PTC heating element and method for its manufacture

Abstract

A PTC heating element with a frame-shaped housing (10) forming a receptacle (15) for at least one PTC element (50), which forms a sealing collar (11) between contact tongues (52) that are electrically connected to contact elements (51) via which the PTC element (50) is electrically contacted, and the PTC element (50), wherein the frame (10) is made of a soft elastic plastic material and the PTC element (50) is covered on the outside of the housing (10) with an insulating layer (57), characterized in that the receptacle (15) is a receptacle (15) adapted for inserting the PTC element (50) and that the receptacle (15) is adapted such that the PTC element (50) is exposed in the receptacle (15) with its opposite main side surfaces.

Description

[0001] The present invention relates to a PTC heating element with a frame-shaped housing that forms a receptacle for at least one PTC element and features a light collar. In the PTC heating element according to the invention and known from EP 3 344 244 A1, the sealing collar is located between contact tongues and the PTC element. The contact tongues serve for the electrical connection of the PTC element by means of plug-in contacts. They are electrically connected to contact elements via which the PTC element is electrically contacted. The frame is made of a soft, elastic plastic material. In the prior art, the PTC heating element is partially formed on the outside of the housing by an insulating layer that covers the PTC element.In this state of the art, insulating layers are connected to the housing by overmolding the plastic material on both sides of the main heat-extracting side surfaces of the PTC element during the manufacture of the frame-shaped housing.

[0002] The sealing collar serves for the sealed insertion into a plug contact receptacle of a superior heater housing, which is described, for example, in the aforementioned prior art and is also suitable for the installation of the PTC heating element according to the present invention.

[0003] However, the PTC heating element known from EP 3 344 244 A1 still leaves something to be desired. Overmolding requires precise process control. If the insulating layer is to be made of a relatively brittle ceramic material, there is a risk of it breaking. Inadequate process control during overmolding of the insulating layer can lead to leakage, allowing moisture to penetrate the housing and render the PTC heating element unusable. The PTC heating element according to the invention is, in particular, a heating element for heating a liquid medium, which, in high-voltage applications, can also cause a short circuit in the event of a leak. There is also a risk to technicians, for example, during the inspection or maintenance of an electrical heating device that incorporates the known PTC heating element.

[0004] The present invention specifically aims to provide a PTC heating element for an electric heating device in a motor vehicle. In this respect, the present invention does not differ in its applicability from the application described in EP 3 344 244 A1.

[0005] The present invention aims to provide a PTC heating element which is easier to manufacture with higher process reliability.

[0006] To solve this problem, the present invention provides a PTC heating element with the features of claim 1. This differs from the previously known PTC heating element in that the receptacle for inserting the PTC element is adapted. While in the prior art the PTC element is necessarily received in the housing after the two insulating layers have been connected to the housing, the design of the PTC heating element according to the invention allows the PTC element to be inserted into the previously formed receptacle later. The PTC element can be inserted into the receptacle in such a way that its opposing main side faces are exposed within the receptacle.

[0007] The main faces of the PTC element are those surfaces, usually opposite each other, that have the largest surface area. Typically, the PTC element is a cuboid with significantly larger opposing main faces than boundary faces. These boundary faces completely surround and connect the main faces, each perpendicular to the other and to the main faces.

[0008] The metallization is usually applied to these main side surfaces. Current is typically supplied via these main side surfaces. However, in the PTC heating element according to the invention, current can also be supplied according to the PTC heating element of EP 3 344 244 A1, namely via opposing end faces that extend perpendicular to the main side surfaces and connect them. In this case, the metallization applied to the semiconductor stone is located at least on the respective end faces. The combination of semiconductor stone and the metallization directly applied to it, i.e., vapor-deposited or sputtered, is regularly understood as a PTC element within the meaning of the present invention.

