PTC Heating Element And Electric Heating Device With Such A PTC Heating Element And Method For The Production Of A PTC Heating Element

Abstract

A PTC heating element has a casing that joins as a unit at least one PTC element, conductor paths electrically connected to the PTC element, and insulating layers bearing, in a heat-conductive manner against the PTC element. The PTC heating element also has contact strips which project over itself and which are electrically conductively connected to the conductor paths for energizing the PTC element with different polarities. The casing forms a receptacle space that receives the PTC element, the conductor paths, and the insulating layers. In order to improve heat decoupling from the PTC element, the receptacle, in a cross-sectional view, is defined by two oppositely disposed inner surfaces covering the PTC element and concave cavities, adjoining the inner surfaces and forming the longitudinal edges of the casing, the diameter of which is greater than the distance between the inner surfaces. The electric heating device has at least one PTC heating element arranged in a circulation chamber. Also disclosed is a method in which the casing is first formed, the PTC element, the conductor paths and the insulating layers are then introduced through an opening of the casing into the receptacle space, and the casing then is deformed by deforming forces acting upon edge regions of the casing, so that oppositely disposed inner surfaces of the casing are abutted against the insulating layers.

Claims

1. A PTC heating element for an electric heating device, comprising: a casing that joins, as a unit, at least one PTC element, conductor paths that are electrically connected to the PTC element, and insulating layers that bear against the PTC element in a heat-conductive manner; and contact strips which project over the PTC element and which are electrically conductively connected to the conductor paths for energizing the PTC element with different polarities, wherein the casing forms a receptacle space that receives the PTC element, the conductor paths, and the insulating layers, wherein the receptacle space, in a cross-sectional view, is defined by two oppositely disposed flat inner surfaces covering the PTC element, deformation segments adjoining the inner surfaces, and outer longitudinal edges of the casing, wherein the deformation segments are provided, in a cross-sectional view, between one of the inner surfaces and the associated outer longitudinal edge, and wherein the deformation segments are plastically deformed in the direction towards the receptacle space and opposite the inner surfaces and the outer longitudinal edges of the casing.

2. The PTC heating element according to claim 1, wherein the casing comprises at least one reinforcement that holds at least two of the PTC element, the conductor path, and the insulating layer in a prestressed manner in abutment against each other in the casing.

3. The PTC heating element according to claim 2, wherein the reinforcement is formed by a spherical configuration of oppositely disposed main side walls of the casing, the inner surfaces of which, in a cross-sectional view of the casing, are flat and bear against the PTC element and which are thicker at the center of the PTC element than at the edge of the PTC element.

4. The PTC heating element according to claim 1, further comprising a ground connection strip electrically connected to the casing.

5. The PTC heating element according to claim 1, further comprising a seal element that is made of a resiliently soft plastic material, that seals an opening of the casing, and that has contact strips projecting over the deep drawn part.

6. The PTC heating element according to claim 5, wherein the seal element projects over the casing in the direction of the longitudinal extension of the contact strips.

7. The PTC heating element according to claim 5, wherein the casing forms a holding edge holding the seal element.

8. The PTC heating element according to claim 5, further comprising a passage element which is made of an electrically insulating material, which is inserted in the manner of a plug into a free end of the casing t that is penetrated by the contact strips, and which forms passage channels for the contact strips.

9. The PTC heating element according to claim 1, wherein the casing comprises a deep drawn part.

10. The PTC heating element according claim 9, wherein a holding rib is provided opposite to the contact strips and is formed by the deep drawn part.

11. A PTC heating element for an electric heating device, comprising: a casing that joins, as a unit, at least one PTC element, conductor paths that are electrically connected to the PTC element, and insulating layers that bear against the PTC element in a heat-conductive manner; and contact strips which project over the PTC element and which are electrically conductively connected to the conductor paths for energizing the PTC element with different polarities; wherein the casing comprises at least one reinforcement that holds at least two of PTC element, conductor path, and insulating layer in a prestressed manner in abutment against each other in the casing.

12. The PTC heating element according to claim 11, wherein the casing forms a receptacle space that receives the PTC element, the conductor paths, and the insulating layers, wherein the receptacle space, in a cross-sectional view, is defined by two oppositely disposed flat inner surfaces covering the PTC element, deformation segments adjoining the inner surfaces, and outer longitudinal edges of the casing, and wherein the deformation segments are provided, in a cross-sectional view, between one of the inner surfaces and the associated outer longitudinal edge, and wherein the deformation segments are plastically deformed in the direction towards the receptacle space and opposite the inner surfaces and the outer longitudinal edges of the casing.

