DE102016208267A1 - Heating module and method for producing a heating module - Google Patents

Abstract

A method for producing a heating module (2), in particular a heating module (2), which is designed for heating a reducing agent in an exhaust aftertreatment system, comprises the steps of: (A) arranging at least one heating coil (4) between a first layer (6) of a elastic heat conductive material and a second layer (8) of an elastic heat conductive material; (B) providing a compressed structure (15) by compressing the two layers (6, 8) without crosslinking the two layers (6, 8) together; (C) providing a layered structure (17) by attaching a respective metal plate (10, 12) on both sides of the compressed structure; and (D) overmolding said layered structure (17) with a heated thermoplastic material (14), said thermoplastic material (14) having a temperature sufficient to cause crosslinking of said two layers (6, 8).

Description

The invention relates to a heating module and method for producing a heating module, in particular a heating module, which is designed for heating a reducing agent in an exhaust aftertreatment system.

State of the art

To de-sting the exhaust gases of internal combustion engines, especially diesel engines, the so-called SCR technique ("selective catalytic reduction") has proven with a urea-containing reducing agent. For this purpose, systems have been developed which enable compliance with the required exhaust gas limit values with the aid of defined addition of an aqueous urea solution ("AdBlue" ^® ) into the exhaust gas system. These systems essentially comprise a tank for the urea solution, a delivery module with a filter and pump unit, a dosing unit mounted on the exhaust system and an electronic control unit.

Since the aqueous urea solution has a relatively high freezing point, which can not be arbitrarily lowered by adding anti-freeze agents without impairing the function as a reducing agent, it is necessary to heat the reducing agent supply at low outside temperatures to prevent freezing of the reducing agent.

For this purpose, usually electric heaters are used. In order to protect the actual heating element from the reducing agent, these are often coated with a plastic.

In previously known methods of manufacturing reductant heater heaters, a heating coil in contact with an aluminum body is overmolded with a reductant-resistant plastic (e.g., HDPE). For efficient heat transfer from the heating coil to the aluminum body, direct contact without air gaps is required. To ensure such good contact, a heat-conducting rubber film between the aluminum body and the heating coil is used. The rubber film is used to compensate for bumps and to avoid the occurrence of air gaps. By adding heat-conductive fillers, a good thermal conductivity of the rubber film can be ensured.

The handling of the heat-conducting rubber film is not easy and has a complex manufacturing and assembly process result.

It is therefore the objects of the invention to simplify the manufacture of a heating module which enables efficient heat transfer.

Disclosure of the invention

• (A) Anordnen wenigstens einer Heizwendel zwischen einer ersten Schicht eines elastischen wärmeleitenden Materials und einer zweiten Schicht eines elastischen wärmeleitenden Materials;
• (B) Schaffen einer verpressten Struktur durch Verpressen der beiden Schichten elastischen wärmeleitenden Materials, ohne die beiden Schichten dabei miteinander zu vernetzen;
• (C) Schaffen einer Schichtstruktur durch Anbringen von jeweils einer Metallplatte auf beiden Seiten der verpressten Struktur; und
• (D) Umspritzen der Schichtstruktur mit einem themoplastischen Material, wobei das themoplastische Material eine Temperatur hat, die ausreichend hoch ist, um eine Vernetzung der beiden Schichten des elastischen wärmeleitenden Materials zu bewirken.

A method for producing a heating module according to an embodiment of the invention, in particular a heating module, which is designed for heating a reducing agent in an exhaust gas aftertreatment system, comprises the steps:

• (A) arranging at least one heating coil between a first layer of elastic heat-conducting material and a second layer of elastic heat-conducting material;
• (B) providing a compressed structure by compressing the two layers of elastic thermally conductive material without crosslinking the two layers;
• (C) providing a layered structure by attaching a respective metal plate on both sides of the pressed structure; and
• (D) overmolding the layered structure with a thermoplastic material, wherein the thermoplastic material has a temperature sufficiently high to effect cross-linking of the two layers of the elastic thermally conductive material.

