CN117741771A - Steering wheel off-hand sensor, steering wheel and related area arrangement method - Google Patents

Abstract

The application provides a steering wheel release sensor, a steering wheel and a related area arrangement method, which are applied to the technical field of automobile parts and comprise an induction layer, an insulating layer and a shielding layer; an insulating layer separates the sensing layer from the shielding layer, the sensing layer comprising at least one sensing region, the shielding layer comprising a conductive fabric formed of at least nickel coated polyester fibers or polyester amine threads; the shielding layer is configured in plurality, and at least one sensing area is configured to correspond to at least two shielding layers. The shielding layer is a conductive fabric formed by at least nickel-coated polyester fibers or polyester amine wires, at least one sensing area corresponds to at least two shielding layers, the probability of insufficient coverage of the shielding layers caused by a complex structure of the steering wheel can be reduced, and meanwhile the probability of short circuit between the shielding layers at the edge caused by pulling of leather on the sensing layers can be reduced.

Description

Steering wheel off-hand sensor, steering wheel and related area arrangement method

Technical Field

The application relates to the technical field of automobile parts, in particular to a steering wheel release sensing sensor, a steering wheel and a related area arrangement method.

Background

In order to effectively improve driving safety, it is a safety regulation requirement that the state recognition of the hand-held steering wheel requires that the hand cannot be separated from the steering wheel, and the system should be able to determine whether the hand of the user holds the steering wheel according to the surface of the steering wheel or built-in sensors. It is therefore important to accurately detect whether the steering wheel is in an hands-off state. Currently, capacitive sensors are typically deployed on the surface of the steering wheel to identify whether the user's hand is holding the steering wheel. The resistive stability of the shielding and metal layers of the capacitive sensor is critical to the system function. Wherein, the range that the sensing layer of car steering wheel from hand sensor exceeded current shielding layer can lead to a series of signal problems that go away the hand and detect, and the signal can be disturbed easily, leads to the performance unstable.

Based on this, a new solution is needed.

Disclosure of Invention

In view of this, the embodiments of the present disclosure provide a steering wheel off-hand sensor, a steering wheel, and a related area arrangement method.

The embodiment of the specification provides the following technical scheme:

the embodiment of the specification provides a steering wheel separation hand sensor, which comprises a sensing layer, an insulating layer and a shielding layer; the insulating layer separates the sensing layer and the shielding layer, the sensing layer comprises at least one sensing area, and the shielding layer comprises conductive fabric formed by at least nickel-coated polyester fiber or polyester amine wire;

the shielding layer is configured in a plurality, and at least one sensing area is configured to correspond to at least two shielding layers.

Preferably, the plurality of shielding layers includes a first shielding layer and a second shielding layer;

the first shielding layer is arranged in the insulating layer, the second shielding layer is arranged on the surface of the insulating layer, and the projection of the first shielding layer and the second shielding layer in the direction perpendicular to the insulating layer completely covers the sensing area.

Preferably, the first shielding layer is annular and covers the outer edge area of the insulating layer, and the second shielding layer is sheet-shaped and covers the central area of the insulating layer.

Preferably, the first shielding layer is connected with the second shielding layer through a wire;

alternatively, the first shielding layer is grounded through a wire.

Preferably, the first shielding layer is embedded in the edge part of the insulating layer, the distance from the first shielding layer to the periphery of the insulating layer is greater than 0.1mm, and the coverage between the inner edge of the first shielding layer and the outer edge of the second shielding layer is greater than or equal to 2mm.

Preferably, the first shielding layer is embedded in the insulating layer in a manner that: forming the insulating layer around the first shielding layer by injection molding foaming of an insulating material; alternatively, the insulating layer is formed by bonding a plurality of insulating material layers around the first shielding layer.

Preferably, the thickness of the insulating layer ranges from 0.2mm to 5mm;

the insulating layer is made of plastic or polymer material with insulating property;

the tensile failure rate of the insulating layer is greater than 15%.

The embodiment of the specification also provides a steering wheel, which comprises a steering wheel foam, leather and a steering wheel release hand sensor;

the steering wheel release sensor is arranged on the steering wheel foam body through the leather.

