci et al .: "Graphene-aluminum nanocomposites", Materials Science and Engineering A 528 (2011) 7933-7937 , In addition, a composite material of aluminum and graphene is known.

Since the tendency of future injection systems is more and more to high system pressures and thus higher required actuation forces for an injection member, future requirements without increasing the size of an electric coil are increasingly difficult to meet with conventional electric coils according to the prior art.

Disclosure of the invention

Based on the illustrated prior art, the invention has the object, an electric coil according to the preamble of claim 1 such that the strong temperature-dependent in the prior art resistance characteristic of the electric coil is reduced. In addition, the highest possible power density, ie the highest possible magnetic actuation force can be achieved with a certain size of a bobbin. This object is achieved in an electric coil with the features of claim 1, characterized in that the wire core of the coil wire made of aluminum and arranged with the aluminum in electrically conductive contact graphene. Such a material mix has the advantage that it has a combination of the known relatively low change in resistance over the temperature profile and an overall relatively low resistivity, similar to the use of copper.

Advantageous developments of the electric coil according to the invention are listed in the subclaims. All combinations of at least two of the features disclosed in the claims, the description and / or the figures fall within the scope of the invention.

In order to realize the mentioned material combination according to the invention, it is provided in a first embodiment of the invention that the graphene is at least substantially homogeneous in cross section of the wire core in the Distributed aluminum and arranged oriented in the power line direction. For this purpose, it should be noted that graphene is usually formed in the form of platelets, ie a very thin cross-section having elements, so that it is essential that the orientation of the graph in the power line direction takes place. In this case, it may be possible for the individual graphene elements to be spatially separated from one another in the direction of the current line, or, particularly advantageously, to be overlapping one another so that a continuous conductive graphene layer is achieved in the current line direction. In the event that the individual graphene elements are separated from one another in the direction of current conduction, an electrical conduction takes place between the graphene elements through the aluminum arranged in electrically conductive contact with the graphene. Therefore, it is also important or essential that at least substantially no, the power line reducing effects, such as air inclusions or the like, are present within the cross section.

In an alternative embodiment of the invention, it is also possible for the graphene to be formed as a layer which is separate from the aluminum and electrically conductively connected to the aluminum, preferably in the direction of flow, preferably on a surface of the wire core. In such an embodiment, it is considered advantageous that the two components serving the power line, the aluminum and the graphene, may optionally be formed in separate manufacturing processes or manufacturing steps, which are subsequently connected to one another in an electrically conductive manner. Alternatively, it is also possible to arrange or deposit the graphene on an already existing aluminum layer or an aluminum carrier. Thus, the aluminum serves as a carrier material for arranging or training of graphene.

In the prior art, the commonly used insulating layers of plastic (eg baked enamel) with the use of copper wires to a thickness of about 50 .mu.m. Since the insulating layer does not serve the power line, a decreasing packing density or performance of the electric coil results with an increasing thickness of the insulating layer. For this reason, it is particularly preferred according to the invention for the insulating layer to comprise an aluminum oxide layer having a thickness of between 1 μm and 10 μm, preferably between 2μm and 5μm. An oxide layer has the advantage over the use of plastic in particular that it has a high thermal conductivity and thus also allows a relatively effective dissipation of the heat of the coil wire. In addition, the performance of the electric coil is increased by an increased filling factor by the particularly thin design of the insulating layer compared to an insulating layer made of plastic. The coating or training with alumina is carried out in particular by anodic oxidation (Eloxal method). Anodic oxidation is an electrolytic process that produces an oxide layer on a surface that is approximately 100 times stronger than a naturally formed (oxide) layer so that, in practice, a 4 μm thick insulating layer will suffice if the voltage breakdown strength is adequate.

A particular embodiment of the insulating layer provides that the insulating layer only partially covers the graphene. This is particularly provided when aluminum strips are used in which the graphene is applied to one side as a coating. Since the graphene is used for the power line and has a very low electrical resistance, it is essential here that, when the coil wire is wound over one insulating layer in each case, it covers the underlying, partially exposed graphene layer.

In addition, a geometrical configuration of the coil wire, in which the latter has at least essentially a rectangular cross section, is very particularly preferred. Such a design increases the fill factor and thus the power density of the electric coil to a particularly high degree and therefore allows for a certain performance particularly small or compact electrical coils.

