FR3059142A1 - ELECTROMAGNETIC ACTUATING DEVICE - Google Patents

Abstract

Electromagnetic actuating device (2) having a fixed part and a movable part, the fixed part including among others a coil (10) consisting of a wire (12) of electrically conductive material, the coil (10) having a number of turns of wire (12) determined characterized in that the wire (12) is composed of at least a first electrically conductive material (M1) having a circular section and is covered with a second electrically conductive material (M2) with a section annular, both being concentric.

Description

Holder (s): CONTINENTAL AUTOMOTIVE FRANCE Simplified joint-stock company, CONTINENTAL AUTOMOTIVE GMBH.

Extension request (s)

Agent (s): CONTINENTAL AUTOMOTIVE FRANCE.

ELECTROMAGNETIC ACTUATION DEVICE.

FR 3 059 142 - A1 (57) Electromagnetic actuation device (2) comprising a fixed part and a mobile part, the fixed part having inter alia a coil (10) consisting of a wire (12) made of electrically conductive material, the coil (10) having a determined number of turns of wire (12) characterized in that the wire (12) is composed of at least one first electrically conductive material (M1) having a circular section and is covered with a second electrically conductive material (M2) with an annular section, both of which are concentric.

The present invention relates generally to an electromagnetic actuation device and relates more particularly to the design of an electromagnetic actuator.

The invention finds applications, in particular, in the automotive industry. It can be implemented, for example, in an anti-lock braking system, from the English acronym "Anti Blocking System" or ABS brakes.

A motor vehicle is embedding more and more electronic functions to improve its use but also to reduce its fuel consumption. Thus, nowadays a motor vehicle comprises several electronic computers to manage for example, engine control functions, air conditioning functions but also functions related to braking. Thanks to electronics, certain functions previously performed by assemblies of relatively complex mechanical parts are now partially or totally replaced by electrically controlled devices.

We can cite for example, the activation of the valves of an internal combustion engine which, before was carried out by a camshaft, itself in dynamic collaboration with a crankshaft, and which now is more and more often carried out by electromagnetic actuators. Generally, these electromagnetic actuators are solenoid valves electrically controlled by an electronic computer.

An electromagnetic actuator transforms electrical energy into mechanical energy. Thus, a current, which flows in electrical conductors generally located on a fixed part of the electromagnetic actuator forms a magnetic field which interacts with a magnetic field produced by a second magnetic source generally located on a mobile part. The second magnetic source can be created either by permanent magnets or by coils.

The coils are generally made of a very good electrically conductive material such as copper. The mechanical power or the tensile force developed during the passage of current through the coil is mainly linked to three technical factors: the number of turns of the coil, the diameter of the wire and the material used. Of course, those skilled in the art will understand that the assumptions made to achieve the dimensioning of the coil have been simplified to facilitate understanding of the invention and its technical problem.

Copper is a very good electrical conductive ductile material with an electrical conductivity of 59.6x10 ^e Sm ¹ (pure copper) which makes it the most used metal for electrical applications. However, copper has a density of about 8.96 g-cm ³ (at 20 ° C) which also makes it a heavy material.

With the increase in the number of electromagnetic actuators in a motor vehicle, these begin to play a significant part in the increase in the total mass of the motor vehicle.

The invention proposes an electromagnetic actuator making it possible to partially or totally remedy the technical shortcoming of the cited prior art.

To this end, a first aspect of the invention proposes an electromagnetic actuation device comprising a fixed part and a movable part, the fixed part having inter alia a winding made up of a wire of electrically conductive material, the winding having a number of determined turns, characterized in that the wire is composed of at least a first electrically conductive material having a circular section and is covered with a second electrically conductive material with an annular section, both of which are concentric.

Thus, thanks to the invention it is possible to reduce the mass of the electromagnetic actuator.

For example, it is proposed that the first electrical conductive material has a first electrical conductivity lower than a second electrical conductivity of the second electrical conductive material.

To reduce the mass of the electromagnetic actuation device, it is for example proposed that the first electrically conductive material has a first density density of mass less than a second density density of mass of the second electrically conductive material.

To obtain a significant reduction in the total mass of the coil, it is for example proposed in an alternative embodiment of the invention that the first electrically conductive material represents at least 50% of a total section of the winding wire.

In order to be able to obtain compatibility with the other electronic components on board the motor vehicle, the first electrically conductive material is for example aluminum.

To ensure performances similar to the coils of the prior art, it is advantageously proposed, for example that the second electrically conductive material is copper.

