FLEXIBLE AND STRETCHABLE HEATER BASED ON CONDUCTIVE TEXTILE OR CONDUCTIVE POLYMERIC FOAM

Abstract

An electric heating device, in particular for automotive application, includes at least one heating member and electric terminals that are provided as electric connections connectable to an electric power supply. The heating member includes at least one dielectric, planar, flexible carrier formed as a textile carrier or as a polymeric foam carrier and having an upper surface and an opposite lower surface arranged in parallel to the upper surface, wherein at least one out of the upper surface and the lower surface is equipped with an attached continuous layer of electrically conductive material, which extends over a major part of an area of the respective surface of the at least one flexible carrier. At least one electric terminal is arranged at and electrically connected to each end of the electrically conductive material layer of each heating member.

Claims

1. An electric heating device, in particular for automotive application, comprising: at least one heating member including at least one dielectric, planar, flexible carrier being formed as a textile carrier or as a polymeric foam carrier and having an upper surface and an opposite lower surface arranged in parallel to the upper surface, wherein at least one out of the upper surface and the lower surface is equipped with an attached continuous layer of electrically conductive material, which extends over a major part of an area of the respective surface of the at least one flexible carrier, and at least one electric terminal arranged at and electrically connected to each end of the electrically conductive material layer of each heating member, wherein the electric terminals are provided as electric connections that are connectable to an electric power supply.

2. The electric heating device as claimed in claim 1, wherein, in an operable state, the at least one heating member comprises a double bend in opposite directions and perpendicular to a direction of the largest extension such that in a direction perpendicular to the upper and the lower surface, at least one overlap region is formed comprising at least three regions of the continuous electrically conductive layer of the at least one heating member.

3. The electric heating device as claimed in claim 1, comprising a plurality of heating members that are arranged such that portions of their respective continuous electrically conductive layers are electrically connected in parallel.

4. The electric heating device as claimed in claim 1, wherein the continuous electrically conductive material layer comprises at least one continuous region that is split up in a plurality of strips running in parallel to the direction of the largest extension, and being electrically connected in parallel, wherein a total sum of widths of the strips is smaller than a width of the continuous electrically conductive material layer adjacent to ends of the strips.

5. The electric heating device as claimed in claim 1, wherein the at least one heating member comprises at least one region of a 180° direction change in a plane.

6. The electric heating device as claimed in claim 1, wherein the electrically conductive layer includes at least one region of a 180° direction change in a plane, which comprises a plurality of meander-shaped strips whose ends are electrically connected, and wherein a ratio of a length and a width of each of the meander-shaped strips is essentially equal.

7. The electric heating device as claimed in claim 1, wherein at least one electrically conductive layer of the at least one heating member comprises at least one material out of a group formed by copper, nickel, silver, manganese and a combination of at least two of these.

8. The electric heating device as claimed in claim 1, comprising a plurality of heating members, which are attached one on the other at the same location in a mutually insulated way, and that are electrically connectable in parallel to the electric power supply.

9. The electric heating device as claimed in claim 1, wherein the electric heating device comprises a vehicle steering wheel heater.

10. The electric heating device as claimed in claim 1, wherein the at least one heating member of the electric heating device comprises an antenna of a capacitive sensing device for automotive application.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Further details and advantages of the present invention will be apparent from the following detailed description of not limiting embodiments with reference to the attached drawing, wherein:

[0041] FIG. 1 schematically illustrates a possible embodiment of an electric heating device in accordance with the invention in a plan view,

[0042] FIG. 2 schematically illustrates a detail of an alternative embodiment of an electric heating device in accordance with the invention in a perspective view,

[0043] FIG. 3 schematically illustrates another alternative embodiment of an electric heating device in accordance with the invention in a perspective view, and

[0044] FIG. 4 schematically illustrates another alternative embodiment of an electric heating device in accordance with the invention in a plan view.

