PTC heating element and electric heating device comprising such

Abstract

A PTC heating element for an electric heating device includes frame which is made of electrically non-conductive material and which encloses at least one PTC element, conductor tracks electrically connected to the PTC element, and insulating layers bearing, in a heat-conductive manner, against an oppositely disposed main side surface of the PTC element. The frame has contact strips which project over itself and which are electrically conductively connected to the conductor tracks for energizing the PTC element with different polarities. In order to provide an electrically well-insulated PTC heating element allows good heat coupling, s a film respectively covers the outer surfaces of the insulating layers. A corresponding PTC heating element may be provided in a circulation chamber of the electric heating device. In this case, the conductor tracks are electrically connected to the PTC element, protrude through a partition wall of the electric heating device, and are exposed and electrically connected in a connection chamber. The connection chamber is separated by the partition wall from the circulation chamber.

Claims

1. A PTC heating element for an electric heating device comprises: a frame which is made of an electrically non-conductive material and which encloses at least one PTC element, conductor tracks which are electrically connected to the PTC element, and insulating layers bearing, in a heat-conductive manner, against oppositely disposed main side surface of the PTC element, wherein the frame has contact strips projecting over itself which are electrically conductively connected to the conductor tracks for energizing the PTC element with different polarities, and wherein a film covers the outer surfaces of the insulating layers.

2. The PCT heating element according to claim 1, wherein the frame and the film are formed as a structural unit.

3. The PTC heating element according to claim 2, wherein the frame and the film are formed by injection molding an electrically insulating plastic material around the PTC element, the insulating layers, and the conductor tracks.

4. The PTC heating element according to claim 1, wherein the frame comprises the insulating layer and frame struts which circumferentially surround the PTC element and which project over the film in a thickness direction of the PTC heating element outwardly on both sides.

5. The PTC heating element according to claim 1, wherein the frame and the film are formed from silicone.

6. The PTC heating element according to claim 5, wherein the film is connected in a positive substance-fit manner to the insulating layer.

7. The PTC heating element according to claim 3, wherein a core is provided which made of electrically insulating material, through which the contact strips protrude, and which is received in the frame.

8. The PTC heating element according to claim 1, further comprising an electromagnetic shielding which is formed from a metal structure, which is permeable to fluid, and which surrounds the PTC element and the conductor track.

9. The PTC heating element according to claim 8, further comprising at least one shielding connection lug that is connected in an electrically conductive manner to the shielding, that extends parallel to the contact strips, and that projects over the shielding.

10. A PTC heating element for an electric heating device, comprising: a frame which is made of electrically non-conductive material and which encloses at least one PTC element, conductor tracks which are electrically connected to the PTC element, and insulating layers which bear, in a heat-conductive manner, against oppositely disposed main side surface of the PTC element, wherein the frame has contact strips which project over itself and which are electrically conductively connected to the conductor tracks for energizing the PTC element with different polarities, further comprising a film respectively covering the outer surfaces of the insulating layers, wherein the frame and the film are formed by injection molding an electrically insulating plastic material around the PTC element, the insulating layers, and the conductor tracks, and further comprising 1) an electromagnetic shielding that is formed from a metal structure, that is permeable to fluid, and that surrounds the PTC element and the conductor track, and 2) at least one shielding connection lug which is connected in an electrically conductive manner to the shielding and which extends parallel to the contact strips and projects over the shielding.

11. The PTC heating element according to claim 10, wherein the frame comprises the insulating layer and frame struts which circumferentially surround the PTC element and which project over the film in a thickness direction of the PTC heating element outwardly on both sides, wherein the frame and the film are formed from silicone, and further comprising a core which is made of electrically insulating material, through which the contact strips protrude, and which is received in the frame, wherein the core is surrounded by the resiliently soft plastic material.

12. The PTC heating element according to claim 11, further comprising 1) an electromagnetic shielding which is formed from a metal structure, which is permeable to fluid, and which surrounds the PTC element and the conductor track, and 2) and at least one shielding connection lug which is connected in an electrically conductive manner to the shielding, which extends parallel to the contact strips, and which projects over the shielding.

13. An electric heating device comprising at least one PTC heating element which is arranged in a circulation chamber, the PTC heating element including a frame which joins at least one PTC element and contact strips as a structural unit, wherein the contact strips energize the PTC element, are electrically connected to the PTC element, and project over itself, and further comprising a partition wall which separates the circulation chamber from a connection chamber in which the contact strips of the PTC element, protruding through the partition wall, are exposed and electrically connected, wherein the PTC heating element comprises a frame which is made of an electrically non-conductive material and which encloses at least one PTC element, conductor tracks which are electrically connected to the PTC element, and insulating layers bearing, in a heat-conductive manner, against oppositely disposed main side surface of the PTC element, wherein a film covers the outer surfaces of the insulating layers.