Details and advantages of the present invention will appear more clearly in the description which follows, given with reference to the appended schematic drawing in which:

- Figure 1 is a sectional view of an electromagnetic actuator,

FIG. 2 represents a comparison of the performances of a coil of the prior art compared to a coil according to the present invention, and

- Figure 3 is a sectional view of a coil wire according to the present invention.

In Figure 1 is shown an electromagnetic actuator 2 comprising a body 4 which defines a central axis A-A ’. In the following description, the central axis A-A 'is fixed and constitutes a central axis for all the elements of the electromagnetic actuator 2. In an exemplary embodiment, the body 4 has a tubular shape and has two bases 4A and 4B axially opposite. In each of these bases 4A and 4B is provided a bore. In Figure 1 (sectional view) the bore is split into two parts with a first bore part 6A and a second bore part 6B. The first part of bore 6A and the second part of bore 6B make it possible to create an internal volume 8.

A coil 10 is arranged in the internal volume 8. For example, the coil 10 is integral with the body 4. The coil 10 is composed of a wire 12 having a determined diameter and a determined length. The coil 10 is adapted to be coupled, in a known manner to an electrical circuit which is not shown in FIG. 1.

The electromagnetic actuator 2 also comprises a sheath 14 having a hollow cylindrical shape with for example a solid wall. The sheath 14 is disposed against the coil 10 along the central axis A-A ’. For example, the sheath 14 is made of metal.

The electromagnetic actuator 2 further comprises a magnetic core 16 of cylindrical shape arranged in the sheath 14. The magnetic core 16 is movable in translation along the central axis A-A ’as a function of a current flowing in the coil 10.

In order not to burden the description, the internal structure of the electromagnetic actuator 2 in FIG. 1 has been deliberately simplified. The electromagnetic actuator 2 can be, for example an electromagnetic actuator dedicated to the braking assistance of a motor vehicle. This example is purely illustrative and is by no means restrictive. In fact, the electromagnetic actuator 2 can also be an electromagnetic actuator for controlling the valves of a variable valve injection system.

As mentioned above in the description, the electromagnetic actuator 2 is dimensioned so as to be able, as a function of a determined current, to move an object such as for example the magnetic core 16 over a determined distance. It can also be dimensioned to counteract a force, for example that of a spring fixed to the magnetic core 16. Thus, as is known to those skilled in the art, the mechanical power or the tensile force developed by the electromagnetic actuator 2 mainly depends on the dimensioning of the coil 10. Indeed, this mechanical power depends on the magnetic field created during the passage of current through the coil 10; therefore, this depends mainly on the number of turns of the wire 12 of the coil 10, the diameter of the wire 12 and also the material of the wire 12.

In the case, for example, of an electromagnetic actuator 2 dedicated to ABS type braking assistance, the following specifications may be requested:

- range of attraction force: 2 N - 9 N;

- operating current range: 0.25 A -1.75 A;

- size: 1.5 cm ³ .

In order to meet these specifications, electromagnetic actuators 2 of the prior art have coils 10 with the following characteristics:

- wire material 12: 99.9% pure copper;

- wire diameter 12: 0.230 mm;

- number of turns: 365.

These technical characteristics are given for illustrative purposes only.

Graph 1 in FIG. 2 illustrates the attraction capacity of an electromagnetic actuator 2 of the prior art with the characteristics of the coil 10 presented above. Thus, it is possible with an applied current between 0.25 A and 1.75 A to release an attraction force between 2 N and 9 N.

Such an electromagnetic actuator of the prior art also has a mass of the order of 50 g, 30% to 60% of which comes from the coil 10 and therefore from its wire 12.

Knowing that there are more and more electromagnetic actuators 2 in a motor vehicle, the impact of these on the total mass of the motor vehicle is now not negligible. Indeed, it is not uncommon for a motor vehicle today to carry around a hundred electromagnetic actuators 2.

In addition to the mass issue of the electromagnetic actuator 2, there is also a concept of cost. Indeed, the use of copper to make the coil 10 of the electromagnetic actuator 2 generates an additional cost which, too, is not negligible.

To reduce the mass of the electromagnetic actuator 2, the present invention proposes to use a new wire technology 12 to produce the coil 10. To do this and as illustrated in FIG. 3, it is proposed to use a wire 12 composed of at least two different electrically conductive materials. For example, the wire 12 can be composed of a first electrical conductive material M1 having a circular section S1 and a second electrical conductive material M2 covering the first electrical conductive material M1. Thus, the second electrically conductive material M2 has an annular section S2. Advantageously, the circular section S1 and the annular section S2 are concentric.