[0045] In the various figures, same parts are always provided with the same reference numerals. Thus, they are usually described only once.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0046] FIG. 1 schematically illustrates a possible embodiment of an electric heating device 10 in accordance with the invention. The electric heating device 10 is intended and configured to be used for heating a vehicle steering wheel (not shown).

[0047] The electric heating device 10 comprises one heating member 12. The heating member 12 includes a dielectric, planar, flexible carrier 14 that is formed as a textile carrier completely made from polyester. The textile carrier has a longish belt-like shape with two portions having essentially straight largest extensions and a plurality of small transverse deviations, and a low cross-section with an upper surface 16 and an opposite lower surface (not shown), which is arranged in parallel to the upper surface 16. The upper surface 16, which in FIG. 1 coincides with the drawing plane, is equipped with an attached continuous layer of electrically conductive material 18 consisting of nickel. In this specific embodiment, the nickel layer 18 has been applied to the upper surface 16 by using a physical vapor deposition (PVD) process, namely by vacuum evaporation deposition. Alternatively, it may have been attached by another PVD process or galvanically by employing an electroplating process. The nickel layer 18 extends over a major part of more than 90% of the area of the upper surface 16.

[0048] In alternative embodiments of the heating member, the textile carrier may be replaced by a polymeric foam carrier.

[0049] Further, the electric heating device 10 includes two electric terminals 20, 22. One electric terminal 20, 22 each is arranged at and electrically connected to ends of the electrically conductive material layer 18 of the heating member 12. The electric terminals 20, 22 serve as electric connections to an electric power supply that may be positioned remote from the steering wheel within the vehicle.

[0050] In a middle region of its longish extension, the heating member 10 comprises a region of a 180° direction change 24 in a plane, by which a potentially disturbing return line for an electric current flowing through the electrically conductive material layer 18 can be avoided.

[0051] The nickel layer 18 has a uniform thickness t and width w along a length of extension l. Its electric resistance R can be obtained from a sheet resistance R.sub.S and its geometric dimensions by

[00001]$\begin{array}{cc}R=R_S.Math.\frac{l}{w},R_S:=\frac{\rho }{t}& \left(1\right)\end{array}$

wherein ρ denotes the specific electric resistivity of the electrically conductive material layer 18.

[0052] For the following parameters [0053] t=5.Math.10.sup.−6 m [0054] w=10.sup.−2 m [0055] l=1 m, and [0056] ρ=7.2.Math.10.sup.−8 Ω.Math.m (for nickel)
a heating power of about 100 W can be achieved by providing a power supply voltage of 12 V. Of course, lower average heating power levels can be achieved for instance by applying a reduced operating voltage or by pulse-width modulation techniques, as is well known in the art.

[0057] The heating member 12 pursuant to FIG. 1 shows a total electric resistance of about 1.4Ω and is further intended to be used as an antenna of the capacitive sensing device for automotive sensing applications, in particular for use in a hands-on detection capacitive sensing device, as is known in the art for instance from WO 2016/096815 A1, which document shall hereby be incorporated by reference in its entirety with effect for those jurisdictions permitting incorporation by reference.

[0058] FIG. 2 schematically illustrates a heating member 32 of an alternative embodiment of an electric heating device 30 in accordance with the invention.

[0059] The heating member 32 includes a dielectric, planar, flexible carrier 34 that is formed as a textile carrier that is completely made from polyamide. The textile carrier has a longish, straight belt-like shape and a low cross-section with an upper surface 36 and an opposite lower surface 38, which is arranged in parallel to the upper surface 36. The upper surface 36 is equipped with an attached continuous layer of electrically conductive material 40 comprising a mixture of nickel and copper. The electrically conductive material layer 40 has a uniform thickness t and width w along a length of extension. The electrically conductive material layer 40 may have been applied to the upper surface 36 by using a PVD process, namely by a sputtering process, in which nickel and copper are simultaneously deposited on the flexible carrier 34. The use of another PVD process that appears suitable to those skilled in the art is also contemplated.

