HEATING DEVICE FOR A MOTOR VEHICLE OPERATING FLUID TANK WITH A PTC PLASTIC ELEMENT

Abstract

A heating device (10) for a motor vehicle operating fluid tank, in particular for storing aqueous urea solution, wherein the heating device (10) has two electrical conductors (12, 14), an element (16) made from PTC plastic, which is electrically arranged between the two electrical conductors (12, 14) and is in electrical contact with the two electrical conductors (12, 14), and a shell (18, 20), which protects the electrical conductors and the PTC plastic element (16) from the outside environment (22) at least in some sections, which is characterized in that at least one electrical conductor (12, 14) is made at least in some sections from a metal foil (12, 14), in particular aluminum foil, and that the shell (18, 20) is an insulating surface, in particular a plastic film (18, 20) that is preferably bonded to the metal foil.

Claims

1. A heating device for a motor vehicle operating fluid tank comprising: at least two electrical conductors; an element made from PTC plastic arranged between two of said at least two electrical conductors and in electrical contact with said two of said at least two electrical conductors; and a shell that protects at least sections of the electrical conductors and the PTC plastic element from the outside environment; wherein at least one of the two of said at least two electrical conductors is formed at least in part from a metal foil, and that the shell is an insulating surface.

2. The heating device according to claim 1, wherein the section of the electrical conductor formed from the metal foil is a meandering conductor path.

3. The heating device according to claim 1, wherein the PTC plastic element is made by extrusion or/and injection molding or/and thermoforming from a semi-finished product.

4. The heating device according to claim 1, wherein the section of the electrical conductor formed from the metal foil is bonded to the insulating surface, by means of an adhesive or/and by means of a vacuum.

5. The heating device according to claim 1, wherein that the PTC plastic element is formed with one or two metal foils and is bonded to the metal foils by co-extrusion.

6. The heating device according to claim 1, wherein an electrically conducting material that is different from the PTC plastic is applied on at least one side of the PTC plastic that faces toward an electrical conductor.

7. The heating device according to claim 6, wherein the electrically conducting material is applied by means of a precipitation process, or by applying a liquid or paste-like electrically conductive substance.

8. The heating device according to claim 1, wherein both electrical conductors are formed at least in sections.

9. The heating device according to the preamble of claim 1, wherein the two electrical conductors are molded over or around with PTC plastic in the injection molding process.

10. The heating device according to claim 1, wherein the two electrical conductors are applied on a hard shell substrate made from PTC plastic.

11. The heating device according to claim 10, wherein the two electrical conductors are accommodated between two hard shell substrates made from PTC plastic.

12. The heating device according to claim 9, wherein an assembly comprising the electrical conductors and the PTC plastic which encases them is encased at least in sections by a plastic film.

13. The heating device according to claim 1, wherein the two electrical conductors are coaxially arranged, wherein the two PTC plastic elements are radially arranged between the two electrical conductors, and an insulating shell, is provided, which fully encases the two conductors and the PTC plastic element and extends axially jointly with them radially outside of the radial outer electrical conductor.

14. A motor vehicle operating fluid tank comprising: a filling opening; an extraction opening that is different from the filling opening; and a heating device having at least two electrical conductors, an element made from PTC plastic arranged between two of said at least two electrical conductors and in electrical contact with said two of said at least two electrical conductors, and a shell that protects at least sections of the electrical conductors and the PTC plastic element from the outside environment, wherein at least one of the two of said at least two electrical conductors is formed at least in part from a metal foil, and that the shell is an insulating surface.

15. The heating device according to claim 1, wherein at least one of the two of said at least two electrical conductors is formed at least in part from aluminum foil.

16. The heating device according to claim 1, wherein the shell comprises an a plastic film bonded to the metal foil.

17. The heating device according to claim 1, wherein the PTC plastic element is made by extrusion or/and injection molding or/and thermoforming from a plate-like semi-finished product.

18. The heating device according to claim 1, wherein the section of the electrical conductor formed from the metal foil is bonded to the insulating surface configured as a plastic film by means of an adhesive or/and by means of a vacuum.

19. The heating device according to claim 1, wherein the section of the electrical conductor formed from the metal foil is bonded to the insulating surface configured as a plastic film by means of an electrically conducting adhesive or/and by means of a vacuum.

20. The heating device according to claim 6, wherein the electrically conducting material is applied by means of chemical or galvanic precipitation or chemical or physical gas phase precipitation, or by applying a liquid or paste-like electrically conductive substance.

21. The heating device according to claim 1, wherein both electrical conductors are formed completely from a metal foil.

22. The heating device according to claim 9, wherein an assembly comprising the electrical conductors and the PTC plastic which encases them is encased completely by a plastic film.