Preferably, the steering wheel further comprises a heating pad, and the heating pad is arranged between the second shielding layer and the steering wheel foaming body;

the heating pad includes a heating substrate and a heating wire connected to the heating substrate;

the insulating layer is made of polyurethane plastic or polyethylene plastic;

the heating base material is made of polyurethane material.

The embodiment of the present disclosure also provides a method for arranging relevant areas of a steering wheel separation sensor, which is characterized by comprising the steps of: configuring a plurality of shielding layers by means of a conductive fabric formed of at least nickel-coated polyester fibers or polyester amine threads, the sensing layer being configured with at least one sensing area, and at least one of said sensing areas being configured to correspond to at least two of said shielding layers; the shielding layer and the sensing layer are separated by an insulating layer.

Compared with the prior art, the beneficial effects that above-mentioned at least one technical scheme that this description embodiment adopted can reach include at least:

according to the shielding layer structure, the sensing layers and the shielding layers are separated by the insulating layers, the shielding layers at a plurality of different positions can be correspondingly arranged according to the positions of the sensing regions on the steering wheel, the shielding layers are conductive fabrics formed by at least nickel-coated polyester fibers or polyester amine wires, at least one sensing region corresponds to at least two shielding layers, the probability of insufficient coverage of the shielding layers due to a complex structure of the steering wheel can be reduced, and meanwhile the probability of short circuit between the shielding layers at the edge due to pulling of leather on the sensing layers can be reduced.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic cross-sectional view of a first steering wheel release sensor arrangement highlighted in this application;

FIG. 2 is a schematic partial cross-sectional view of a second steering wheel release sensor arrangement of the present application;

FIG. 3 is a schematic top view of a second steering wheel release sensor arrangement highlighted in this application;

FIG. 4 is a schematic top view of an external connector in a second steering wheel release sensor arrangement highlighted in the present application;

FIG. 5 is a schematic illustration of the insulating layer and the first shielding layer highlighted in this application;

FIG. 6 is a schematic diagram highlighting the opposing faces between the insulating layer and the first shielding layer in the present application;

FIG. 7 is a schematic cross-sectional view of a third steering wheel release sensor arrangement highlighted in this application;

FIG. 8 is a schematic top view of a third steering wheel release sensor arrangement highlighted in this application;

FIG. 9 is a schematic top view of an external connector in a third steering wheel release sensor arrangement highlighted in the present application;

fig. 10 is a schematic diagram of a prior art protruding steering wheel away hand sensor arrangement.

Reference numerals: 1. an induction layer; 2. double faced adhesive tape; 3. an insulating layer; 4. outgoing lines of the first shielding layer; 5. a first shielding layer; 6. a second shielding layer; 7. grounding; 8. heating the substrate; 9. heating the metal wire; 10. a distance between the second shielding layer outer edge and the sensing layer outer edge; 11. leather; 12. steering wheel foam; 13. a first sensing region; 14. a second sensing region; 15. a third sensing region; 16. an amount of coverage between the first shielding layer inner edge and the second shielding layer outer edge; 17. an opposite surface between the insulating layer and the first shielding layer; 18. a connector; 19. a first tongue; 20. a second tongue; 21. a third tongue; 22. a shield layer is present.

Detailed Description

Embodiments of the present application are described in detail below with reference to the accompanying drawings.

Other advantages and effects of the present application will become apparent to those skilled in the art from the present disclosure, when the following description of the embodiments is taken in conjunction with the accompanying drawings. It will be apparent that the described embodiments are only some, but not all, of the embodiments of the present application. The present application may be embodied or carried out in other specific embodiments, and the details of the present application may be modified or changed from various points of view and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.

It is noted that various aspects of the embodiments are described below within the scope of the following claims. It should be apparent that the aspects described herein may be embodied in a wide variety of forms and that any specific structure and/or function described herein is merely illustrative. Based on the present application, one skilled in the art will appreciate that one aspect described herein may be implemented independently of any other aspect, and that two or more of these aspects may be combined in various ways. For example, apparatus may be implemented and/or methods practiced using any number and aspects set forth herein. In addition, such apparatus may be implemented and/or such methods practiced using other structure and/or functionality in addition to one or more of the aspects set forth herein.