[0009] The solution proposed by the present invention offers the advantage that the housing can be manufactured from a single material and thus cost-effectively. The soft-elastic plastic material has sufficient rigidity to define a receptacle. However, it is also soft enough to provide, for example, an elastic sealing surface in the area of ​​the sealing collar, which can be inserted into a receptacle formed on a heater housing and sealed by means of a plug connection. A soft-elastic plastic material within the meaning of the present invention is, in particular, one with a Shore A hardness of between 50 and 90, preferably between 50 and 70. The plastic material is preferably selected from the group consisting of NBR, HNBR, EPDM, and silicone.The plastic material is preferably a thermoplastic or thermoplastic elastomer, which can be processed by injection molding and thus manufactured cost-effectively as a mass-produced product.

[0010] The housing is preferably designed as a single, unified body. This unified body preferably forms all sealing elements for sealing the PTC heating element when inserted into a heater housing and also seals the receptacle, so that the PTC element is securely held in the receptacle. According to a preferred embodiment of the present invention, the housing forms a sealing bead surrounding the receptacle. This sealing bead is preferably located on one, and more preferably on both, main side surfaces of the housing that surround the receptacle. A cover can be placed on this sealing bead to close the receptacle. However, it is preferable to first apply an insulating layer to the edges of the housing surrounding the receptacle. This insulating layer preferably also serves to seal the receptacle. For this purpose, the insulating layer is preferably completely surrounded by the aforementioned sealing bead.By adding a further cover element, which will be described in more detail below, the sealing bead can be compressed and thus also pressed against the outer circumferential surface of the insulating layer. This increases the seal. The sealing bead can press against the insulating layer on its end face and also on its top face. According to a preferred embodiment of the present invention, this insulating layer lies directly against the edges of the housing surrounding the receptacle, creating a seal under preload. This preload is typically applied externally, which will be explained in more detail below. With this design, the insulating layer is sealed against the housing due to its flat contact with the main surface. An additional seal of the insulating layer is preferably provided circumferentially by the aforementioned sealing bead.

[0011] The present invention provides various measures that ensure a secure and permanent seal of the mounting during operation. This seal is particularly important when using the PTC heating element in an electric heating device for a motor vehicle, since vibrations and significant temperature fluctuations occur in a motor vehicle, placing special demands on the quality of every seal and mechanical connection within the vehicle. This applies especially to elements of an electric heating device that are operated with high-voltage current, namely the PTC element, provided it is installed and operated in an electric vehicle with the operating voltage of at least 40 volts. The PTC element according to the invention is suitable for operation in both a low-voltage range up to 60 volts and a high-voltage range up to 800 volts.

[0012] Preferably, the PTC heating element of the present invention has at least one housing shell element that at least partially surrounds the housing. The housing shell element can have a U-shaped cross-section, such that it has surface elements that are parallel to the main surface and cover the receptacle and the underlying insulating layer. The housing element is designed to abut the edges surrounding the receptacle, preferably the aforementioned sealing bead. The housing shell element according to the present invention can be formed as a flat sheet. By bearing against the housing, the housing shell element provides the housing with sufficient rigidity. By bearing against the housing shell element, the main side surfaces are aligned parallel to the housing shell element. The housing shell element is typically made of a sheet material, for example, AlMg3.Since the housing shell element rests against the main side of the housing at least on one side, preferably on both sides, good thermal conductivity must be ensured.

