This application claims the benefit of priority under 35 U.S.C. § 119 of German Application 10 2020 120 472.8, filed Aug. 4, 2020, the entire contents of which are incorporated herein by reference.
The present invention pertains to a process for manufacturing a Positive Temperature Coefficient (PTC) heating element as well as to a PTC heating element manufactured, for example, with such a process.
PTC heating elements are used in vehicle construction for heating gaseous or liquid media, for example, in order to transfer heat to the air to be introduced into the interior of a vehicle. The use of PTC heating elements is considered, above all, in purely electric motor-operated vehicles, in which other heat sources, for example, an internal combustion engine or a fuel-operated heater, are not available. Such PTC heating elements are also used in other areas, for example, for heating trains or for heating fuel cells.
An object of the present invention is to provide a process for manufacturing a PTC heating element as well as a PTC heating element, with which process and PTC heating element an efficient heating operation of a PTC heating element is achieved along with the possibility of being able to carry out the manufacturing process in a simple and cost-effective manner.
This object is accomplished by a process for manufacturing a PTC heating element, wherein the PTC heating element comprises at least one PTC component and, on at least one side of the at least one PTC component, a carrier permanently connected to the at least one PTC component, the process comprising:
a) the application of electrically conductive sinter material (material that is sinterable) to a side of at least one PTC component, which side is to be permanently connected to a carrier, or/and to at least one carrier to be connected to the at least one PTC component,
b) after carrying out step a), establishing of a contact of the at least one PTC component with at least one carrier such that sinter material, applied in step a) and intended for establishing a connection between the at least one PTC component and the at least one carrier, is positioned between the at least one PTC component and the at least one carrier, and
c) sintering of the sinter material, positioned in step b) between the at least one PTC component and the at least one carrier, to provide sintered material (material that has been sintered) by heating or/and by applying pressure.
The procedure according to the present invention for manufacturing a PTC heating element combines different aspects which are especially advantageous for the manufacturing process, on the one hand, and for the operation of a PTC heating element thus manufactured, on the other hand. The use of an electrically conductive sinter material for establishing a permanent connection between one or more PTC components and at least one carrier for such PTC components creates the possibility of providing both the mechanical connection, i.e., also the electrically conductive connection by one and the same layer of material, namely, the sinter material, which is arranged between a respective PTC component and a carrier, and which is sintered at that location to harden upon sintering. Additional material layers, which could impair, above all, the heat dissipation and hence the heating efficiency, are not necessary. Further, the process according to the present invention utilizes the essential advantage that such electrically conductive sintered materials are, in general, very good heat conductors, so that it is possible not only to produce a permanent connection with a very small number of material layers positioned between a PTC component and a carrier, but, moreover, also to use for this a material that causes only a slight impairment in the heat transmission between a PTC component and a carrier, which material has, moreover, a high heat resistance. Another advantage is that no joining working steps to be carried out in a complicated manner are necessary for establishing the permanent connection between a PTC component and a carrier.
In order to obtain, on the one hand, the thinnest possible overall construction impairing the heat conduction out of the PTC heating element as little as possible and, on the other hand, in order to make it possible to guarantee a sufficient mechanical stability, it is proposed that the sinter material, which was applied in step a) to at least one side of the at least one PTC component or/and to at least one carrier and which is provided for establishing a connection between the at least one PTC component and the at least one carrier, be applied with a layer thickness of 5 μm to 20 μm and preferably about 10 μm. This means that when sinter material intended for establishing a connection between a side of a PTC component and the carrier to be connected to the PTC component on that side is applied both to one side of a PTC component and the carrier to be connected on that side to the PTC component, the thickness of the sinter material positioned between the PTC component and the carrier corresponds to twice the layer thickness, i.e., it is, for example, in the range of 10 μm to 40 μm and it preferably equals about 20 μm.
To provide a PTC component arranged in a sandwich-like manner (sandwiched) between two carriers and connected permanently to these, it is further proposed that sinter material provided for establishing a connection between the at least one PTC component and the at least one carrier be applied in step a) to two sides of the at least one PTC component, which said sides are oriented such that these sides face away from one another, or/and that sinter material intended for establishing a connection between the at least one PTC component and the at least one carrier be applied in step a) to two carriers to be connected to the at least one PTC component on two sides of the at least one PTC component, which said sides are oriented such that they face away from one another.
In order to make it possible to induce a PTC heating element to release heat during the heating operation, it is necessary to contact it electrically. Provisions may be made for this purpose for applying in step a) a sinter material intended for establishing a connection between the at least one PTC component and the at least one carrier to at least one carrier and preferably to two carriers on a side to be positioned such that it faces the at least one PTC component and for applying sinter material intended for providing at least one contact field on a side of said at least one carrier or of both carriers, which said side is to be positioned such that it faces away from the at least one PTC component, wherein at least one sintered material connection area is formed between the sintered material intended for establishing a connection between the at least one PTC component and this at least one carrier and the sinter material intended for providing at least one contact field, and for sintering in step c) the sinter material intended for providing at least one contact field and the at least one sintered material connection area by heating or/and by applying pressure.
