WO2022042933A1

WO2022042933A1 - Method for integrally bonding heating elements to housing elements made of plastic

Info

Publication number: WO2022042933A1
Application number: PCT/EP2021/069574
Authority: WO
Inventors: Joerg Engelhardt; Guido Bernd Finnah
Original assignee: Robert Bosch Gmbh
Priority date: 2020-08-27
Filing date: 2021-07-14
Publication date: 2022-03-03
Also published as: DE102020210815A1

Abstract

The invention relates to a method for producing an integrally bonded connection (30) between a heating element (10), which contains an electrically conductive plastics material, and a housing (22) made of a plastics material (28). The following method steps are performed, where, according to a) a melt structure (20) is firstly produced on a joining side (18) of the heating element (10) during the shaping thereof, according to b) the joining side (18) is overmoulded (26) with the plastics material (28) of the housing (22), and according to c) the melt structure (20) is melted as method step b) is being performed and the integrally bonded connection (30) is formed. The invention also relates to an integrally bonded connection (30) between a heating element (10) and a housing (22) and to the use of the method to produce an integrally bonded connection (30) between a housing (22) and a planar tank heating element, filter heating element or delivery module heating element (10) of an exhaust gas aftertreatment system for internal combustion engines.

Description

Process for the material connection of heating elements

Housing elements made of plastic

technical field

The invention relates to a method for producing a material connection between a heating element, which contains an electrically conductive plastic material, and a housing made of a plastic material. Furthermore, the invention relates to a material connection between a heating element and a housing and to the use of the method for producing a material connection between a housing and a flat tank, filter or delivery module heating element of an exhaust gas aftertreatment system.

State of the art

DE 10 2012 212 798 A1 relates to a heating element and a method for its production as well as the use of the heating element. The heating element comprises at least one thermoelectric heating element, the heating element being formed at least partially with a conductive material and being supplied with electrical energy via at least two conductor tracks. According to the invention, the conductor tracks are formed using a thermal spraying process. As a result of the thermally sprayed conductor tracks, there is a good electrical connection between the conductor tracks and the conductive particles within the matrix of the conductive material of the heating element. Furthermore, there is a mechanically resilient connection of the conductor tracks to the radiator. A variety of three-dimensional shapes can be imparted to the heater, resulting in a variety of applications for the heating element. The heating element can be in the form of a tubular fluid line, so that the heating element, in addition to its actual heating function, also fulfills other structurally specified tasks. Due to the functional integration or dual functionality, this heating element results in significant design simplifications and optimization possibilities.

WO 2009/077269 A1 relates to a multi-component injection-moulded part with an integral seal. Injection molded components can have a thermoplastic insert and a thermoplastic composite element sprayed onto the insert, the at least one insert having a plurality of elevations arranged one behind the other in the melt flow direction and designed as melting tips at its interface with the composite element. The injection molded part is produced by an injection molding process in which the insert is placed in an injection mold and a composite element is injected therein. The elevations should be melted by the melt of the composite element, resulting in a material-to-material, gas-tight connection. The at least one ridge has a first slope on its melt flow upstream side, wherein the ratio of the height of a constricted cross-section to the height of the ridge is in the range between 0.6 and 0.9.

A wide variety of heating elements are used to heat bodies or media such as gases or liquids. These include ceramic PTC heating elements, metal resistance heaters or also resistance heaters based on electrically conductive plastics, as can be seen from DE 10 2012 212 798 A1. With the latter, surface heating elements can be implemented. In order to transfer the heat generated on the surface to another body that is also made of plastic material, such as a housing in which a medium to be heated or thawed is stored, the best possible connection between the two plastic materials is necessary .

In order to produce material connections, it is known that two plastic components can be connected to one another in a sealed manner by overmolding melt ribs according to WO 2009 077 269 A1 by way of multi-component injection molding.

Presentation of the invention A method is proposed for producing a material connection between a heating element, which contains an electrically conductive plastic material, and a housing made of a plastic material, in which at least the following method steps are carried out: a) Production of a melting structure on a joining side of the heating element its shaping, b) overmoulding of the joining side with the plastic material of the housing, c) melting of the melting structure when carrying out b) and formation of the bonded connection.

The method proposed according to the invention makes it possible to save on other connecting elements that would otherwise be required to form a connection between the heating element and the housing, such as snap hooks, screw connections, clip connections or the like. Furthermore, the production of a material connection proposed according to the invention results in a plane, in particular a relatively large area that promotes heat transfer, between the components heating element and housing that are materially connected to one another.