[0013] The at least one housing shell element also serves to seal the receptacle. For this purpose, the at least one housing shell element abuts the housing, preferably the edges of the housing surrounding the receptacle, in a sealing manner. A circumferential sealing bead is preferably provided there, which surrounds the receptacle and interacts with the at least one housing shell element. The insulating layer can be provided as described above, completely surrounded by the sealing bead and applied abutting the edges of the housing. For the sake of simpler assembly, it may be preferable to make the insulating layer smaller so that it can be arranged within the receptacle without protruding beyond it and abutting one or all of the edges of the housing surrounding the receptacle.In the preferred embodiment discussed last, the insulating layer, together with the contact elements and the PTC element, can be arranged as a prefabricated unit in the fixture. This design reduces the number of process steps. Furthermore, the aforementioned layers of the PTC heating element can also be pressed against each other and bonded during pre-assembly, thereby improving heat conduction between the PTC element and the outer surface of the heat-generating layered unit consisting of the PTC element, the contact elements, and the insulating layers. For the embodiment of the present invention, it is not necessary for the contact elements between the insulating layer and the PTC element to be arranged such that the PTC element is on one side and the insulating layer on the other side of each contact element.Rather, contact elements can also be provided against the edge surfaces of the PTC element and between opposing insulating layers.

[0014] Alternatively, the PTC element can also be designed as a pre-assembled unit with only one of the contact elements and, optionally, a single-sided insulating layer assigned to the respective contact element, preferably in conjunction with a connector holder that serves to position the individual elements of the heat-generating cell. This pre-assembled unit, whose elements are preferably bonded together, can then be inserted into the receptacle before the other of the two contact elements and, optionally, the additional insulating layer are mounted to complete the heat-generating unit and mechanically joined by the at least one housing shell element, preferably by the clamping element interacting with it.

[0015] The housing shell element can have a central recess so that the insulating layer comes into direct contact with the medium to be heated. However, the recess is dimensioned such that the housing shell element completely covers the sealing bead and thus seals the receptacle.

[0016] The housing shell element is preferably bent, so that angled edges project from a base surface adjacent to the main side of the housing. These edges preferably extend beyond and define the outer circumference of the housing's surrounding leg, thus providing a form- and / or contour-defining fit for the initially not very rigid, plastic housing within the housing shell element. After the housing shell element is in place, the PTC heating element achieves sufficient rigidity and geometric alignment through the combination of the soft, elastic plastic material and the rigid housing shell element. In this respect, it is also preferable to position an edge of the housing shell element directly against the sealing collar, so that the sealing collar is also positioned relative to the orientation of the housing shell element.Furthermore, the bent edges give the initially flat sheet metal material of the housing shell element sufficient inherent rigidity.

[0017] The housing shell element preferably rests directly against the main surface of the housing. Furthermore, the housing shell element is preferably applied under preload against the insulating layer, which in turn is typically in contact with the PTC element via an interposed contact element. Accordingly, the housing shell element, through its elastic contact against the insulating layer, ensures electrical and / or thermal contact between the contact element and the PTC element, as well as efficient heat dissipation from the PTC element through the insulating layer and the housing shell element to the outside of the PTC heating element. This is because the housing shell element preferably lies exposed on the outside of the PTC heating element and thus forms the outer surface of the PTC heating element, i.e., the outer surface for dissipating the heat generated inside.

[0018] The housing shell element preferably acts mechanically on the sealing bead and usually rests against it, causing it to deform and possibly be pressed against the adjacent geometry of the insulating layer to reliably seal the recess.

[0019] For reasons of economical manufacturing, it is preferable to attach two identically designed housing shell elements to opposite main sides of the housing. The housing shell elements have corresponding edges that completely surround and encapsulate the housing in the area of ​​the legs surrounding the receiver. The housing shell elements abut each other in the area of ​​the edges or are spaced apart from each other with minimal clearance. The housing shell elements thus define an interior space that encloses the legs of the housing and preferably supports them directly by contacting the legs, preferably all legs.

[0020] Although the previously described contacting of the PTC element should take place via its main side surface by placing the contact element against it, an end-face contacting is also conceivable, in which the contact element rests against the PTC element at an edge side, especially if the housing shell element also rests against the outer circumferential surfaces of the legs under preload and this preload force is transmitted through the elastic legs to the phase boundary between the contact element and the PTC element.