It should also be noted that the illustrations provided in the following embodiments merely illustrate the basic concepts of the application by way of illustration, and only the components related to the application are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complicated.

In addition, in the following description, specific details are provided in order to provide a thorough understanding of the examples. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details.

In view of this, the applicant has conducted intensive studies and improved searches on the steering wheel release sensor, and the sensing layer 1 and the shielding layer of the steering wheel release sensor, and found that: as shown in fig. 10, the capacitive sensor body for detecting the vehicle steering wheel from hand comprises a sensing layer 1 (sensor layer, also called sensor layer), an existing shielding layer 22 and an insulating layer 3, wherein the insulating layer 3 is connected between the sensing layer 1 and the existing shielding layer 22 through a double faced adhesive tape 2, the sensing layer 1 and the existing shielding layer 22 are composed of conductive fabrics or metal meshes, the sensing layer 1 is the outermost conductive cloth of the capacitive sensor for detecting the vehicle steering wheel from hand, in the steering wheel coating process, in order to make the coating effect better, the steering wheel skin is pulled, the steering wheel skin and the sensing layer 1 are connected together through the double faced adhesive tape 2, and the surface of the steering wheel skin is rough, so that the adhesive force between the steering wheel skin and the sensing layer 1 is relatively large, and meanwhile, the adhesive force between the sensing layer 1 and the insulating layer 3 is relatively small, so that the sensing layer 1 can generate displacement along the pulling direction in the pulling process, and the sensing layer 1 can exceed the range of the existing shielding layer 22. The sensing layer 1 exceeds the existing pair of shielding layers 22, which causes a series of signal problems for hands-off detection, the signals can be easily disturbed, resulting in unstable performance, which is a situation that needs to be reduced or even avoided.

Based on this, the technical solutions provided by the embodiments of the present application are described below with reference to the accompanying drawings.

The embodiment of the specification provides a steering wheel release sensing sensor: as shown in fig. 1, comprises a sensing layer 1, an insulating layer 3 and a shielding layer; an insulating layer 3 separates the sensing layer 1 from a shielding layer, the sensing layer 1 comprising at least one sensing area, the shielding layer comprising a conductive fabric formed of at least nickel coated polyester fibers or polyester amine wires; the shielding layer is configured in plurality, and at least one sensing area is configured to correspond to at least two shielding layers. The sensing layer 1 may comprise one, two, three or the like sensing areas, which may be arranged according to the location of the components on the steering wheel, such as the spokes, the locations on the rim or the like. The shielding layer may be configured of two, three, four, etc. For example, when the sensing layer 1 includes a sensing area, the sensing area may correspond to an upper portion of the sensing rim, an upper portion of a spoke, a connection portion between spokes of the rim, and the like, and then the sensing area may correspond to two (shown in fig. 1), three, four, and the like shielding layers, the shielding layers may be respectively disposed at different positions of the insulating layer 3, may respectively correspond to the sensing areas at different positions of the steering wheel, the shielding layers may jointly act on all the sensing areas, a probability of insufficient coverage of the shielding layers due to a complex structure of the steering wheel may be reduced, when the sensing layer 1 is coated on the steering wheel through a coating process, the leather 11 may pull the sensing layer 1, at this time, the sensing area corresponds to the shielding layers at a plurality of positions, and the shielding layers jointly act on the shielding layers to reduce parasitic leather between the sensing area and a vehicle component, and may reduce a probability of a short circuit with the shielding layer at an edge of the sensing layer 1 due to pulling of the sensing layer 11 on the sensing layer 1, and may improve shielding stability. For example, when the sensing layer 1 includes three sensing areas, the sensing areas may correspond to different positions on the steering wheel respectively, the shielding layers may be arranged in three and located at different positions of the insulating layer 3, one of the shielding layers may be opposite to the position of the sensing layer 1, and the shielding layers are smaller than or equal to the sensing layer 1, an overlapping portion may be formed between the shielding layers, and the sensing areas of the sensing layer 1 are covered by the shielding layers together, where at least one sensing area may correspond to two or three shielding layers respectively, i.e. at least one sensing area may be covered by at least two shielding layers, so that the probability of insufficient coverage of the shielding layer caused by the complex structure of the steering wheel may be reduced, and the probability of short circuit with the shielding layer at the edge of the sensing layer 1 due to pulling of the leather 11 on the sensing layer 1 may also be reduced, thereby improving the shielding stability.