In order to reduce the mass of the coil 10 and therefore reduce the mass of the electromagnetic actuator 2, the first electrically conductive material M1 has a first density density of mass p1 lower than that of copper. Thus, for example, the first electrically conductive material M1 is composed of aluminum having a first density density of mass p1 of the order of 2.7 g-cm ³ (20 C).

Advantageously, in order to preserve the performance of a coil 10 of the prior art with a copper wire 12 (solid), it is proposed in a preferred embodiment that the second electrically conductive material M2 is copper. Thus, the performance of the coil 10 with a bi-material wire 12 is substantially identical to that of a coil 10 of the prior art.

In order to significantly reduce the mass of the electromagnetic actuator 2, but with performances substantially identical to those of an electromagnetic actuator 2 of the prior art, it is in an exemplary embodiment proposed that the first electrically conductive material M1 represents at least 50% of the surface of the total cross section of the wire 12. In FIG. 3, the first electrically conductive material M1 presents approximately 75% of the surface of the total cross section of the wire 12 which advantageously makes it possible to reduce the total mass of the coil 10 significantly with respect to a coil 10 of an electromagnetic actuator 2 of the prior art.

In the example illustrated in FIG. 3, the mass of the copper represents only 15% of the total mass of the wire 12. Thus, the coil 10 has a lesser mass compared to the mass of a coil 10 of the art prior.

In graph 2 of FIG. 2, the electrical performance of the wire 12 illustrated in FIG. 3 is presented, that is to say a wire 12 consisting of a first electrically conductive material M1 having approximately 75% of the surface cutting the wire 12 and a second electrically conductive material M2; the first electrically conductive material M1 is aluminum and the second electrically conductive material M2 is copper.

As shown in FIG. 2, for equivalent performance, the diameter of the wire 12 made of bi-materials according to the present invention is appreciably smaller than that of a coil 10 of the prior art and has a value for example of 0.200 mm.

Thus, to meet the specifications presented above, the coil 10 with a wire 12 using a bi-material technology has the following characteristics:

- wire material 12: aluminum / copper with a 15% / 85% ratio;

- wire diameter 12: 0.200mm;

- number of turns: 400.

Advantageously, it is thus possible to produce an electromagnetic actuator 2 with, for example, a pulling force of 2N for a current applied to the coil 10 of 0.25A and a pulling force of 9N for a current applied of 1.75A, with a total mass reduced by at least 30% compared to an electromagnetic actuator 2 of the prior art. In addition, such an electromagnetic actuator 2 according to the present invention will have a manufacturing cost which is substantially lower than the manufacturing cost of an electromagnetic actuator of the prior art.

Of course, the digital examples cited above are given purely by way of illustration and do not limit the scope of the invention.

Alternatively, it is also possible to use a coil composed of at least three wires of electrically conductive materials, with a layer sequence which can be aluminum, gold, copper improving the conductivity and therefore the force of attraction with a total mass. even lower.

Of course, the present invention is not limited to the preferred embodiment described above and illustrated in the drawing and to the variant embodiments mentioned, but extends to all variants within the reach of the skilled person.

Claims (6)

1. Electromagnetic actuation device (2) comprising a fixed part and a movable part, the fixed part having inter alia a coil (10) consisting of a wire (12) made of electrically conductive material, the coil (10) having a number of turns of wire (12) determined characterized in that the wire (12) is composed of at least a first electrically conductive material (M1) having a circular section and is covered with a second electrically conductive material (M2) with an annular section, both being concentric. 2. An electromagnetic actuation device (2), according to claim 1 characterized in that the first electrical conductive material (M1) has a first electrical conductivity (γ1) lower than a second electrical conductivity (γ2) of the second electrical conductive material ( M2). 3. electromagnetic actuation device (2) according to any one of claims 1 or 2 characterized in that the first electrically conductive material (M1) has a first density density of mass (p1) less than a second density density of mass (p2) of the second electrically conductive material (M2). 4. An electromagnetic actuation device (2) according to any one of claims 1 to 3 characterized in that the first electrically conductive material (M1) represents at least 50% of a total section of the wire (12) of the coil (10). 5. An electromagnetic actuation device (12) according to any one of claims 1 to 4 characterized in that the first electrically conductive material (M1) is aluminum. 6. Electromagnetic actuation device (2) according to any one of claims 1 to 5 characterized in that the second electrically conductive material (M2) is copper. 1/3