[0021] According to the present invention, the contact between the contact element and the PTC element does not necessarily have to be achieved solely by a preload force. Rather, the contact elements can be joined to the PTC element by gluing, soldering, or other material-bonded connection methods. The externally applied preload force helps in any case to secure and improve the corresponding connection. Furthermore, contact between the housing shell element and the main surface, as well as the outer edges of the legs, increases the possibility of heat dissipation, since the heat generated by the PTC element can be dissipated to the outside via the main side surfaces as well as the outer circumferential surfaces of the legs.

[0022] The previously described design is preferably secured by an external clamping element, which typically leaves surface areas of the housing shell element(s) free so that heat dissipation can occur via these surface areas, while also bearing against the at least one housing shell element under preload. Accordingly, the external clamping element preferably exerts the preload force with which the housing shell element bears against the housing to seal the receptacle. The clamping element is preferably positively connected to the housing. This connection is usually achieved by bending locking tabs provided on the at least one clamping element.Preferably, first and second clamping elements are provided, each assigned to opposite main sides of the housing. These clamping elements typically bear against these main sides indirectly, with one of the housing shell elements interposed. Each clamping element has lateral locking lugs that are positively connected to the other clamping element to secure the pre-tensioned connection. Accordingly, the locking lugs of the first clamping element overlap the second clamping element and vice versa. The clamping element not only seals the housing shell element against the housing and / or the insulating layer, but preferably also creates a pre-tensioned connection of the insulating layer between the assigned housing shell element and the PTC element or the contact element provided between the PTC element and the insulating layer.The clamping element thus ensures good heat dissipation and electrical contact between the contact element and the surface of the PTC element. The pre-tensioned application of the insulating layer is preferably achieved such that the clamping element presses against the PTC element in a central area of ​​the main side surface.

[0023] The clamping element(s) are typically formed from a sheet metal strip produced by stamping and bending. To increase rigidity, the clamping element preferably has several stiffening ribs formed by stamping and bending. These stiffening ribs typically run transversely to the edges of the clamping element that have the locking ribs and are located at the level of the sealing bead to ensure maximum clamping force. Additionally or alternatively, a further stiffening rib is provided that covers the receptacle to keep the insulating layer pre-tensioned towards the PTC element. These additional stiffening ribs are preferably designed so that they only minimally contact the underlying housing shell element, allowing heat to be dissipated directly through it.The corresponding stiffening ribs can accordingly have recesses or be designed in such a way that they essentially bear against the housing shell element in a point-like or line-like manner.

[0024] To improve the sealing of the PTC heating element inserted in a receptacle of a heater housing, a preferred embodiment of the present invention proposes an inner housing made of an electrically insulating material, surrounded by a sealing collar and penetrated by the contact tongues. Plastic is preferably used as the electrically insulating material. The sealing collar can have external receptacles so that the contact tongues, penetrating the inner housing, are located between it and a receptacle for the inner housing formed by the sealing collar. However, separate bores in the inner housing, through which one of the contact tongues passes, are preferred. The corresponding bores are aligned with contact tongue receptacles formed during the injection molding of the housing, which open into the receptacle for the at least one PTC element within the housing.

[0025] The present invention further discloses a method for manufacturing a PTC element, particularly of the type mentioned above. In this method, the housing discussed above is first formed from the soft elastic plastic, preferably by injection molding. The PTC element and its associated contact elements are then inserted into the receptacle by elastically bending the housing legs that surround the receptacle. While, after manufacturing, the legs extend at right angles from the sealing collar that typically forms the contact tongue receptacles, elastic bending of the legs exposes an area behind the contact tongue receptacles such that no housing material is located in the extension direction of the contact tongue receptacles.The contact tongues can thus be inserted straight into the contact tongue receptacles, either together with the PTC element, inserted between the associated contact elements, which are already electrically and mechanically connected to the contact tongues, or first the contact tongues with the contact elements, with the PTC element subsequently inserted between the contact elements. After this assembly, the legs spring back to their original position, so that the PTC element and the contact elements are held in the receptacle and the contact tongues are exposed for electrical connection on the side of the sealing collar opposite the receptacle.