[0060] For illustration purposes, FIG. 2 shows the heating member 32 in a somewhat expanded view. In an operable state, the heating member 32 comprises a double bend 42 in opposite directions and perpendicular to a direction of the largest extension 44 of the flexible carrier 34. By the double bend 42, an overlap region 46 is formed in a direction perpendicular to the upper surface 36 and the lower surface 38. The overlap region 46 comprises three regions of the continuous electrically conductive layer 40 of the heating member 32. In the operable state, the three regions are in tight contact and two of them are electrically connected in parallel. The electric resistance per unit length is reduced in the overlap region 46 compared to a balance of the heating member 32, and thus, a heat flux density is also reduced when the heating member 32 is put into operation.

[0061] FIG. 3 schematically illustrates another alternative embodiment of an electric heating device 50 in accordance with the invention in a perspective view. The electric heating device 50 comprises a plurality of five heating members 52-60, a first 52 and a second 54 of which are identically designed to the heating member 12 of the electric heating device 10 pursuant to FIG. 1. In contrast to these two heating members 52, 54, a lower surface of the third 56, fourth 58 and fifth heating member 60, respectively, is equipped with an attached continuous layer of electrically conductive material, namely nickel. The third heating member 56 is arranged in a region of a 180° direction change 62. The fourth 58 and the fifth heating member 60 are arranged to cover ends of the two identical heating members 52, 54. It is noted herewith that the terms “first”, “second”, etc. are used in this application for distinction purposes only, and are not meant to indicate or anticipate a sequence or a priority in any way.

[0062] The two identical heating members 52, 54 are attached one on the other at the same location in a mutually electrical insulated way connected by adhesive bonds, and are connectable in parallel to an electric power supply by electric terminals located at their ends (not shown), similar as in the embodiment pursuant to FIG. 1. By that, a heating power level of the electric heating device 50 can be doubled compared to the embodiment pursuant to FIG. 1 when put into operation. As the third heating member 56 is equipped with the electrically conductive material layer on the lower surface, in an operational state portions of the electrically conductive material layer of the second heating member 54 and the third heating member 56, respectively, are electrically connected in parallel. Thus, the electric resistance per unit length is reduced by the third heating member 56 compared to the balance of the electric heating device 50, and thus, a heat flux density is reduced in the region of a 180° direction change 62 when the electrical heating device 50 is put into operation. By the same principle, a heat flux density is reduced in a region comprising the ends of the two identical heating members 52, 54 for avoiding an occurrence of hot spots during operation.

[0063] FIG. 4 schematically illustrates another alternative embodiment of an electric heating device 70 in accordance with the invention in a plan view. The electric heating device 70 has a heating member 72 whose outward shape resembles that of the heating member 12 of the electric heating device 10 pursuant to FIG. 1.

[0064] The heating member 72 includes a dielectric, planar, flexible carrier 74, which is formed as a textile carrier that is completely made from polyester. The textile carrier has a longish belt-like shape with two portions having an essentially straight largest extension and a plurality of small transverse deviations, and a low cross-section with an upper surface 76 and an opposite lower surface (not shown), which is arranged in parallel to the upper surface 76. The upper surface 76, which in FIG. 4 coincides with the drawing plane, is equipped with an attached continuous layer of electrically conductive material 78 consisting of nickel. The electrically conductive material layer 78 has a uniform thickness along a length of extension. The nickel layer 78 may have been applied to the upper surface 76 by using a PVD process, namely by vacuum evaporation deposition, or by any other PVD process that appears suitable to those skilled in the art. The nickel layer 78 extends over a major part of more than 95% of the area of the upper surface 76.