13. An electric heating device comprising: at least one PTC heating element arranged in a circulation chamber, the PTC heating element including a casing that joins, as a unit, at least one PTC element, conductor paths that are electrically connected to the PTC element, and insulating layers that bear against the PTC element in a heat-conductive manner, wherein the casing has contact strips which project over itself and which are electrically conductively connected to the conductor paths for energizing the PTC element with different polarities, wherein the casing forms a receptacle space that receives the PTC element, the conductor paths, and the insulating layers, wherein the receptacle space, in a cross-sectional view, is defined by two oppositely disposed flat inner surfaces covering the PTC element, deformation segments adjoining the inner surfaces, and outer longitudinal edges of the casing, wherein the deformation segments are provided, in a cross-sectional view, between one of the inner surfaces and the associated outer longitudinal edge, and wherein the deformation segments are plastically deformed in the direction towards the receptacle space and opposite the inner surfaces and the outer longitudinal edges of the casing.

14. A method for the production of a PTC heating element for an electric heating device that includes a casing that joins, as a unit, at least one PTC element, conductor paths that are electrically connected to the PTC element, and insulating layers that bear against the PTC element in a heat conductive manner, and that includes contact strips which project over the PTC element and which are electrically conductively connected to the conductor paths for energizing the PTC element with different polarities, the method comprising: introducing the PTC element, the conductor path, and the insulating layers through an opening of the casing part into a receptacle space formed by the casing part, and then deforming the casing part by deforming forces acting upon edge regions of the casing part, so that oppositely disposed inner surfaces of the casing part are abutted against the insulating layers.

15. The method according to claim 14, wherein the deforming forces act exclusively on an edge of the casing which is located outside of a projection surface of the main side surfaces of the PTC element to be abutted against the insulating layers on an inner surface of the casing.

16. The method according to claim 14, wherein the deforming forces are applied by a die with an upper and a lower part, forming surfaces of which interact with the outer side of the casing outside the PTC element, and wherein the oppositely disposed longitudinal edges of the casing in the die are enclosed in the direction of motion of the die on the upper and lower side and at right angles thereto.

17. The method according to claim 14, wherein the casing is formed by deep drawing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Further details and advantages of the present invention shall become apparent from the following description of an embodiment in combination with the drawing, in which:

[0038] FIG. 1 shows a perspective side view of an embodiment of an electric heating device;

[0039] FIG. 2 shows a perspective side view of the embodiment according to FIG. 1 after connection of the PTC heating elements;

[0040] FIG. 3 shows a perspective explosion view of the PTC heating element of the electric heating device shown in FIGS. 1 and 2;

[0041] FIG. 4 shows a perspective side view of the embodiment of a PTC heating element illustrated in FIG. 3;

[0042] FIG. 5 shows a perspective longitudinal sectional view taken along line V-V according to the illustration in FIG. 4 before the PTC heating element is pressed together;

[0043] FIG. 6 shows a perspective cross-sectional view taken along line VI-VI according to the illustration in FIG. 4 before the PTC heating element is pressed together;

[0044] FIG. 7 shows a perspective longitudinal sectional view taken along line V-V according to the illustration in FIG. 4 after the PTC heating element has been pressed together;

[0045] FIG. 8 shows a perspective cross-sectional view taken along line VI-VI according to the illustration in FIG. 4 after the PTC heating element has been pressed together;

[0046] FIG. 9 shows a cross-sectional view of the embodiment of the PTC heating element according to FIGS. 3 to 8 when being pressed together in a die.

DETAILED DESCRIPTION

[0047] FIG. 1 shows a perspective top view onto a heater casing marked with reference numeral 2 of an electric heating device formed as a water heater. The heater casing 2 has a casing tub element 4 made of plastic material. The heater 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.

[0048] 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 and supported on a base 24 of the casing tub element 4.

[0049] FIGS. 3 to 9 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 layers 34 are presently formed from a plastic film, for example made of Kapton. The PTC element 30 is configured as a platelet having a width B or a length L, respectively, that is greater by the factor of at least 10 than a thickness that corresponds to the distance between the two main side surfaces 32.

[0050] Provided on oppositely disposed main side surfaces 32 are respective contact plates 38 which can be adhesively bonded to the PTC element 30 and thereby be 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 contact plates 38 can also only merely be placed onto the PTC element 30. Each contact plate 38 forms a contact surface 40 which is abutted in an electrically conductive manner against the main side surface 32 of the PTC element 30, a contact strip 42 projecting on one side above the PTC element 30, and a snap-on spade 44 projecting at the opposite side, hereafter referred to as the underside. The contact surface 40 is presently provided coinciding with the main side surface 32 of the PTC element 30. The insulating layer 34 lies on the side facing away from the PTC element 30 on the contact plate 38 and covers the latter.