In a further development of the method proposed according to the invention, the material connection is achieved by deformation of the melt structure and embedding deformed areas in the plastic material of the components to be joined.

Following the method proposed according to the invention, the melting structure on the joining side of the heating element runs parallel to the current flow direction that occurs within the heating element, or the melting structure can alternatively run on the joining side of the heating element in the transverse direction to the current flow direction in the heating element.

In both cases, the melt structure allows, be it parallel to the direction of current flow, be it transverse to the direction of current flow in the heating element running, a very good heat transfer between the materially bonded components heating element and housing.

In particular, the material connection between the heating element and the housing can be formed by the method proposed according to the invention in such a way that the deformed areas of the melted structure are evenly spaced from one another. A uniform spacing produces a regularity in the sequence of deformed and smooth areas between the components, the heating element and the housing, which are bonded to one another.

In an alternative embodiment variant of the method proposed according to the invention, a material connection can be produced to produce a material connection between a heating element, which contains a plastic material, and a housing, which contains an electrically conductive plastic material, with the following method steps being carried out: a) Generating a melting structure on a joining side of the housing during its shaping, b) overmolding the joining side with the plastic material of the heating element and c) melting the melting structure when carrying out b) and forming the material connection.

In the alternative embodiment, the components involved are reversed and the materials interchanged, but the procedure by which the bonded connection between the heating element and the housing is made is identical.

The invention also relates to an integral connection, produced according to the above method, between a heating element containing an electrically conductive plastic material and a housing made of a plastic material, with the fusion structure on a joining side of the heating element or of the housing being raised above the joining side protrudes. the Fusing structure advantageously enables selective fusing of the fusing structure and the formation of a cohesive, sealing connection without air pockets between the parting line of the components to be cohesively connected to one another, in the present case the heating element and the housing.

In an advantageous embodiment of the materially bonded connection, the melting structure on the joining side is formed by a sequence of peaks, arches, webs, ribs, cylinders, cross webs or the like.

The materially bonded connection has a melting structure which runs as a regular pattern on the joining side parallel to a direction of current flow in the heating element or in a direction transverse to the direction of current flow within the heating element.

Finally, the invention relates to the use of the method for producing a material connection between a housing and a flat tank, filter or delivery module heating element of an exhaust gas aftertreatment system, in which a freezable reduction medium is used.

Advantages of the Invention

The solution proposed according to the invention makes it possible to save connecting elements between the components to be joined, namely the heating element and the housing. Commonly used connecting elements such as snap hooks, screws, clip connections or the like are eliminated, as are the associated assembly steps. The solution proposed according to the invention makes it possible to achieve a contact surface in the region of a joint between the heating element and housing components that are to be cohesively connected to one another, which has evenly spaced connection points. As a result, the entire surface, ie the contact surface that results between the materially bonded components heating element and housing, is available for heat transport without this being adversely affected, for example, by air pockets occurring during the joining process. The melt-on structure provided on the joining side of either the housing or the heating element, which can be designed in any geometry, can be used to create punctiform melt-on points that result in deformed areas when the melt-on structure is overmolded with a flowable plastic material, which creates a tight and strong connection when it cools down arise in the area of the joint of the material connection between the materially bonded components. Depending on the number and the regularity of the regular pattern of deformed areas in the area of the material connection, a relatively high mechanical stability of the material connection between the materially joined components, namely the heating element and the housing, can be achieved. The heat-transferring surface (interface between heating element and housing) is increased by the melt-on structure.

Brief description of the drawings

The invention is described in more detail below with reference to the drawings.

Show it:

FIG. 1 shows a representation of a heating element with a melting structure,

FIG. 2 an overmolding of the heating element according to FIG. 1 with a plastic material of a housing,

FIG. 3 shows the plan view of a heating element as shown in FIG. 1,

FIG. 4 shows a mold filling of a mold for plastic material formed on a joining side of the heating element during the overmolding of the melt structure, FIG. 5 shows an enlarged representation of a deformed area of the melted-on structure in the area of the joint between the heating element and the housing

FIG. 6 shows schematic representations of raised geometries of the melting structure on the joining side of the housing or of the heating element.

Embodiments of the invention

In the following description of the embodiments of the invention, the same or similar elements are denoted by the same reference symbols, with a repeated description of these elements being dispensed with in individual cases. The figures represent the subject matter of the invention only schematically.