A heating module according to an embodiment of the invention, particularly adapted for heating a reducing agent in an exhaust aftertreatment system, comprises at least one heating coil disposed between a first layer of elastic heat-conducting material and a second layer of elastic heat-conducting material. The heating coil is positively connected both with the first layer and with the second layer. A heating module according to the invention has been produced in particular by a method according to the invention as described above.

A method according to the invention makes it possible, in a process which can be carried out simply and inexpensively, to produce a heating module which has the desired mechanical properties, in particular the desired stiffness, and at the same time an effective heat transfer from the heating coil to the environment, in particular liquid reducing agent Exhaust after-treatment system allows.

In one embodiment, the first layer and the second layer each contain a rubber-containing material. The mechanical and heat-conducting properties of a rubber or rubber-containing material are well suited for use in a heating module.

In particular, the first layer and the second layer may contain the same material or be made of the same material. This makes it possible to reduce the production costs of the heating module, since only a single material has to be procured and processed.

In one embodiment, the thermoplastic material in step (D) has a temperature in a range of 250 ° C to 300 ° C. Such a temperature range has proven to be well suited to crosslink the first layer and the second layer together to provide a positive-locking structure with the desired mechanical and thermal properties.

In one embodiment, steps (A) and (B) are carried out in a pressing tool, in particular a cold pressing tool. In one embodiment, step (D) is performed in an injection molding tool.

In one embodiment, the heating module additionally comprises a first metal plate and a second metal plate. The first metal plate is disposed on the side facing away from the at least one heating coil side of the first layer and the second metal plate is disposed on the side remote from the at least one heating coil side of the second layer. The metal plates impart the desired mechanical stability to the heating module and have good thermal conductivity, allowing good heat transfer from the heating coil to the surroundings of the heating module.

In one embodiment, the layer structure composed of the metal plates, the first layer, the second layer and the heating coil is surrounded by a thermoplastic material which seals the heating module in a fluid-tight manner. Such a heating module can therefore be used in fluid-containing environments, in particular a fluid tank, without an additional seal is necessary.

In one embodiment, the metal plates contain aluminum. Aluminum has mechanical and heat-conducting properties which are advantageous for use in a heating module.

Brief description of the figures

1 shows a schematic cross-sectional view of a cold press tool, as it can be used in a method for producing a heating module according to an embodiment of the invention.

2 shows a schematic cross-sectional view of a compressed structure, as prepared and used in a method for producing a heating module according to an embodiment of the invention.

3 shows a schematic cross-sectional view of an injection molding tool, with a heating module arranged therein according to an embodiment of the invention.

figure description

The 1 to 3 illustrate schematically a method of manufacturing a heating module 2 according to an embodiment of the invention.

1 shows a schematic cross-sectional view of a cold press tool 16 with one at the bottom of the 1 shown mold 16a , which has a U-shaped cross-section, and with a movable over it arranged punch 16b , The press stamp 16b especially in the direction of the mold 16a to be moved.

In the mold 16a are from bottom to top a first layer 6 an elastic heat-conducting material, at least one heating coil 4 and a second layer 8th arranged an elastic heat conductive material.

By lowering the press ram 16b in the mold 16a become the two layers 6 . 8th and the heating coil 4 pressed together. The pressing is carried out in such a way, ie in particular at a temperature and with a pressure, that the two layers 6 . 8th not crosslinked / vulcanized.

The first and the second layer 6 . 8th preferably contain a rubber-containing or rubber-containing material. The first and the second layer 6 . 8th can be made of different materials or of the same material.

The 2 shows a schematic cross-sectional view of the created in the manner described compressed structure 15 between two metal plates 10 . 12 , in particular between two aluminum plates, is arranged.