In order to be able to wind a bobbin over its entire axial length with such a coil wire having a rectangular cross-section in order to enable the highest possible power density or the highest possible fill factor, it is furthermore provided in a preferred embodiment that the coil wire has a width has, which corresponds to the width of the bobbin in the longitudinal direction thereof.

However, the same effect can alternatively be achieved by having the coil wire having a width equal to 1 / n times the width of the bobbin in its longitudinal direction, and two coil wires connected to each other in the longitudinal direction of the bobbin being electrically conductively connected to each other.

The mentioned advantageous effects of the electric coil according to the invention are always particularly effective if the electric coil are at least temporarily exposed to different temperatures, at temperatures of more than 150 ° C, in particular more than 200 ° C, the advantages over conventional electric coils are particularly large ,

Such an electric coil according to the invention is therefore used, in particular, as a component of a motor vehicle injection component, in particular a fuel injector, in which the fuel injector or its electric coil is exposed to relatively low temperatures, for example during a cold start, and, on the other hand, during operation to the high temperatures of up to can reach over 200 ° C. In principle, the electric coil according to the invention can be used in all applications in which a particularly high performance and / or a small installation space for the electric coil is desired.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing.

Fig. 1

einen Längsschnitt durch eine Elektrospule, bei der in Längsrichtung betrachtet zwei Spulendrahteinheiten nebeneinander angeordnet sind,

Fig. 2

eine perspektivische Darstellung eines in Form einer Rolle ausgebildeten Spulendrahtelements,

Fig. 3

einen Querschnitt durch ein erstes erfindungsgemäßes Spulendrahtelement

Fig. 4

einen Querschnitt durch ein gegenüber Fig. 3 modifiziertes Spulendrahtelement und

Fig. 5

eine Darstellung des Widerstandsverlaufs unterschiedlicher Materialien über der Temperatur.

This shows in:

Fig. 1

a longitudinal section through an electric coil, in which viewed in the longitudinal direction two coil wire units are arranged side by side,

Fig. 2

a perspective view of a formed in the form of a coil wire element,

Fig. 3

a cross section through a first inventive coil wire element

Fig. 4

a cross section through one opposite Fig. 3 modified coil wire element and

Fig. 5

a representation of the resistance profile of different materials over the temperature.

The same elements or elements with the same function are provided in the figures with the same reference numerals.

In the Fig. 1 an electric coil 10 according to the invention is shown, as used for example as part of a motor vehicle injection component in the form of a fuel injector. In particular, the electric coil 10 serves for the at least indirect actuation of an injection valve member (nozzle needle) into the fuel injector.

The electric coil 10 comprises a coil made of plastic, injection-molded coil body 11 in the form of a sleeve with two laterally arranged, the bobbin 11 longitudinally delimiting, radially circumferential flanges 12, 13 and a concentric with the longitudinal axis 14 of the bobbin 11 arranged in this recess 15th Between the two flanges 12, 13, the bobbin 11 forms an in particular circular peripheral surface 16 for the arrangement of at least one coil wire unit 20. In the illustrated embodiment, viewed in the axial direction of the longitudinal axis 14, two coil wire units 20 are provided on the bobbin 11, which are electrically connected to each other (not shown) by a wire end of a coil wire unit 20 is connected to a wire end of the other coil wire unit 20. In particular, the width b of the two identically designed coil wire units 20 is approximately half the width B of the bobbin 11 between the two flanges 12, 13, so that the space between the two flanges 12, 13 is at least almost completely filled.

As with a synopsis of Fig. 2 to 4 is recognizable, consists of the coil wire 25, 25 a of the coil wire unit 20, which is wound in the form of a plurality of turns on the bobbin 11, made of two different materials, of aluminum 21 and graphene 22. In the embodiment according to the Fig. 3 consists of the coil wire 25 with a wire core 23, consisting of aluminum 21. In power line direction, ie perpendicular to the plane of the Fig. 3 , 21 platelets of graphene 22 are arranged in the aluminum, the platelets perpendicular to the plane of the drawing Fig. 3 either all of them are electrically connected directly to one another in the form of a strip, or else they are arranged at intervals with respect to one another. In particular, the distribution of the graphene 22 within the wire core 23 or the aluminum 21 is at least substantially homogeneous.

The coil wire 25 having a rectangular cross-section of the width b is surrounded by an insulation layer 26, which in particular has a uniform wall thickness a, over the entire cross-section of the coil wire 25. The insulating layer 26 is formed as an aluminum oxide layer 27 and produced, for example, in the anodizing process. In particular, the wall thickness a of the insulating layer 26 is between 1 μm and 10 μm, preferably between 2 μm and 5 μm, very particularly preferably 4 μm. Such a manufactured coil wire 25 can be according to the illustration of Fig. 2 store in the form of a wound-up belt 28 or process it by machine.