FIG. 1 shows a side view of a heating element 10 which is made of a thermoplastic material, for example. 1, a first electrical contact 12 and a second electrical contact 14 run perpendicular to the plane of the drawing. The two electrical contacts 12, 14 run perpendicular to the plane of the drawing in the representation according to FIG. The representation according to FIG. 1 also shows that a melting structure 20 is formed on a joining side 18 of the heating element 10 .

Figure 2 shows an overmolding 26 of the melt structure 20 on the joining side 18 of the heating element 10.

The representation according to FIG. 2 shows that in the context of overmolding 26, the material of the melted-on structure 20 on the joining side 18 of the heating element 10 is covered by the plastic material 28, from which a housing 22 or a housing wall 24 is made. Analogously to the representation according to FIG. 1, the first electrical contact 12 and the second electrical contact 14 run parallel to one another in the direction of the plane of the drawing according to FIG Melting structure 20 when overmolding 26 the melting structure 20 with the plastic material 28 of the housing 22 or the housing wall 24, a material connection 30 results, in the present case an embedding of the geometry of the melting structure 20 in the plastic material 28 from which the housing 22 or the housing wall 24 is manufactured.

The integral connection 30 between the flat heating element 10, which is made of a thermoplastic and contains electrically conductive plastic, results in a flow of heat 32 to a medium 34, for example to a freezable reducing agent that is used in exhaust gas aftertreatment systems for exhaust gas aftertreatment of internal combustion engines.

FIG. 3 shows a top view of the flat heating element 10 from the top. As can be seen from the top view according to FIG. 3, the two electrical contacts 12, 14 run parallel to one another. According to FIG. 3, a current flow 36 occurs in the current flow direction 38 from the first electrical contact 12 to the second electrical contact 14 . The current flow direction 38 runs in the longitudinal direction 52. The melting structure 20 formed on the underside of the flat heating element 10, which is not shown in Figure 3, can either be in the form of a uniform pattern in the longitudinal direction 52 of the flat heating element 10 or perpendicular thereto, i. H. extend in the transverse direction 54 of the heating element 10 . The flow of current 36, which occurs in the direction of flow of current 38 in the flat heating element 10, results in a flow of heat 32 to a medium 34 to be heated or thawed, such as a freezable operating/auxiliary material, such as is used in the context of SCR exhaust gas aftertreatment in exhaust gas aftertreatment systems for Exhaust gases from internal combustion engines are used.

FIG. 4 schematically shows a mold filling 42 of a mold 40, into which a flowable plastic material 28 is introduced in the direction of flow 44. The housing wall 24 of the housing 22 is made from the flowable plastic material 28 as part of the overmolding 26 . The illustration according to FIG. 4 shows that the plastic material 28 creeps into the mold 40 when the mold is filled 42, heating and deforming the geometry on the joining side 18, ie the melt-on structure 20. According to the direction of flow of the plastic material 28, the mold is completely filled 42 of the mold 40 in the direction of flow 44. Once the plastic material 28 has completely filled the mold 40, the material connection 30 is created between the melted-on structure 20 on the joining side 18 of the planar heating element 10 on the one hand and the plastic material 28 from which the housing wall 24 of the housing 22 is made , on the other hand.

Figure 5 shows a schematic, enlarged representation of a deformed area 50 of the melt-on structure 20 on the joining side 18 of the planar heating element 10. The illustration according to Figure 5 shows that when the mold 40 is filled with the plastic material 28, the geometry of the melt-on structure 20 contains a deformation 46 . This means that in the area of a joint 48 between the joining side 18 of the flat heating element 10 on the one hand and the upper side of the plastic material 28 from which the housing 22, in particular the housing wall 24, is made, deformed areas 50 arise due to melting and material carryover. Within these deformed areas 50, the two components that are to be bonded to one another, heating element 10 and housing 22, claw together and form a sealing contact surface without air pockets, which enables excellent heat transfer between the two components that are bonded to one another, namely heating element 10 and housing 22 .

FIG. 6 shows, in a schematic manner, the melting structure 20 which is made on the joining side 18—in this case on the heating element 10 . The fusion structure 20 generally comprises a regular pattern of tips 56, webs 58, ribs 60, cylinders 62, cross webs 64 or arcs 68. The fusion structure 20, as shown in various geometric forms in Figure 6, can be on the joining side 18 of the heating element 10 as well as on the housing 22.