[0026] Insulating layers are then typically applied to the housing on both sides of the recesses. Preferably, the outer surfaces of the two insulating layers are then also attached to the housing shell elements. Connecting two clamping elements against each other, which are applied to the outside of the housing shell elements, creates a seal around the recess, as the clamping elements compress the soft, elastic plastic material of the housing.

[0027] Further details and advantages of the present invention will become apparent from the following description of two exemplary embodiments in conjunction with the drawing. The drawing shows: Fig. 1 a perspective side view of the housing of the embodiment; Fig. 2 a perspective side view of the housing shell element of the embodiment; Fig. 3 a perspective side view of the clamping element of the embodiment; Fig. 4 a perspective front view of the embodiment; Fig. 5 a sectional view along line VV according to the representation in Fig. 4; Fig. 6 a perspective top view of components of a second embodiment during manufacturing; Fig. 7 a view after Fig. 6 after a further manufacturing step; and Fig. 8 an electric heating device that incorporates the PTC heating element.

[0028] The Fig. Figure 1 shows a housing 10, which is uniformly formed from a soft elastic plastic and forms a sealing collar 11, which is tapered towards its free end and defines a flange surface 12 on the opposite side, from which first legs 13 and second legs 14 of the housing 10 extend at right angles, defining a frame and a receptacle 15 surrounded thereby.

[0029] Fig. Figure 1 shows 15 contact tongue receptacles 16 within the recess, which, as through holes, penetrate the sealing collar 11 from the inside. A ventilation hole 17 is recessed between the contact tongue receptacles 16, which also penetrates the sealing collar 11.

[0030] On opposite main sides 18 of the frame-shaped housing 10 surrounding the intake 15, a sealing bead 19 is formed by the soft elastic material of the housing 10 and is formed in one piece with it.

[0031] How in particular Fig. As can be seen in section 5, the sealing collar 11 is provided with a labyrinth seal 20, which is described below. Fig. 8 will be discussed further.

[0032] The sealing bead 19 is clearly completely closed and surrounds the receptacle 15 at a certain distance. The legs surrounding the receptacle 15 extend, on the one hand, parallel to the longitudinal direction of the sealing collar 11. These are the legs with reference numeral 13. The legs marked with reference numeral 14 have a longitudinal direction perpendicular to the first legs 13.

[0033] The in Fig. The design 1 recognizable on the main surface 18 of the housing 10 is formed correspondingly on the underside of the legs 13 / 14, which is not shown.

[0034] The housing 10 is made of a soft elastic material which is commonly used in housing seals, for example EPDM or silicone.

[0035] The Fig. Figure 2 shows a housing shell element 30, which is formed from a sheet material, in this case AlMg3, by stamping and bending. The housing shell element 30 has a base surface 31 and four edges bent at 90° relative to the base surface 31, of which the downwardly bent edges are designated by reference numeral 32 and the upwardly bent edge to the opposite side is designated by reference numeral 33.

[0036] The Fig. Figure 3 shows a clamping element 40, which forms a contact segment labelled 41 and a locking segment 42 extending perpendicular to it. The contact segment 41 has approximately the same dimensions as the base 31. The clamping element 40 is preferably made of stainless steel. As the curved dashed line in Fig. As indicated in Figure 3, the clamping segment 41 can be pre-tensioned wholly or partially inwards, so that the clamping element 40 against the housing shell element 30 results in an increased pre-tensioning force. The clamping element 40 has several stiffening ribs, of which the outer stiffening ribs are designated by reference numeral 43, a middle stiffening rib by reference numeral 44, and inner stiffening ribs by reference numeral 45.