[0051] The PTC element 30 is received in a frame 46 which for this purpose comprises a frame opening 48 which is defined by longitudinal tie members 50 and cross tie members 52, 54. The lower cross tie member 54 has two locking openings 56 to accommodate the snap-on spades 44. The upper cross tie member 52 is formed integrally with a passage element base 58 which together with a passage segment lid 60 forms a kind of plug over which a stop collar 61 projects. Projecting over this stop collar 61 are half shells 62 which is formed by the frame 46 and from which pins 64 protrude. Corresponding thereto, the passage segment lid 60 comprises bores 66 and half shells 68 that are aligned with them.

[0052] For assembly, one of the contact plates 38 is first placed with its contact strip 44 into the half shell 62. The pin 64 is there passed through a bore recessed on the contact strip 44. The snap-on spade 44 of the contact plate 38 is introduced into the associated locking opening 56. Connected in this manner, the frame 46 has a base formed by the contact plate 38 onto which the PTC element 30 is placed. Thereafter, the further contact plate 38 is placed in the manner previously described into the other of the two half shells 62 and onto the main side surface 32 of the PTC element 30.

[0053] The passage segment lid 60 is mounted thereafter, so that the pins 64 are inserted into the bores 66 and the half shells 68 of the lid 60 complete the half shells 62 of the base 58. Thereafter, the respective contact strips 42 are received in an insulating manner in a passage channel 70 respectively formed by the half shells 62, 68 and extended beyond the frame 46 (compare FIG. 4). The pins 64 can then undergo staking to captively connect base 58 and lid 60 to each other.

[0054] The structural unit thus produced is covered with insulating layer 34. For this purpose, the plastic film forming the insulating layer 34 is folded over at the lower end of the frame around the lower cross tie member 54, so that parallel legs result which are each formed by the uniform film and form the insulating layers 34.

[0055] The unit thus produced is inserted into a casing 72 which is presently formed from sheet metal by deep drawing and provided with a single opening 74, where the region of casing 72 disposed opposite the opening 74 is closed and provided with a holding rib 76 which interacts in a receiving groove recessed on the base 24 of the heater casing 2 for positioning the PTC heating element 22 in the heater casing 2. The pre-assembled unit is introduced through the opening 74 into a receptacle space 78 of the deep drawn part 72. At the end of the insertion motion, the stop collar 61 abuts against the edge of the opening 74, thereby predetermining the mounting position of the frame 46 and thus of the components of the PTC heating element 22 held by the frame 46 and placed around the frame 46.

[0056] Below the opening 74, the deep drawn part 72 forms a holding edge 80 which circles circumferentially parallel to the edge of the opening 74 around the deep drawn part 72 and between itself and the opening 74 forms a collar 82 that forms a bearing surface for a seal element 84. The seal element 84 is made of a resiliently soft plastic material, for example TPE or silicone, and has passage openings 86 for the half shells, 62, 68 connected to each other. The seal element 84 can be produced separately and joined with the frame 46 and the deep drawn part 72. Alternatively, it is also possible to connect the seal element 84 by overmolding it with the frame 46 and the deep drawn part 72.

[0057] The seal element 84 is in any case supported on the holding edge 80 which is formed by the deep-drawn part 72 itself and shaped by deep drawing the sheet material. All contours and projections provided on the deep drawn part 72 are realized by the deep drawing and a result of the forming processing of the sheet metal. Only the opening 74 is formed by cutting off the excess sheet metal material and optional deburring.

[0058] As FIG. 4 shows, the contact strips 44 project over the free ends of the joined half shells 62, 68 and can be used as male plug elements of a plug connection to the PTC heating element 22. Disposed at a distance to the face side of the joined half shells, 62, 68 is the seal element 84.

[0059] The economical introduction of the elements previously mentioned into the receptacle space 78 entails that the insulating layers 34 initially do not bear against the associated inner surfaces of the receptacle space 78 in a sufficiently heat-conductive manner, which

[0060] FIGS. 5 and 6 illustrate. After the assembly of the components, the deep drawn part 72 is then deformed in the region of its longitudinal edges 88. The deep drawn part 72 is for this purpose introduced into a die 90 with upper part 92 and lower part 94 which are basically formed in an identical manner.