The metal plates 10 . 12 have a U-shaped cross-section, whereby between the metal plates 10 . 12 a hollow space is created. The compressed structure 15 is so arranged in the hollow space that the compressed structure 15 completely from the two metal plates 10 . 12 is enclosed. The compressed structure 15 and the two metal plates 10 . 12 together form a layer structure 17 ,

3 shows in a schematic cross-sectional view, how the layer structure 17 which the pressed structure 15 and the two metal plates 10 . 12 includes, in a schematically illustrated injection molding tool 18 is introduced. In the injection mold 18 becomes the layered structure 17 with a suitable thermoplastic material 14 molded.

The thermoplastic material 14 is heated to a temperature sufficient to cure, or vulcanize, the first layer 6 the elastic thermally conductive material and the second layer 8th to effect the elastic heat conductive material.

The thermoplastic material can be heated in particular to temperatures in the range of 250 ° C to 300 ° C.

In this way, a positive connection between the at least one heating coil 4 , the two layers 6 . 8th made of elastic, heat-conductive material and the two metal plates 10 . 12 created.

The positive-locking composite created in this way has properties, in particular high dimensional stability, which are advantageous for the use of the heating module, in particular for heating the reducing agent in an exhaust gas aftertreatment system.

The method described can be performed faster and easier than conventional methods for producing corresponding heating modules, so that production and cost advantages can be realized.

Claims (10)

Method for producing a heating module ( 2 ), in particular a heating module ( 2 ) adapted for heating a reducing agent in an exhaust aftertreatment system, the method comprising: (A) arranging at least one heating coil ( 4 ) between a first layer ( 6 ) of an elastic thermally conductive material and a second layer ( 8th ) of an elastic thermally conductive material; (B) creating a compressed structure ( 15 ) by pressing the two layers ( 6 . 8th ), without the two layers ( 6 . 8th ) to network with each other; (C) creating a layered structure ( 17 ) by attaching in each case a metal plate ( 10 . 12 ) on both sides of the compressed structure ( 15 ); (D) encapsulation of the layer structure ( 17 ) with a heat-thematic material ( 14 ), where the thermoplastic material ( 14 ) has a temperature sufficient to crosslink the two layers ( 6 . 8th ) to effect. The method of claim 1, wherein the first layer ( 6 ) and the second layer ( 6 ) each contain a rubber and / or rubber-containing material, wherein the first layer ( 6 ) and the second layer ( 6 ) contain in particular the same material. A method according to any one of the preceding claims, wherein the thermoplastic material in step (D) has a temperature between 250 ° C and 300 ° C. Method according to one of the preceding claims, wherein the steps (A) and (B) in a pressing tool ( 16 ) be performed. Method according to one of the preceding claims, wherein step (D) in an injection molding tool ( 18 ) is carried out. Method according to one of the preceding claims, wherein the metal plates ( 10 . 12 ) Aluminum. Heating module ( 2 ), in particular for heating a reducing agent in an exhaust aftertreatment system, wherein the heating module ( 2 ) at least one heating coil ( 4 ) between a first layer ( 6 ) of an elastic thermally conductive material and a second layer ( 8th ) is arranged a resilient thermally conductive material, wherein the heating coil ( 4 ) with the first layer ( 6 ) and with the second layer ( 8th ) connected is. Heating module ( 2 ) according to claim 7, additionally comprising a first metal plate ( 10 ) and a second metal plate ( 12 ), wherein the first metal plate ( 10 ) on the at least one heating coil ( 4 ) facing away from the first layer ( 6 ) and the second metal plate ( 12 ) on the at least one heating coil ( 4 ) facing away from the second layer ( 8th ) is arranged. Heating module ( 2 ) according to claim 8, wherein the metal plates ( 10 . 12 ), the first layer ( 6 ) and the second layer ( 8th ) and the heating coil ( 4 ) layer structure ( 17 ) of a thermoplastic material ( 14 ) is surrounded. Heating module ( 2 ) according to claim 9, which has been prepared by a method according to any one of claims 1 to 6.

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