14. The electric heating device according to claim 13, wherein that the PTC heating element is inserted into the partition wall in a sealing manner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further details and advantages of the present invention shall become apparent from the following description of embodiments in combination with the drawing, in which:

(2) FIG. 1 shows a perspective side view of an embodiment of an electric heating device;

(3) FIG. 2 shows a perspective side view of the embodiment according to FIG. 1 after connection of the PTC heating elements;

(4) FIG. 3 shows a perspective side view of parts of a PTC heating element;

(5) FIG. 4 shows a partially broken perspective side view of the PTC heating element;

(6) FIG. 5 shows a perspective cross-sectional view of the PTC heating element;

(7) FIG. 6 shows a perspective and partially cut side view of a second embodiment of a PTC heating element;

(8) FIG. 7 shows detail VII according to FIG. 6 in an enlarged representation and

(9) FIG. 8 shows a sectional view taken along line VIII-VIII according to FIG. 6.

DETAILED DESCRIPTION

(10) FIG. 1 shows a perspective top view of a casing, designated by reference numeral 2, of an electric heating device configured as a water heater. The heater casing 2 has a casing tub element 4 made of plastic material. The casing 2 forms an inlet port 6 and an outlet port 8 which are presently embodied formed integrally on the casing tub element 4. The ports 6, 8 are designed as hose connection ports and form an inlet opening 10 and an outlet opening 12, respectively, to a circulation chamber designated with reference numeral 14.

(11) The circulation chamber 14 is separated from a connection chamber 18 and sealed thereagainst by a partition wall 16 made of plastic material. The partition wall 16 forms female plug element holding fixtures 20 for PTC heating elements 22 which are inserted into the female plug element holding fixtures 20 in a sealed manner and supported on a base 24 of the casing tub element 4.

(12) FIGS. 3 to 5 illustrate details of the PTC heating element 22 which presently comprises only one PTC element 30 which at its oppositely disposed main side surfaces 32 is covered with an insulating layer 34. The insulating layer 34 is presently a ceramic plate made of aluminum oxide. However, it can also be applied as a coating onto the PTC element 30 or as a combination of a coating with a single or multiple layer insulation coat. The PTC element 30 is designed as a platelet having a width B or a length L, respectively, that is greater by the factor of at least 10 than the thickness D which corresponds to the distance between the two main side surfaces 32. Sheet metal strips 38 substantially extending in the direction of the length L are provided on mutually oppositely disposed face side surfaces 36 and are glued to the PTC element 30 and are connected in an electrically conductive manner to a surface metallization of the PTC element 30 which can be applied as a layer by way of PVD or CVD. The sheet metal strips 38 consist of a contact ridge 40 which is relatively narrow and the contact strip 42 which is widened in relation to the contact ridge 40 in the direction of the width B.

(13) The contact ridges 40 presently form the conductor tracks to the PTC element 30 and are electrically connected to the metallization of the PTC element 30. The sheet metal strip 38 is provided such that it does not project over the main side surfaces 32 of the PTC element 30 at any point. As can be seen in FIGS. 4 and 5, the insulating layers 34 project laterally over the PTC element 30. The insulating layers 34 accordingly have a base area which is larger than the base area of the main side surfaces 32 of the PTC element 30. Accordingly, the outer edges of the insulating layers 34 receive the contact ridge 40 between themselves on both sides (see FIG. 5). The insulating layer 34 is glued to the PTC element 30. The insulating layer 34 bears directly onto the PTC element. One of the insulating layers 34 therefore directly contacts the associated main side surface 32 of the PTC element 30.

(14) Alternatively, the sheet metal strip 38 can be applied according to the invention entirely or in part as a contact plate flat on the main side surface 32. With regard to good heat decoupling perpendicular to the main side surface 32, however, the variant discussed in the context of the embodiment is to be preferred.

(15) The sheet metal strip 38 is largely received in a frame 44 made of insulating material which surrounds the PTC element 30 on all four circumferential sides. The frame 44 has four frame struts 45. This frame 44 circumferentially encloses the circumferential edges of the insulating layers 34. The contact ridges 40 are also encapsulated by the material forming the plastic frame 44. The frame 44 is formed by injection molding around an elastomer material, in particular silicone.