23. The heating device according to claim 13 wherein the insulating shell is a plastic shell.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0034] The present invention will be described in the following with the aid of the enclosed drawings, wherein:

[0035] FIG. 1 shows a cross section through a first embodiment of a heating device according to the invention

[0036] FIG. 2 shows a cross section through a second embodiment of a heating device according to the invention,

[0037] FIG. 3 shows a plan view of a hard shell substrate with electrical conductors provided thereon of a third embodiment of the heating device according to the invention,

[0038] FIG. 4 shows a fourth embodiment of the heating device according to the invention, and

[0039] FIG. 5 shows a fifth embodiment of a heating device according to the invention, wherein FIG. 5a shows a cross section and FIG. 5b shows a partial longitudinal section through the heating device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] FIG. 1 shows a first embodiment of a heating device according to the invention identified overall with reference numeral 10. The heating device comprises a first metal foil 12 and a second metal foil 14 as electrical conductors and a plastic element 16 made of PTC plastic arranged between the two metal foils 12 and 14. The arrangement of the metal foils 12 and 14 as well as the PTC plastic element 16 is located between the two plastic films 18 and 20, which hermetically shield the electrically conducting components 12, 14, and 16 from the outside environment, so that neither the metal foils 12 and 14 nor the PTC plastic element 16 can be touched or wetted by a medium in the outer environment 22. This is advantageous in particular if the heating device 10 is provided for emitting heat to a substance that is chemically aggressive toward at least one of the materials of the heating device, as is the case, for example, with aqueous urea solution.

[0041] The metal foils 12 and 14 are preferably aluminum foils with a thickness of, for example, 20 to 40 μm.

[0042] The PTC plastic element 16 preferably has a thickness of approximately 500 μm and is formed from a thermoplastic plastic filled with PTC particles.

[0043] The foils 18 and 20 are preferably made from polypropylene. The two metal foils 12 and 14 are each bonded to a different pole of an electric energy source, wherein the supply lines run through the plastic films 18 and 20. The supply lines are not shown in FIG. 1.

[0044] The plastic films in the shown example have a thickness of 250 μm, so that the entire heating device 10 has a thickness of a little less than 1.1 mm. They can thus be arranged in the interior space of the tank without the heating device 10 taking up an excessive amount of tank volume, which would then be lacking for storage of the medium for which the tank is intended.

[0045] The outer environment 22 is therefore preferably the interior space of a tank.

[0046] To facilitate their processability, the metal foils 12 and 14 are bonded to the respective foils 18 and 20, which are in contact with them, that is, even before they are applied on the PTC plastic element 16. The metal foils 12 and 14 can be glued to their allocated plastic film 18 or 20, respectively, with an adhesion agent arranged between them, or can be bonded to the foils by means of a vacuum. The foils 18 and 20 can likewise be glued or laminated to the PTC plastic element 16 at the points where they come into direct contact therewith.

[0047] Since the two foils 18 and 20 are preferably made from the same plastic, the foils 18 and 20 can be welded to each other where they come into direct contact.

[0048] FIG. 2 shows a second embodiment of a heating device according to the invention in the same perspective as in FIG. 1.

[0049] Components and component sections that are identical and functionally equivalent to those in the first embodiment are provided with the same reference numeral, but increased by the number 100, in the second embodiment. The second embodiment of FIG. 2 will be described below only to the extent that it differs from the first embodiment in FIG. 1, to whose description reference is expressly made to describe the second embodiment.

[0050] The second embodiment differs from the first only in that a metal layer is applied on the surfaces 116a and 116b that face the metal foils 112 and 114, for example, by precipitation from the gas phase, as is possible by means of sputtering, in order to improve the electrical contact between the metal foils 112 and 114, on the one hand, and the PTC plastic element 116, on the other hand. The metal layers 124 and 126 are only a few nanometers thick, as is usual for a metal layer precipitated from a gas phase, but considerably improve the contact between the PTC plastic element 116 and the metal foils 112 and 114, and thus reduce the contact resistance between the indicated components.

[0051] FIG. 3 shows a part of a third embodiment 210 in a plan view.

[0052] Components and component section that are identical and functionally equivalent to those in the first or second embodiment are provided with the same reference numbers, but increased by the number 200 or 100, in the third embodiment. The third embodiment of FIG. 3 will be described below only to the extent that it differs from the first embodiment in FIG. 1 or the second embodiment in FIG. 2, to whose description reference is expressly made to describe the third embodiment.