Very efficient utilization of the heat released by a PTC component during electrical excitation can be achieved by this at least one carrier having a PTC component connection surface area on a carrier side to be positioned such that it faces the at least one PTC component, wherein this at least one carrier is to be connected in the PTC component connection surface area to the at least one PTC component by the sinter material, which was applied in step a) and which is intended for establishing a connection between the at least one PTC component and this at least one carrier, by this at least one carrier having at least one contact field surface area on a carrier side to be positioned such that it faces away from the at least one PTC component, wherein at least one contact field is to be formed in the at least one contact field surface area by the sinter material applied in step a) for providing at least one contact field, and by the at least one contact field surface area and the PTC component connection surface area not overlapping in at least some areas and preferably not overlapping completely. Thus, the at least one contact field surface area intended for the electrical contacting does not overlap or cover the area of the PTC component in which this is connected by sintered material to one or more carriers, and thus it does not impair the release of heat from the PTC component to a medium to be heated.
In order to make it possible to guarantee a uniform and full-surface coating of a PTC component or of a carrier and hence a correspondingly uniform and full-surface connection between these, it is proposed that the sinter material be applied in step a) by screen printing. It should be noted that screen printing is advantageous as an especially simple procedure, which is also carried out precisely, for applying free-flowing, for example, pasty material. Other procedures for applying such free-flowing, for example, pasty material, for example, the application of this material to a surface to be coated and the distribution of the free-flowing material on said surface by means of a doctor blade or of such a tool, may be employed as well.
High mechanical stability along with good electrical and thermal conductivity can be guaranteed, for example, by the sinter material applied in step a) containing metallic material. The use of metallic material containing silver or/and platinum has proved to be especially advantageous.
The sinter material can be brought to a temperature in the range of 200° C. to 300° C. and preferably about 250° C. especially if the sinter material comprises metallic material containing silver and/or platinum. Carrying out the sintering process at such a comparatively low temperature ensures that a structural change brought about by an excessive heating in the material forming a PTC component, which change could impair the ability of this material to function, is avoided.
For a flat contact between one or more PTC components, the at least one carrier may have a plate-like (plate shape) configuration. In order to make it possible to provide such a carrier itself as an electrical insulator, but also as a good heat conductor, it is further proposed that the at least one carrier be made of a ceramic material. For example, such a carrier may be made of aluminum oxide (Al2O3).
In order to make it possible to achieve an essentially complete encapsulation of the at least one PTC component, it is further proposed that the at least one PTC component be arranged in step b) between two carriers to be connected to said PTC component with sinter material, which is positioned between them and is intended for establishing a connection between the at least one PTC component and a respective carrier of the two carriers, such that the at least one PTC component is enclosed at least partially by a frame arranged between the two carriers, wherein the material thickness of the frame is not greater and preferably smaller than a thickness of the at least one PTC component. Since the material thickness of the frame, measured in a direction between the carriers accommodating the frame between them, is at least not greater than the thickness of a PTC component, which thickness is measured between the two carriers, it is achieved that the positioning of the two carriers, which positioning accommodates such a PTC component between the carriers, and hence also the strength of the connection to the PTC component, are not compromised by the frame arranged between the carriers.
For a manufacturing process that can be carried out in a simple manner, the frame may be connected to one of the two carriers to be connected to the at least one PTC component before the PTC component is arranged between the two carriers.
The object mentioned in the introduction is accomplished, further, by a PTC heating element, comprising at least one PTC component and a carrier connected to same permanently by electrically conductive sintered material on at least one side, preferably on two sides of the at least one PTC component, which said sides are oriented such that they face away from one another.
The present invention will be described in detail below with reference to the attached figures. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.
In the drawings:
Referring to the drawings,
To establish a permanent connection between the PTC component 20 and the two carriers 14, 16, which connection also allows an electrical contacting, metal-containing sinter material, i.e., for example, sinter material containing silver or/and platinum, is used in the manner described below. The PTC component 20 is coated with free-flowing, for example, pasty sinter material 28, 30 on its two sides 24, 26, which are oriented such that the two sides 24, 26 face away from one another and are each to be connected to one of the respective carriers 14, 16. This may be carried out, for example, in a screen printing process or with the use of a doctor blade or of such a tool, so that the entire side 24, 26 to be connected to one of the carriers 14, 16 is coated essentially with the sinter material 28, 30.
