Patent Application
20190342949
This application claims priority to German Patent Application No. 20 2018 102 531.7, filed on May 7, 2018. The entirety of the aforementioned application is incorporated herein by reference in its entirety.
The invention relates to an electrical heating cartridge with control element.
Electrical heating cartridges with a control element that is suitable for monitoring current operating parameters, especially the temperature load of the heating cartridge, have been known for many years and widely used. They are currently used particularly in applications in the automotive industry.
One notorious problem that occurs with such electrical heating cartridges with control elements is manufacturing them with reliable and consistent processing. One major source of errors in manufacturing involves, on one hand, an exact positioning of the control element and, on the other hand, the fact that the electrical contact between the typically thin connecting wires of such control elements and thicker wires that the thin connecting wires must be connected to fails during the course of the manufacturing process. This leads to an unacceptably high scrap rate in the manufacturing of the electrical heating cartridges.
The problem of the invention therefore consists in disclosing an improved electrical heating cartridge with control element, whose structure preferably allows economical manufacturing with higher degree of reliable and consistent processing. This problem is solved by an electrical heating cartridge with the features of the preferred heating cartridge with control element. Advantageous refinements of the invention are the subject matter of the described preferred invention.
The electrical heating cartridge according to the preferred invention has an outer tubular metal casing, a control element arranged in the interior of the outer tubular metal casing, and an electrical heating element arranged in the interior of the outer tubular metal casing. Here, the electrical heating element—typically a heating wire—is shaped such that it describes a space curve that defines an interior space. This is the case, for example, for a coiled electrical heating element: here, all the coils are on a cylinder casing and thus define an interior space, namely the interior space of the cylinder bounded on the outside by this cylinder casing. Furthermore, the electrical heating element is electrically insulated from the outer tubular metal casing, preferably with a good heat-conducting material, e.g., magnesium oxide powder or granulate.
It is preferred for the invention that the control element is arranged at least in sections embedded in an electrically insulating, heat-conducting material parallel to the direction of extent of the interior space defined by the space curve described by the electrical heating element.
In a preferred way that the control element is arranged at least in sections embedded in an electrically insulating, heat-conducting material in the interior space defined by the space curve described by the electrical heating element.
Here, it is preferred if the electrical heating element is wound at least in sections on the outer surface of a coil form—for example, a molded part or pressed part made from ceramic—which is arranged in the interior of the outer tubular metal casing, if the electrical heating element is electrically insulated from the outer tubular metal casing at least in the radial direction relative to the coil axis, and if the control element is arranged embedded in an electrically insulating, heat-conducting material in the area surrounded by the outer surface of the coil form.
The whole arrangement is preferably compressed, in order to guarantee good heat transfer.
The control element could be, in particular, a control coil, i.e., a coiled wire section made from a material, whose specific resistance has such a high temperature dependency that, with the given length of the coiled wire section, temperature fluctuations can be detected with the desired accuracy by measuring the resistance of the control coil. The control element, however, could also be a PT sensor, e.g., a PT100 sensor or an NTC element.
It is preferred if the control element is arranged in the interior of a second tubular metal casing that is arranged in the space surrounded by the outer surface of the coil form. In particular, a control element constructed as a control coil can also be arranged as an assembly coiled on a second coil form in the space surrounded by the outer surface of the first coil form. In both cases, this produces a control element that is constructed as an easily manufacturable, pre-assembled, and separately testable and relatively robust assembly, in which forces introduced, for example, in the later production process can be at least partially absorbed by the second tubular metal casing or the second coil form. This is then preferred if the electrical heating element is designed for low-voltage applications, e.g., operation with 24-V operating voltage, as is often the case in the automotive industry, so that high currents occur.
Especially preferred is an improvement of the invention, in which the second tubular metal casing is arranged in a recess or hole of the coil form. In this way, the positioning accuracy, with which the control element can be placed, can be improved even more decisively, which can contribute to better control accuracy. This applies both with respect to the radial positioning accuracy, because the position is specified by the position of the recess, that is, also with respect to the axial positioning accuracy that can be specified, in particular, by the depth of the hole or recess or by a limiting of the insertion depth by a stop.
Here it is preferred if the electrical heating cartridge is closed on its connection-side end with a first closing disk that has openings for feeding through either end sections or connections of the electrical heating element and an opening for feeding through a section of the second tubular metal casing, in which the control element is arranged. Such a construction of the electrical heating cartridge simplifies the finishing, because preassembled electrical heating cartridges can be later finished to form an electrical heating cartridge with a desired type of control by inserting and fixing the control element arranged in the second tubular metal casing.
In particular, in one improvement of this embodiment of the preferred invention, the fixing is achieved in that, in the electrical heating cartridge, there is another closing disk arranged on the connection side next to the first closing disk, which has openings for feeding through either end sections or connections both of the electrical heating element and also of the control element.
The closing disks can each be made from ceramic, PTFE, Teflon, plastic, or a silicone rubber. It is preferred if the two closing disks are made from different materials.
Such a combination of materials can also be achieved by combining a closing disk and a sealing compound.
The foregoing summary, as well as the following detailed description of the preferred invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the preferred invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:
Equivalent components of equivalent embodiments are provided with identical reference symbols with prefixes “1,” “2,” “3,” and “4” to distinguish the first, second, third and fourth preferred embodiments, respectively, as long as nothing else is indicated. However, for increasing the clarity of the figures, not all reference symbols are shown in each figure.
a show a first preferred embodiment of an electrical heating cartridge 100 with outer tubular metal casing 110 with base 111, coil form 120 with opening 122, electrical heating element 130 coiled on the outer surface 121 of the coil form 120, and a control element arranged in a second tubular metal casing 141. The electrical heating element 130 is here connected by means of connecting pins 131, which are welded in this example with end sections of the electrical heating element 130. In
Variants with connections leading out from the electrical heating cartridge from both sides are also possible.
Also visible in
In the case of the first closing disk 161, there are openings 161a, 161b for feeding through end sections of the electrical heating element 130 and the opening 161c for feeding through a section of the second tubular metal casing 141 of the control element. In the case of the second closing disk 162, there are openings 162a, 162b for feeding through end sections of the electrical heating element 130 and openings 162c, 162d for feeding through connecting wires of the control element.
As can be seen particularly well in the section diagram according to
The arrows are shown with the intention of connecting the second tubular metal casing 141 in
Here, the control elements 140′, 140″, 140′″ have in common that they are each arranged in the interior of a second tubular metal casing 141 in an electrically insulating material 142, e.g., magnesium oxide, from which, their connections 143 extend on one side.
As in the case of the first embodiment, a control element that can be constructed as shown, for example, in
Also visible in
The electrical heating cartridge 400 of the fourth embodiment differs from the electrical heating cartridge 100 of the first embodiment, as shown, e.g., in
In detail, the electrical contacting of the control coil 451 can be realized in that end sections of the control coil and/or sections of the connecting wires 453 are held in holes that pass through the second coil form 452, and are contacted to each other, in particular, press-fit contacted. Of course, the contacting of the electrical heating element 430 can also be realized in an analogous way, which then leads to an electrical heating device, in which two electrical heating elements are coiled on a coil form and contacted by conductor sections inserted into holes of the coil form.
A second difference consists in that, in the electrical heating cartridge 400 shown in
It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20 2018 102 531.7 | May 2018 | DE | national |