[0053] The two electrical conductors 212 and 214 are shown shaded only to better distinguish them from the substrate 216′ which supports them. It is not a sectional representation.

[0054] The substrate 216′ can be made from PTC plastic as a 3-dimensional shell component with multiple curves or angles, for example, by means of an injection molding process or as a thermoformed shell component. The electrical conductors 212 and 214 can be applied, preferably again as metal foils, on the surface facing the observer of FIG. 3. The side of the substrate 216′ facing the observer of FIG. 3 can be either molded over with a PTC plastic or can be covered with a second PTC plastic hard shell, whose side facing the substrate 216 is complementary to the surface of the substrate 216′ facing the observer of FIG. 3, so as to completely embed the electrical conductor 212 and 214, in order to bond the two hard shells in a manner that is as gap-free as possible.

[0055] FIG. 3 can also show an altered version of an extremely advantageous heating device with the same depiction. The reference 216′ can represent, for example, a cutout of the tank wall of a motor vehicle operating fluid tank, wherein the observer in FIG. 3 faces the side facing toward the tank interior.

[0056] The conductor paths 212 and 214 can then be understood as PTC conductor paths of PTC plastic applied on the tank wall 216′. A plastic film, which is not shown in FIG. 3, made again, for example, of polyolefin, in particular polypropylene, can be applied above these, for example, by gluing or lamination on the tank wall 216′, in order to protect the conductor paths 212 and 214 against wetting by the medium to be heated by the heating device 210.

[0057] FIG. 4 shows a fourth embodiment of a heating device 410 according to the invention.

[0058] Components and component sections that are identical and functionally equivalent to those in the first, second, or third embodiment are provided with the same reference numerals increased by the numbers 300, 200, or 100 in the fourth embodiment. The fourth embodiment of FIG. 4 will be described only to the extent that it differs from the first embodiment in FIG. 1 or the second embodiment in FIG. 2 or the third embodiment in FIG. 3, to whose description reference is expressly made to describe the fourth embodiment.

[0059] The heating device 310 of the fourth embodiment shows two electrical conductors 312 and 314, preferably again made from metal foil, which are locally bridged at various points by PTC plastic elements 316′, 316″ . . . 316.sup.IX. The PTC plastic elements are here either molded around the electrical conductors 312 and 314 or formed from two half-shells, which locally accommodate sections of the electrical conductors 312 and 314 between them, or encase a hard shell of PTC plastic that supports the electrical conductors 312 and 314 on one side, wherein said hard shell is molded over with PTC plastic for a complete embedding of the conductor sections supported on the hard shell.

[0060] The conductor arrangement 312, 314 with the PTC elements 316 locally bridging them can again be covered by a plastic film or can be accommodated between two plastic films. The above-said applies to the plastic films.

[0061] FIG. 5 shows a fifth embodiment 410 of a heating device according to the invention.

[0062] Components or component sections that are identical and functionally equivalent to those in the first to fourth embodiments are provided with the same reference numerals, but increased by 400, 300, 200, or 100, in the fifth embodiment. The fifth embodiment of FIG. 5 will be described below only to the extent that it differs from the embodiments in the FIGS. 1 to 4, to whose description reference is expressly made otherwise to describe the fifth embodiment.

[0063] FIG. 5a shows here a cross sectional view of the fifth embodiment and FIG. 5b shows a partial longitudinal section view thereof.

[0064] Differently from the previous embodiments, the electrical conductors 412 and 414 are arranged here coaxially with respect to each other, while the radial space between the first electrical conductor 412 and the second electrical conductor 414, which encompasses the same on the outside, is entirely filled by a PTC plastic element 416. The coaxial assembly consisting of the first and second electrical conductors 412 and 414 and the PTC plastic element 416 arranged between them are protected radially on the outside by a plastic shell 418 that is resistant to aqueous urea solution and made, for example, from polypropylene.

[0065] The coaxial cable-type heating device 410 of the fifth embodiment is preferably flexible so that it can be arranged within the limits of its deformability in a motor vehicle operating fluid tank. Fastening devices can be locally provided for this purpose on the inside of the tank with a separation from one another for local fastening of the coaxial cable-like heating device, for example, in the form of locking clips into which the coaxial cable-like heating device 410 can be pressed. In this way, the heating device 410 having a large heat-emitting surface can be arranged in the motor vehicle operating fluid tank while avoiding all potential mounting obstacles, for example, possibly a fill level sensor or other sensors, such as temperature sensors or quality sensors for an operating fluid pump and the like.

[0066] The above presented heating devices are suited especially preferably for heating aqueous urea solution as is used in motor vehicles to reduce nitrogen oxides in the exhaust of an internal combustion engine.