[0065] The electrically conductive layer 78 includes a region of a 180° direction change 80 in a plane, which comprises a plurality of three meander-shaped strips 82, 84, 86. Ends of the three meander-shaped strips 82, 84, 86 are electrically connected, so that the three strips 82, 84, 86 are electrically connected in parallel. A width of the meander-shaped strip 82 arranged at the outside of the region of the 180° direction change 80 is larger than a width of the meander-shaped strip 84 arranged at the middle part of the region of the 180° direction change 80, which in turn is larger than a width of the meander-shaped strip 86 arranged at the inside of the region of the 180° direction change 80. A length of the meander-shaped strip 82 arranged at the outside of the region of the 180° direction change 80 is larger than a length of the meander-shaped strip 84 arranged at the middle part of the region of the 180° direction change 80, which in turn is larger than a length of the meander-shaped strip 86 arranged at the inside of the region of the 180° direction change 80.

[0066] A ratio

[00002]$\frac{l}{w}$

of the respective length and the respective width of each of the meander-shaped strips 82, 84, 86 is essentially equal within the margin of ±10%. Thus, according to formula (1), an electric resistance of the meander-shaped strip 82 arranged at the outside, an electric resistance of the meander-shaped strip 84 arranged at the middle part and an electric resistance of the meander-shaped strip 86 arranged at the inside of the region of the 180° direction change 80 are equal within the given margin. As the three meander-shaped strips 82, 84, 86 are electrically connected in parallel, electric currents flowing through each of the three strips 82, 84, 86 are equal within the margin of ±10%, and a heat flux density is also equal to the same extent, avoiding an occurrence of any hot spots in this region.

[0067] Moreover, the continuous electrically conductive material layer 78 includes two continuous regions 90, 92 that are each split up in a plurality of three strips 94, 96, 98 running in parallel to a direction of the largest extension 88.

[0068] The working principle is the same for the two continuous regions 90, 92 split-up in a plurality of three strips 94, 96, 98. It will therefore be sufficient to exemplarily describe the working principle for one 90 of these continuous regions 90, 92.

[0069] The strips of the plurality of three strips 94, 96, 98 are electrically connected in parallel. A total sum of widths of the three strips 94, 96, 98 is smaller than a width of the continuous electrically conductive material layer 78 adjacent to ends of the three strips 94, 96, 98.

[0070] A ratio

[00003]$\frac{l}{w}$

of a respective length and a respective width of each of the three strips 94, 96, 98 is different. The ratio

[00004]$\frac{l}{w}$

for the strip 94 arranged at an outside of the region 90 of the heating member 72 is smaller than the ratio

[00005]$\frac{l}{w}$

for the strip 96 arranged in a middle region of the region 90 of the heating member 72, which in turn is smaller than the ratio

[00006]$\frac{l}{w}$

for the strip 98 arranged at an inside region of the region 90 of the heating member 72.

[0071] Therefore, a heat flux density per unit length for the strip 94 arranged at the outside of the heating member 72 is larger than a heat flux density per unit length for the strip 96 arranged in a middle region of the heating member 72, which in turn is larger than a heat flux density per unit length for the strip 98 arranged at an inside region of the heating member 72.

[0072] Furthermore, the continuous electrically conductive material layer includes two continuous regions 100, 102 that are split up in a plurality of ten strips running in parallel to the direction of the largest extension 88.

[0073] The working principle is the same for the two continuous regions 100, 102 split-up in a plurality of ten strips. It will therefore be sufficient to exemplarily describe the working principle for one 100 of these continuous regions 100, 102.

[0074] A total sum of widths of the ten strips is smaller than a width of the continuous electrically conductive material layer 78 adjacent to ends of the ten strips. Therefore, for a given length, a ratio

[00007]$\frac{l}{w}$

of the length and a width of the continuous electrically conductive material layer 78 adjacent to ends of the ten strips is smaller than a ratio of the length and the total sum of widths of the ten strips. As the same total electric current is flowing through the plurality of ten strips and the continuous electrically conductive material layer 78 adjacent to ends of the ten strips when the electrical heating device 70 is put into operation, a heat flux density per unit length is larger in the region 100, 102 split up in a plurality of ten strips than in the continuous electrically conductive material layer 78 adjacent to ends of the ten strips.

[0075] While embodiments of the invention have been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

[0076] Other variations to be disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality, which is meant to express a quantity of at least two. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting scope.