In one embodiment, as shown in fig. 2 and 3, the plurality of shielding layers includes a first shielding layer 5 and a second shielding layer 6; the first shielding layer 5 is arranged in the insulating layer 3, the second shielding layer 6 is arranged on the surface of the insulating layer 3, and the projection of the first shielding layer 5 and the second shielding layer 6 in the direction perpendicular to the insulating layer 3 completely covers the sensing area. Specifically, the sensing layer 1 may include a first sensing area 13, a second sensing area 14, and a third sensing area 15, and the first sensing area 13, the second sensing area 14, and the third sensing area 15 may respectively correspond to the first shielding layer 5 and the second shielding layer 6. The first sensing area 13 is connected with the first tongue piece 19, the second sensing area 14 is connected with the second tongue piece 20, the third sensing area 15 is connected with the third tongue piece 21, the second shielding layer 6 and the sensing layer 1 can be located at opposite positions, the second shielding layer 6 is smaller than or equal to the sensing layer 1, the first shielding layer 5 and the second shielding layer 6 have overlapping parts, and the first shielding layer 5 and the second shielding layer 6 jointly cover all sensing areas of the sensing layer 1.

In one embodiment, as shown in fig. 2 and 3, the first shielding layer 5 is annular and covers the outer edge region of the insulating layer 3, and the second shielding layer 6 is sheet-shaped and covers the central region of the insulating layer 3. I.e. the first shielding layer 5 and the second shielding layer 6 may be fully covered with the insulating layer 3, the first shielding layer 5 may cover the outer edge portion of the second shielding layer 6, and the first shielding layer 5 may cover the outer edge portion of the sensing layer 1.

In one embodiment, the first shielding layer 5 is connected to the second shielding layer 6 through a wire; alternatively, as shown in fig. 2 and 3, the first shielding layer 5 is provided by a wire ground 7. The lead wires used as the lead wires 4 of the first shielding layer 5 can be metal wires or printed connecting wires, for example, the first shielding layer 5 is connected with the second shielding layer 6 through the metal wires with insulating covers, the second shielding layer 6 and the induction layer 1 are connected through the lead wires, so that the first shielding layer 5 and the second shielding layer 6 form an equipotential body, the shielding effect on the outside is better, or the first shielding layer 5 is not connected with the second shielding layer 6, but the first shielding layer 5 is grounded through the metal wires with insulating covers 7, the first shielding layer 5 is connected with the ground, and indirect shielding is performed, so that the first shielding layer 5 forms a passive shielding effect, and also forms a shielding effect on the outside electric signals and the magnetic signals.

In one embodiment, as shown in fig. 2 and 3, the first shielding layer 5 is embedded in the edge portion of the insulating layer 3, and the distance between the first shielding layer 5 and the periphery of the insulating layer 3 is greater than 0.1mm, and the coverage between the inner edge of the first shielding layer 5 and the outer edge of the second shielding layer 6 is greater than or equal to 2mm. Specifically, for example, the first shielding layer 5 is embedded in the middle of the edge portion of the insulating layer 3, and a certain gap is formed between the first shielding layer 5 and the upper and lower positions of the periphery of the insulating layer 3, for example, greater than 0.1mm. The embedded first shielding layer 5 is to have an overlapping area with the second shielding layer 6 and to cover the sensing layer 1 completely. The first shielding layer 5 covers and overlaps the outer edge of the second shielding layer 6, and the first shielding layer 5 covers the outer edge of the induction layer 1, the covering amount 16 between the inner edge of the first shielding layer and the outer edge of the second shielding layer is more than or equal to 2mm, and the distance 10 between the outer edge of the second shielding layer and the outer edge of the induction layer is more than or equal to 3mm.