(16) With the completed PTC heating element 22, only the contact strips 42 project over the frame 44 on a face side. All other functional parts of the PTC heating element 22 used for heat generation and current conduction are accommodated within the frame 44. As visualized in particular by FIGS. 4 and 5, the frame 44 integrally forms a film 46 which is provided plane-parallel to the insulating layer 34 and connected thereto in a positive substance-fit manner. The insulating layers 34 provided there are each covered on both main side surfaces by the film 46 over the entire surface. Each film 46 transitions completely to the frame 44. The film 46 has a thickness, i.e. extension perpendicular to the main side surface 32, of no more than 50 microns, preferably no more than 20 microns.

(17) As illustrated in particular by FIG. 5, the PTC element 30, the insulating layer 34, and the film 46 are located behind a frame opening designated with reference numeral 48 and formed by the frame 44. The frame 44, i.e. the frame struts 45, are accordingly thicker than the sum of the thicknesses of PTC element 30, the two insulating layers 34, and the two layers of the film 46.

(18) Almost no overlap of the frame 44 with the main side surfaces 32 of the PTC element 30 presently arises at all so that the latter is located in the frame openings 46 with almost 100% of its main side surfaces 32 covered by the film 46 and the insulating layer 34.

(19) The frame 44 forms a sealing collar 50 which is provided with sealing lips 52 arranged tapering conically toward the free end of the contact strips 42. Three of these sealing lips 52 are presently provided one behind the other in the direction of longitudinal extension of the contact strip 42 as a kind of labyrinth seal. The sealing collar 50 made of the resiliently soft plastic material is injection molded around a core 54 made of an electrically insulating plastic material which comprises passage openings, not shown, for passing the widened regions of the sheet metal strips 38 through and is used for the pre-assembly of the sheet metal strips 38. This core 54 increases the pressing force of the sealing collar 50 during the insertion into the female plug element holding fixture 20.

(20) The sealing collar 50 is defined at the underside by a circumferential annular stop 56 which after insertion of the PTC heating element 22 into the female plug element holding fixture 44 bears in a sealing manner against an abutment bead formed by the partition wall 16.

(21) FIG. 2 illustrates the electrical connection of the PTC heating elements 22. For the electric connection, pieces of sheet metal are provided in the connection chamber 18 as current bars 60, 62, 64, comprising contact projections 66 formed by punching and bending which bear against the contact strips 42 subject to resilient prestress and contact them. The contact projections 66 project into receptacle openings 68 which are recessed in the sheet metal strips of the current bars 60, 62, 64. Connection strips marked with reference numeral 70 are connected in the same way and are contacted to a fitted circuit board which is accommodated in a control casing 72. The connection of the current bar 62 is there established directly via the connection strip 70, whereas the connection of the current bars 60, 64 is established via a power transistor 74 which is contacted by punched conductors 76 which are electrically connected to the associated connection strips 70.

(22) The control casing 72 comprises a connector casing 78 for the power current and a connector casing 80 for the connection of cables for the control signals.

(23) FIGS. 6 to 8 show an alternative embodiment of a PTC heating element. The same components are given the same reference numerals as in to the previously discussed embodiment. The embodiment has a frame 44 which also forms a sealing collar 50 that is formed integrally thereon and that can be inserted into in the casing 2 in a sealing manner as described in DE 10 2016 224 296 A3. As can be seen, the outer surfaces of the plastic material defining the frame 44 has been injected during injection molding around a holding frame 82 which encloses a presently planar metal structure 84 at the edge which forms an electromagnetic shielding. The corresponding holding frame 82 is first connected to the metal structure 84 and placed as an insert member into the injection mold. The holding frame 82 defines the cavity at the inner circumference for the formation of the frame 44.

(24) The contact strips 42 are presently formed by elongated sheet metal strips 38 which at the face side bear against and energize the PTC element 39. The main side surface 32 of the PTC element 30 decoupling the heat on the outer side is covered with the insulating layer 34 and the film 46 which are sealed at the edge into the material of the heating element casing 2.

(25) The sealing collar 50 is penetrated by a contact plate 86 which is made of sheet metal material by punching and bending and forms a contact section 88, protruding on both sides in the direction towards the metal structure 84, which is connected to the metal structure 84 in an electrically conductive manner. By connecting a shielding connection lug 90 formed by the contact plate 86, it is possible to electrically connect the metal structure 84 provided on a main side surface 32 to a shielding pol.

(26) The embodiment shown in FIGS. 6 to 8 has two identically formed contact sections 88 which are each connected to the oppositely disposed main side surfaces 32 to the metal structure 84 provided there as a flat metal fabric and of which only the contact section 88 of the upper side is shown.