[0037] The stiffening ribs 43, 44, 45 extend transversely to the locking segment 42 and, in the assembled state, parallel to the second legs 14, i.e., the longitudinal extent of the sealing collar 11. The stiffening ribs 43, 44, 45 are each formed by punching and bending the sheet metal material forming the clamping element. The middle stiffening rib 56 is provided with recesses 46 punched out of the sheet metal material. The inner stiffening ribs 45 are relatively narrow compared to the other stiffening ribs 43, 44, so that they have a relatively small contact area for direct contact with the base surface 31.

[0038] The locking segment 42 has several locking lugs 47, the function of which will be explained below. The exemplary embodiment has two identically designed clamping elements 40.

[0039] The exemplary embodiment further includes a fundamentally in Fig. 6 PTC element 50 shown, which in any case in the embodiment according to Fig. 6 with its main side surface is already in contact with a contact element designated by reference numeral 51. This contact element 51 is manufactured by stamping and bending and forms a contact tongue designated by reference numeral 52 in one piece. The in Fig. The heat-generating cell 5, which can be identified, further comprises insulating layers 57, which in the illustrated embodiment are applied to both sides against the contact elements 51 and cover the receptacle 15, so that edge areas of the insulating layers 57 are applied to and abut the edges 21 of the housing 1 surrounding the receptacle 15. Fig. Figure 5 illustrates that the sealing bead 21 completely surrounds the insulating layer 57.

[0040] The Fig. 6 and Fig. Figure 7 shows an alternative embodiment in which the insulating layer 57 is arranged within the receptacle 16. Thus, the insulating layer 57 does not protrude beyond the receptacle. A [missing text] in the Fig. 6 and Fig. Unit 7, designated with reference numeral 59, comprises a terminal holder 54 equipped with pins 53 for positioning the contact element 51. The contact tongues 52 of the contact element 51 have bores into which the pins 53 can be inserted for positioning. Each pin 53 projects from the base of a U-shaped recess 55, which receives the contact tongue 52 with minimal play. This also results in a relative positioning of the contact element 53 relative to the terminal holder 54. Fig. Figure 6 further illustrates an edge insulation 56, which consists of a silicone bead applied around the PTC element 50 and the contact element 51 to electrically seal both components at their edges. This measure increases the creepage distance from the contact element 51 to the opposite main side surface of the PTC element 50, which is also to be fitted with a contact element.

[0041] Also in Fig. Reference numeral 57 6 designates the insulating layer, which in this case is in the form of a ceramic plate that is placed against the outer surface of the contact element 51 and is bonded to the contact element 51 and the PTC element 50 by the edge insulation 56.

[0042] In a corresponding manner, the other contact element and the one in Fig. 7 The already applied insulating layer 57 is glued and the edge insulation 56 improves the air and creepage distance between the two contact elements 51. For the sake of a clearer illustration of the positions of the in Fig. In the layer structure shown in Figure 7, the depiction of the edge insulation 56 has been omitted. Thus, the insulating layers 57 are visible on the outside, onto which the contact element 51 is glued on the inside and at a distance from the edge of the insulating layer 57, which in turn is flush with the PTC element 50.

[0043] The connection holder 54 can, for example, be connected to the heat-generating cell of the exemplary embodiment by hot-stitching the pins 53. Alternatively, the cell can be removed from the connection holder 54 and mounted in the housing 10 without the holder. Which of the two alternatives is chosen depends on the available space provided by the PTC heater. If the connection holder 54 is installed in the housing 10, it has a ventilation passage 58 which, when installed, communicates with the ventilation bore 17.

[0044] For assembly, the injection-molded housing, together with the unit designated by reference numeral 59, consisting of the PTC element 50, the contact elements 51, the contact tongues 52, and the two insulating layers 57, is first inserted into the receptacle 15. For this purpose, the first legs 13 are elastically bent. Accordingly, the contact tongues 52, cut from sheet metal, can be inserted into the corresponding contact tongue receptacles 16, aligned with them, until the unit 59 abuts the stop formed by the inner first leg 13. The first legs 13 can be bent and positioned using an assembly aid. After releasing this positioning, the wider legs 14 spring back elastically, so that the outer second leg 14 lies behind the unit 59.