Each of the two carriers 14, 16 is likewise coated with sinter material 36, 38 on its carrier side 32, 34 that is to be positioned such that it faces the PTC component 20 and is to be connected thereto. A PTC component connection surface area V shown in conjunction with the carrier 14 in
In order to establish a connection between the sinter material 36, 36′ provided on the two sides 32, 48 and 34, 50 of the carriers 14, 16, a sintered material connection area 56, which can be seen in
Alternative embodiments for the sintered material connection area 56 are shown in
Each of the two carriers 14, 16 may be configured as shown in
After the PTC component 20 has been coated on its two component sides 24, 26 with the sinter material 28, 30 and the two carriers 14, 16 have been coated with sinter material in their respective PTC component surface area V, in their contact field surface area K and in the area connecting these two surface areas, the frame 18 can be connected permanently, for example, to one of the two carriers 14, 16, for example, by bonding or the like in the part of the respective edge area 40, 42 which is not coated with the sinter material 36, 38. The PTC component 20 coated with the sinter material 28, 30 on its two sides 24, 26 can then be placed onto this carrier/frame assembly and inserted into the opening 22 of the frame 18, so that the PTC component 20 with the sinter material 28, 30 provided on one of its two sides comes into contact with the sinter material 36 or 38 provided in the PTC component connection surface area V on the carrier 14 or 16 already connected to the frame 18. The other of the two carriers 14, 16 is then put on such that the sandwich-like assembly shown in
After achieving this sandwich-like (sandwich) layering of the two carriers 14, 16 and of the PTC component 20 enclosed by the frame 18, the sinter material 36, 36′, 36″ and 38 is sintered by heating to form the sintered material 36, 36′, 36″ and 38 . A pressure supporting the sintering process may optionally be applied, for example, by loading the two carriers 14, 16 towards one another. It is sufficient due to the advantageous use of sinter material containing silver or/and platinum if heating to a temperature in the range of about 250° C. is carried out during the performance of the sintering process. This ensures, on the one hand, that the respective sinter material 36, 36′, 36″, 38, 28, 30 provided on the carriers 14, 16 and on the PTC component 20 will form a stable connection, but it does, on the other hand, also avoid a structural transformation as the sinter material is sintered to form sintered material. Such a structural transformation is caused by excessive heating and possibly compromises the functionality of the PTC component 20, in the interior of the PTC component 20.
After carrying out the sintering process and after cooling the PTC heating element 10 thus manufactured, a gap-like (gap) intermediate space that may possibly still be present between one or both of the carriers 14, 16, on the one hand, and the frame 18, on the other hand, may be sealed, for example, if the PTC heating element 10 will be used in conjunction with a liquid that is to be heated.
The above-described process for manufacturing the PTC heating element leads in a process, which can be carried out in a simple manner, to a configuration of the PTC heating element 10, which has a simple structure, and in which only a comparatively thin coating with sintered material is to be provided for establishing the mechanical connection and the electrically conductive connection between the PTC component and the two carriers 14, 16 to be provided on this. The thickness of this coating may be about 10 μm, so that the total thickness of the layer of sintered material establishing the connection is also comparatively thin even if such a coating with sintered material 36, 28 and 38, 30 is provided on each of the carriers 14, 16 and on the respective associated side 24, 26 of the PTC component 20. The carriers 14, 16, which are preferably made of a ceramic material, are also good heat conductors contributing to a high efficiency.
Another essential advantage of the PTC heating element 10 manufactured with the procedure according to the present invention is that, as is shown in
It should be noted that different variations are also possible in the above-described procedure for manufacturing a PTC heating element. It is thus possible, for example, that a plurality of PTC components are arranged between two carriers with the above-described procedure. For example, the frame may have for this purpose an opening receiving the PTC component in association with each PTC component to be provided between the two carriers. Further, provisions could be made for the two contact fields to be provided for establishing an electrical contacting of the PTC component to be provided at one of the two carriers, while no such contact field is present at the other carrier. For example, the two contact fields could be provided on the short sides of one of the two carriers configured with a rectangular circumferential contour, which said short sides are located at spaced locations from one another. In order to avoid now an electrical short circuit through the sintered material (already sintered material) providing such contact fields at one of the two carriers, this sintered material (already sintered material) may have an interruption in a length area between the two contact fields in the PTC component connection surface area, so that a flow of current through the PTC component is forced. In another alternative procedure, it would be possible, for example, to make provisions for a coating with sintered material to be carried out only in the area of the carriers, and for the PTC component to be connected to this to be then placed during the sintering process on the sinter material provided on the carrier with its side that is to be positioned such that it faces a respective carrier.
While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.
Number | Date | Country | Kind |
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10 2020 120 472.8 | Aug 2020 | DE | national |