Although in the method proposed according to the invention the melt-on structure 20 is provided on the joining side 18 of the flat heating element 10 made of electrically conductive plastic material, thermoplastic, which forms an integral connection 30 with the plastic material 28 of the housing 22 or the housing wall 24, another procedure can also be used to get voted. According to this alternative procedure, the housing 22 can be produced first, on which melting points or the melting structure 20 are then formed and in a second step the plastic material 28 of the heating element 10 is cast as part of the overmolding 26 .

In both process variants, excellent heat transfer is achieved through the material connection of the two materials, i. H. a thermoplastic material 66, the heating element 10 and the housing 22 respectively; Furthermore, previously used connecting elements such as snap hooks, screws, clip connections or the like can be saved, as can the associated assembly steps.

The solution proposed according to the invention creates a flat contact surface in the area of the joint 48 between the components to be joined, i. H. the flat heating element 10 on the one hand and the housing wall 24 or the housing 22 on the other hand. A large number of deformed regions 50, which are spaced apart at regular intervals and are formed by the melted-on structure 20, can be formed so that as far as possible the entire surface between the components, heating element 10 and housing 22, which are materially bonded to one another, is available for heat transfer. As a result, hot spots that may occur with temperatures that are too high and failures can be largely avoided. As already mentioned, the individual geometries of the melting structure 20, which are formed on the joining side 18 of either the heating element 10 or the housing 22 or the housing wall 24, can be designed both in the longitudinal direction 52 and in the transverse direction 54 to the current flow direction 38. Electrical isolation from the outside is also possible. This can be realized, for example, by a cover or encapsulation.

The invention is not limited to the exemplary embodiments described here and the aspects highlighted therein. Rather, within the range specified by the claims, a large number of modifications are possible, which are within the scope of expert action.

Claims

Expectations

1. A method for producing a material connection (30) between a heating element (10), which contains an electrically conductive plastic material, and a housing (22) made of a plastic material (28) with the following method steps: a) producing a melt-on structure (20). a joining side (18) of the heating element (10) during its shaping, b) overmoulding (26) of the joining side (18) with the plastic material (28) of the housing (22), c) melting of the melting structure (20) when carrying out b) and formation of the material connection (30).

2. The method according to claim 1, characterized in that the material connection (30) is produced by deformation (46) of the melted-on structure (20) and embedding deformed areas (50) in the plastic material (28).

3. The method according to claims 1 and 2, characterized in that the melting structure (20) on the joining side (18) of the heating element (10) runs parallel to the current flow direction (38) in the heating element (10).

4. The method according to claims 1 and 2, characterized in that the melting structure (20) on the joining side (18) of the heating element (10) in the transverse direction (54) to the current flow direction (38) in the heating element (10).

5. The method according to claims 1 to 4, characterized in that the material connection (30) is formed in such a way that the deformed areas (50) of the melt-on structure (20) are regularly spaced from one another. Method for producing an integral connection (30) between a heating element (10), which contains a plastic material (28), and a housing (22), which contains an electrically conductive plastic material, with the following method steps: a) producing a melt-on structure (20) on a joining side (18) of the housing (22) during its shaping, b) overmolding (26) the joining side (18) with the plastic material (28) of the heating element (10) and c) fusing the fusing structure (20) when carrying out b ) and formation of the material connection (30). Method according to Claims 1 to 6, characterized in that the material connection (30) is formed along a joint (48) between the heating element (10) and a housing wall (24) of the housing (22). Cohesive connection (30), produced according to the method according to any one of claims 1 to 7 between a heating element (10) containing an electrically conductive plastic material, and a housing (22) made of a plastic material (28), characterized in that a Melting structure (20) on a joining side (18) of the heating element (10) or the housing (22) raised above the joining side (18) protrudes. Cohesive connection (30) according to claim 8, characterized in that the fusion structure (20) on the joining side (18) has tips (56), arches (68), webs (58), ribs (60), cylinders (62) or cross webs (64) includes. Cohesive connection (30) according to claims 8 to 9, characterized in that the melting structure (20) as a regular pattern on the joining side (18) parallel to a current flow direction (38) in the heating element (10) or in the transverse direction (54) to the current flow direction (38) runs in the heating element (10). Use of the method according to one of Claims 1 to 7 for producing a material connection (30) between a housing (22) and a flat tank, filter or delivery module heating element (10) of an exhaust gas aftertreatment system with a freezable reduction medium.