In one embodiment, the thickness of the insulating layer 3 ranges from 0.2mm to 5mm. The material of the insulating layer 3 is plastic or a polymer material having insulating properties, such as polyurethane, polyethylene, polyvinyl chloride, polystyrene, or the like. The insulating layer 3 has good stretching and ductility, and the stretching fracture rate of the insulating layer 3 is more than 15%.

In one embodiment, the sensing layer 1 and the shielding layer are conductive fabrics of polyester fiber and nickel plating, and the nickel content of the polyester fiber is 20-70% by mass.

In an embodiment, the induction layer 1 and the insulation layer 3 and the shielding layer are respectively connected by one of double faced adhesive tape 2, glue, sewing and welding. The double-sided tape 2 is here, for example, a double-sided tape, and the shielding layer comprises a first shielding layer 5 and a second shielding layer 6.

In one embodiment, as shown in fig. 2 and 4, the first shielding layer 5 circumscribes the connector 18.

In one embodiment, as shown in fig. 5 and 6, the first shielding layer 5 is embedded in the insulating layer 3 in the following manner: forming an insulating layer 3 around the first shielding layer 5 by injection molding foaming using an insulating material; alternatively, the insulating layer 3 is formed by bonding a plurality of insulating material layers around the first shielding layer 5. For example, the insulating material is a polyurethane material or a polyethylene material, the insulating material layer is a polyethylene layer, for example, and the opposite surface 17 between the insulating layer and the first shielding layer may also be bonded by means of a double sided tape 2 or the like. As shown in fig. 1 and 5, the first shielding layer 5 in the insulating layer 3 may be connected together by a wire and the second shielding layer 6 at the time of injection molding.

In an embodiment, the shielding layer may be a conductive fabric made of a conductive material such as copper wire, metal mesh, conductive paste, and the like, which plays a role in shielding. Specifically, the conductive fabric is conductive copper wires with insulating paint on the outer surface, conductive paste containing liquid of metallic copper or liquid of metallic silver.

In an embodiment, as shown in fig. 7 and 8, the difference is that a plurality of shielding layers are combined as one first shielding layer 5, the first shielding layer 5 is injection molded in the middle of the polyethylene insulation layer 3, and the first shielding layer 5 completely covers the sensing layer 1, i.e. the corresponding size of the first shielding layer 5 is larger than the corresponding size of the sensing layer 1. As shown in fig. 7 and 9, the first shielding layer 5 circumscribes the connector 18.

The embodiment of the present disclosure also provides a steering wheel, as shown in fig. 1 and 2, including a steering wheel foam 12, leather 11, and the steering wheel sensor of the above embodiment; the steering wheel release sensor is arranged on the steering wheel foam 12 by means of leather 11.

In one embodiment, as shown in fig. 1 and 2, the steering wheel further comprises a heating pad, which is disposed between the second shielding layer 6 and the steering wheel foam 12; the heating pad includes a heating substrate 8 and a heating wire 9 connected to the heating substrate 8; the material of the insulating layer 3 is polyurethane plastic or polyethylene plastic; the heating substrate 8 is a polyurethane material. The heating metal wire 9 is, for example, a copper wire with an insulating coating on the outside, and the double-sided tape 2 may be bonded between the leather 11 and the outside of the induction layer 1, between the induction layer 1 and the insulating layer 3, between the insulating layer 3 and the shielding layer, and between the second shielding layer 6 and the heating substrate 8.

The embodiment of the present disclosure further provides a method for disposing relevant areas of a steering wheel sensor, as shown in fig. 1 and fig. 2, for manufacturing the steering wheel sensor according to any one of the foregoing embodiments, including: the induction layer 1 is provided with at least one sensing area by a plurality of shielding layers formed by conductive fabrics formed by at least nickel-coated polyester fibers or polyester amine wires, and at least one sensing area is provided to correspond to at least two shielding layers; the shielding layer and the sensing layer 1 are separated by an insulating layer 3.

