Patent Application
20220402335
This application claims priority to DE 10 2021 115 747.1, filed Jun. 17, 2021, the entire disclosure of which is hereby incorporated herein by reference.
This disclosure relates to a heating device for heating an air flow in a motor vehicle. A heating device generally of this type is known, for example, from DE 10 2018 116 747 B4.
Heating devices for heating an air flow are used in motor vehicles to heat the passenger compartment. Such heating devices usually have a plurality of heating rods, which contain PTC resistors and connection plates. Usually, as in the case of the heating device disclosed in DE 103 33 451 B4, these connection plates are designed as contact tongues, which by means of a plug-in connector are electrically connected to the control circuit. In high-voltage applications, an electrically insulated earth connection is required for each heating rod, so that each heating rod has two connection plates. A corresponding number of female plug-in connectors to accommodate the contact tongues is expensive, and requires a relatively large amount of space on the circuit board.
In order to avoid the expense associated with plug-in connectors, and to save space on the circuit board, in the heating device disclosed in DE 2018 116 747 B4 the heating rods are connected to a welding contact by way of a series of sheet metal strips and contact pieces, by means of welded connections. The welding contact is brazed onto the circuit board.
This disclosure provides a way in which heating rods of a heating device for heating an air flow in a motor vehicle can be connected to a control circuit with less expense and space requirement.
In a heating device in accordance with this disclosure, the heating rods are connected by way of busbars to a circuit board, which carries a control circuit. By connecting a plurality of heating rods to the circuit board by way of a busbar, the number of connections on the circuit board can advantageously be reduced. The connection between busbars and circuit board can also be simplified. The busbars have a body made of aluminium, or an aluminium-based alloy, which establishes contact with the heating rods by means of a welded connection, and an end piece made of copper, or a copper-based alloy, which establishes contact with the circuit board by means of a plug-in connector. In this way, a cost-effective and efficient mode of production can be implemented, which enables a form of contact with the heating rods that is suitable for high voltages and high currents.
Busbars with a body made of aluminium, or an aluminium-based alloy, can be manufactured inexpensively and welded to the connection plates of the heating rods without any problems, since the connection plates are also made of aluminium, or an aluminium-based alloy. However, aluminium and aluminium-based alloys are less suitable for a plug-in connector with a low contact resistance. The busbars of a heating device in accordance with this disclosure are therefore provided with an end piece made of copper, or a copper-based alloy, which forms the male part of a plug-in connector, by way of which an electrical contact with the circuit board is established. The end piece is preferably coated, for example with tin, a tin-based alloy, a precious metal, or a precious metal-based alloy.
The body of the busbars and their end piece can be positively connected in a form fit to each other, in particular by a shaping joining process. Particularly suitable are press joining processes, for example blind riveting, self-piercing riveting, toxing, or clinching.
In toxing, a flat, round mandrel presses plates lying on top of each other into a die with a recess. Thereby the plates are shaped and interlock with each other. There are also variants of toxing in which the opposite side remains flat, or in which a rivet is inserted, so that both sides are flat. Clinching works in principle in the same way, except that the die expands during the shaping process, wherein a high-strength and compact joint between different materials is likewise created. In this way, a gas-tight connection can be created between the materials involved, and any oxide layers that may be present can be broken up when joining the materials involved, so that a good electrical connection with a low electrical resistance can be created.
The end piece of the busbars can form a contact tongue, which interacts with a mating part mounted on the circuit board, and forms a plug-in connector. It is also possible for the end piece of the busbars to be designed as a press-in contact, which is pressed into a corresponding opening in the circuit board. The contact pin can have a bulging center section that presses against the metalized inner surfaces of an opening in the circuit board. This contact pin can be of solid design, or can have an opening, such that the bulging center section of the contact pin is formed by two sprung webs, which enclose the opening between them. By providing the center section of the contact pin with such an opening, the force required for pressing in the pin can advantageously be reduced.
Regardless of the specific design of the end piece, the latter can advantageously be inserted into an opening of the circuit board. The contact with the circuit board can be established either by way of a mating part of a plug-in connector, which part is mounted on the side of the circuit board facing away from the busbar, or by way of metalized walls of the opening in the circuit board.
Copper-based alloys are alloys that consist of more than 50% by weight of copper. Aluminium-based alloys are alloys that consist of more than 50% by weight of aluminium. Suitable copper-based alloys for the end piece of the busbar are, for example, CuSn6, CuNiSi and CuZn37. Suitable aluminium-based alloys for the body of the busbar are, for example, Al5754 H22, AlMg3, Al 6082 T6 and AlSi1MgMn.
A further advantageous refinement of this disclosure provides for the end piece of the busbar to be provided with a metallic coating. In this way, the contact resistance of the plug-in connector can be reduced even further, which is a significant advantage, in particular for high-voltage applications. The metallic coating can, for example, consist of tin, or a tin-based alloy.
The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:
The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.
The heating device shown in
The heating rods 1 project with their connection-side ends into a housing 3, in which they are connected to a control circuit for purposes of controlling the heating function.
The heating rod 1 has heating resistors (not shown) made of a PTC ceramic, with which contact plates 5 establish electrical contact. Only one of these contact plates 5 is illustrated in
The body 6a and the end piece 6b of the busbar are positively connected in a form fit to each other at the point 8, for example by toxing, clinching or another shaping joining process.
In the example shown, the end piece 6b of the busbar protrudes through the circuit board 4, and is inserted into a female plug-in connector 9. The end piece 6b thus forms a contact pin, which in this example is designed as a contact tongue.
The end piece 6b is provided with a metallic coating, for example, it is tin-plated. In this way, corrosion of the end piece can be prevented, and an advantageously low contact resistance onto the circuit board 4 can be permanently achieved.
In the example of embodiment in
The end piece 6b is also positively connected in a form fit to the body 6a of the busbar 6 in the example of embodiment of
While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 115 747.1 | Jun 2021 | DE | national |