[0061] FIG. 9 indicates that the two parts 92, 94 each form a deformation edge 96 which is abutted against the outer surface of the deep drawn part 72. The point of attack of the deformation edge 96 in the sectional view is located sideways next to the transverse extension of the PTC element 30 and the associated contact plates 40. The deformation edge 96 engages in a free space which is left exposed between the associated longitudinal tie member 50 and the PTC element 30 or the contact surface 40, respectively, and is bridged only by the insulating layer 34 which at least in part projects over the respective longitudinal tie member 50.

[0062] The deep drawn part 72 is then deformed only in the region of its longitudinal edges 88. The curvature of the longitudinal edges 88 of the deep drawn part 72 produced by deep drawing and initially basically formed in a semicircular manner are bent more inwardly whereby the inner surfaces of the deep drawn part extending parallel to the main side surfaces 32 are abutted under prestress against the surfaces of the insulating layers 34.

[0063] The die 90 takes hold of the respective longitudinal edges 88 both in the direction of motion of the two parts 92, 94 toward each other, as well as at the outer side of the deep drawn part 72. The deep drawn part 72 inserted into the die 90 with its exterior outer sides defined by the longitudinal edges 88 contacts the die 90. The metallic material of the deep drawn part 72 can accordingly only be deformed in the direction toward the PTC element 30.

[0064] The deformation edge 96 does not act directly against the PTC element 30, so that damage thereto during the forming process is avoided to the extent possible. In addition, after the forming process, a resilient prestress arises, which results in reliable heat dissipation due to good heat conduction from the PTC element 30 through the contact plates 40 and the insulating layer 34 to the inner surface of the deep drawn part 62 and through the latter by way of heat conduction to the outside.

[0065] The deep drawn part 72 with its main side surface is evidently formed as a sphere. An inner surface 98 extends flush with the main side surface 32 of the PTC element 30, whereas the outer side of the deep drawn part 72 disposed opposite to the main side surface 32 is formed in a convex manner. Accordingly, in a cross-sectional view, the deep drawn part 72 has a greater thickness at the center of the inner surface 98 than at the edge of the inner surface 88. This configuration improves the prestress and strength of the deep drawn part 72 for applying an external pressing force of the elements of the PTC heating element 22 mounted in the receptacle space 78.

[0066] The flat inner surface 98 of the deep drawn part 72 respectively transitions at the edge to a cavity having essentially the shape of a segment of a circle. The deformation previously mentioned of the deep drawn part 72 takes place only in the region of this cavity. The C-shaped claw, still open in FIG. 6 and formed by the cavity, is more clearly seen clearly more closed after the forming processing and in FIG. 8. In other words, the diameter of each cavity of the deep drawn part 72 provided at the longitudinal edges of the deep drawn part 72 is reduced by forming processing, whereby the inner surfaces 98 disposed opposite to each are abutted toward each other and under prestress against the insulating layer 34.

[0067] Specifically, a deformation segment 99 is formed through the casing respectively between an outer longitudinal edge 97 and the inner surface 98. This deformation segment 99 is plastically deformed in the direction toward the receptacle space 78. Four such deformation segments 99 are provided in the embodiment shown. Two deformation segments 99 are provided between the inner surface 98 and the outer longitudinal edge 97 on the upper side as well as on the lower side according to FIG. 8. However, for the inner surfaces 98 bearing against the PTC element 30 in a prestressed manner, it is sufficient to provide and plastically deform the corresponding deformation segments 99, for example, only on the upper side in order to introduce an internal prestressing force into the casing. Where it is irrelevant whether the casing is produced by deep drawing or otherwise. When deforming the deformation segments 99, the outer longitudinal edge 97 presently remains undeformed.

[0068] As the comparison of FIGS. 5 and 6 with FIGS. 7 and 8 shows, the inner surface 98 of the deep drawn part 62 bears flush against the insulating layer 34 after the deformation according to FIG. 9.

[0069] FIG. 2 illustrates the electrical connection of the PTC heating elements 22. For the electric connection, pieces of punched sheet metal are provided in the connection chamber 18 as current bars 100, 102, 104, comprising contact projections 106 formed by punching and bending which bear against the contact strips 42 subject to resilient prestress and contact them. The contact projections 106 project into receptacle openings 108 which are recessed in the sheet metal strips of the current bars 100, 102, 104. Connection strips marked with reference numeral 110 are connected in the same way and are contacted to a fitted circuit board which is accommodated in a control casing 112. The connection of the current bar 102 is established directly via the connection strip 110, whereas the connection of the current bars 100, 102 is established via a power transistor 114 which is contacted by punched conductors 116 which are electrically connected to the associated connection strips 110.