In the Fig. 4 is opposite Fig. 3 modified coil wire 25a shown. The wire core 23 of the coil wire 25a is made of aluminum 21 without graphene 22. The graphene 22 is applied as a band-shaped layer on the surface or on the upper side 29 of the wire core 23 and electrically conductively connected thereto. The insulating layer 26 also consists of an aluminum oxide layer 27, which completely surrounds the wire core 23 in the area outside of the graphene 22. In the region of the graphene 22, the insulation layer 26 extends laterally as far as the graphene 22, but the graphene 22 is not surrounded or covered by the insulation layer 26 on the upper side facing away from the wire core 23.

When winding the bobbin 11 by means of the coil wire 25a, it is essential that a plurality of layers of the coil wire 25a are stacked one above the other can be arranged or wound, that on the graph 22 of a radially lower layer each an insulating layer 26 of a winding arranged above is wound.

In the Fig. 5 is shown over the temperature T (x-axis) the resistivity R _S (Y-axis) of different materials. The reference numeral 31 shows the course of the resistivity R _S of aluminum, while the reference numeral 32 illustrates the course of the resistivity R _S of copper. Reference numeral 33 represents the specific resistance R _{S of} the material combination according to the invention, consisting of aluminum 21 and graphene 22. It can be seen that, with increasing temperature, such a combination of materials has a virtually constant or merely slightly increasing specific resistance R _S , which, with regard to its absolute value, is of the order of magnitude of copper at relatively low temperatures.

The electric coil 10 according to the invention can be modified or modified in many ways, without departing from the spirit of the invention. It is conceivable, for example, instead of a substantially rectangular cross-section for the coil wire 25, 25a to form this cross-section square or, in the case of the graphite 22 arranged in the aluminum 21, roundly. It should also be noted that the use of the invention should not be limited to electric coils 10, which serve as part of a fuel injection component.

Claims (10)

1. Electric solenoid (10), comprising at least one solenoid body (11) and a coil wire (25; 25a) surrounding the solenoid body (11) on a peripheral surface (16) of the solenoid body (11) in the form of at least one winding, wherein the coil wire (25; 25a) consists of an electrically conductive wire core (23) and an insulating layer (26) surrounding the wire core (23) at least in regions,
   wherein
   the wire core (23) contains aluminum (21), characterized in that the wire core (23) has graphene (22) arranged in electrically conductive contact with the aluminum (21).
2. Electric solenoid according to Claim 1, characterized in that
   the graphene (22) is distributed in the aluminum (21) at least substantially homogenously in the cross section of the wire core (23) and is oriented in the current conduction direction.
3. Electric solenoid according to Claim 1, characterized in that
   the graphene (22) is formed as a layer, which is separate from the aluminum (21), is electrically conductively connected to the aluminum (21), and is preferably continuous in the current direction, preferably on an upper side (29) of the wire core (23).
4. Electric solenoid according to one of Claims 1 to 3,
   characterized in that
   the insulation layer (26) is an aluminum oxide layer (27) having a thickness (a) between 1 µm and 10 µm, preferably between 2 µm and 5 µm.
5. Electric solenoid according to Claim 3 or 4,
   characterized in that
   the insulation layer (26) covers the graphene (22) only in part.
6. Electric solenoid according to one of Claims 1 to 5,
   characterized in that
   the coil wire (25; 25a) has an at least substantially rectangular cross section.
7. Electric solenoid according to Claim 6,
   characterized in that
   the coil wire (25; 25a) has a width (b) corresponding at least substantially to the axial width (B) of' the solenoid body (11) in the longitudinal direction thereof.
8. Electric solenoid according to Claim 6,
   characterized in that
   the coil wire (25; 25a) has a width (b) corresponding at least substantially to 1/n times the width (B) of the solenoid body (11) in the longitudinal direction thereof, and in that two coil wires (25; 25a) adjacent to one another in the longitudinal direction of the solenoid body (11) are electrically conductively connected to one another.
9. Use of an electric solenoid (10) according to one of Claims 1 to 9, in which the electric solenoid (10) is exposed to a temperature of more than 150°C, in particular more than 200°C.
10. Use of an electric solenoid (10) according to Claim 9 as part of a motor vehicle injection component, in particular a fuel injector.

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