According to the method, the sensing layer 1 of the sensor is arranged in a distance sensing mode, and the relevant area of the shielding layer is arranged in a distance sensing mode, so that the signal stability is enhanced, the production requirement can be met, and the shielding effectiveness is better. The conductive fabric such as copper wires, metal nets, conductive paste and other conductive materials is added at the edge of the insulating layer 3, so that the insulating layer 3 plays a shielding role, and the insulating layer 3 plays an insulating effect and a shielding effect at the same time, so that the excessive sensing layer 1 can be effectively protected and external interference signals can be shielded. The problem of signal interference due to the fact that the sensing layer 1 exceeds the shielding layer as a result of the steering wheel process is avoided.

In this specification, identical and similar parts of the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, the description is relatively simple for the embodiments described later, and reference is made to the description of the foregoing embodiments for relevant points.

The foregoing is merely specific embodiments of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions easily conceivable by those skilled in the art within the technical scope of the present application should be covered in the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims (10)

1. A steering wheel release sensing sensor comprises a sensing layer (1), an insulating layer (3) and a shielding layer; -said insulating layer (3) separating said sensing layer (1) and said shielding layer, said sensing layer (1) comprising at least one sensing area, characterized in that said shielding layer comprises a conductive fabric formed of at least nickel coated polyester fibers or polyester amine wires;

the shielding layer is configured in a plurality, and at least one sensing area is configured to correspond to at least two shielding layers.

2. Steering wheel separation sensing sensor according to claim 1, characterized in that a plurality of said shielding layers comprises a first shielding layer (5) and a second shielding layer (6);

the first shielding layer (5) is arranged in the insulating layer (3), the second shielding layer (6) is arranged on the surface of the insulating layer (3), and the projection of the first shielding layer (5) and the second shielding layer (6) in the direction perpendicular to the insulating layer (3) completely covers the sensing area.

3. Steering wheel release sensor according to claim 2, characterized in that the first shielding layer (5) is ring-shaped covering the outer edge area of the insulating layer (3) and the second shielding layer (6) is sheet-shaped covering the central area of the insulating layer (3).

4. A steering wheel separation sensor according to claim 3, characterized in that the first shielding layer (5) is wired to the second shielding layer (6);

alternatively, the first shielding layer (5) is arranged through a wire ground (7).

5. A steering wheel off-hand sensor according to claim 3, characterized in that the first shielding layer (5) is embedded in an edge portion of the insulating layer (3), and the first shielding layer (5) is spaced from the periphery of the insulating layer (3) by a distance of more than 0.1mm, and the amount of coverage between the inner edge of the first shielding layer (5) and the outer edge of the second shielding layer (6) is more than or equal to 2mm.

6. Steering wheel release sensor according to claim 5, characterized in that the first shielding layer (5) is embedded in the insulating layer (3) in such a way that: -injection-foaming the insulating layer (3) around the first shielding layer (5) using an insulating material; alternatively, the insulating layer (3) is formed by bonding a plurality of insulating material layers around the first shielding layer (5).

7. Steering wheel off-hand sensor according to claim 6, characterized in that the thickness of the insulating layer (3) ranges from 0.2mm to 5mm;

the material of the insulating layer (3) is plastic or polymer material with insulating property;

the tensile fracture rate of the insulating layer (3) is more than 15%.

8. A steering wheel comprising a steering wheel foam (12), leather (11) and a steering wheel release sensor according to any one of claims 2 to 7;

the steering wheel release sensor is arranged on the steering wheel foam (12) through the leather (11).

9. Steering wheel according to claim 8, characterized in that it further comprises a heating pad arranged between the second shielding layer (6) and the steering wheel foam (12);

the heating pad comprises a heating substrate (8) and a heating wire (9) connected to the heating substrate (8);

the insulating layer (3) is made of polyurethane plastic or polyethylene plastic;

the heating base material (8) is made of polyurethane material.

10. A method for arranging relevant areas of a steering wheel sensor, characterized in that it is used for manufacturing the steering wheel sensor according to any one of claims 1 to 7, comprising: the sensing layer (1) is provided with at least one sensing area by a plurality of shielding layers formed by conductive fabrics formed by at least nickel-coated polyester fibers or polyester amine wires, and at least one sensing area is provided corresponding to at least two shielding layers; the shielding layer and the induction layer (1) are separated by an insulating layer (3).