[0045] The insulating layer 57 then lies on both sides in the recess 15 and covers the PTC element 50.

[0046] The two housing shell elements 30 are now placed against the outer surface of the insulating layer 57, such that the edge 33 rests against the flange surface 12 and extends parallel to it. The other edges 32 enclose the outer circumferential surface of the housing, formed by the legs 13, 14 and projecting from the flange surface 12, with minimal clearance. Typically, the edges 32 rest against these surfaces, at least when the housing shell elements 30 are pre-tensioned against each other. This pre-tensioning deforms the sealing bead 19, causing it to seal against the corresponding housing shell element 30.

[0047] In this embodiment, the necessary clamping force is generated by the two clamping elements 40, whose contact segment 41 is pressed against the base surface 31 of the housing shell element 30. The locking lugs 47 are bent over while maintaining an external clamping force, typically applied by an assembly aid, so that they engage the other clamping element 40 at the level of the outer and middle stiffening ribs 43, 44. The two clamping elements 40 are then crimped together and positively locked against each other under preload. After the assembly aid is released, the clamping force exerted by the clamping elements 40 maintains the previously applied preload. The receptacle 15 is permanently sealed. This is evident for the first embodiment from the Fig. 4 and Fig. 5, but is also achieved when the insulating layer 57 is located within the inlet 15.

[0048] At the end of the assembly, a [unclear text] is usually [unclear text]. Fig. The inner housing 70, marked with reference numeral 70, is pushed over the free ends of the contact tongues 52 until it is received in a recess 71 formed for this purpose within the sealing collar 11. The inner housing 70 is made of an engineering plastic, for example PE, PA, or PC. The inner housing 70 is in any case formed from a rigid component, so that the sealing collar 11 is reinforced and stiffened on the inside in the area of ​​the labyrinth seal 20.

[0049] The inclusion of the reference to the Fig. The embodiment discussed in points 1 to 7 in a PTC heater is in Fig. Figure 8 illustrates this.

[0050] The heater has a plastic housing designated by reference numeral 1. The housing 1 forms inlet and outlet ports 2, each defining inlet and outlet openings 3 respectively, which lead to a circulation chamber 4. This chamber is fluid-tightly separated from a connection chamber designated by reference numeral 6 by a cover flap 5 and forms heating element receptacles 7. These receptacles are designed as female plug elements of a fluid-tight plug connection, which is effected by inserting the sealing collar 11 into the heating element receptacle 7. In this, Fig. In the position shown in Figure 9, the contact tongues 52 protrude into the connection chamber 6 with their free terminal ends and can be electrically connected there, as is generally described, for example, in EP 3 344 244 A1.

[0051] In the embodiment described there, the PTC heating elements are secured against the bottom of the circulation chamber 4 in the heating element receptacle 7 by means of an elastic connection. Such an elastic connection is also possible with the present invention if, for example, the housing shell elements 30 are provided with recesses at their end associated with the second outer leg 14, and projections formed during the initial shaping of the housing 10 extend from the second leg 14, which can be pressed against the bottom of the circulation chamber, since these projections extend beyond the housing shell elements 30 on the side opposite the sealing collar 11. Reference symbol list 1 case 2 inlet / outlet ports 3 Inlet / outlet openings 4 Circulation chamber 5 Cover plate 6 connection chamber 7 Heating element holder 10 cases 11 Sealing collar 12 flange area 13 first thigh 14 second thigh 15 recording 16 Contact tongue insertion 17 ventilation holes 18 Main page 19 Sealing bead 20 Labyrinth seal 30 Housing shell element 31 Base area 32 Rand 33 Rand 40 clamping elements 41 Investment segment 42 Locking segment 43 outer stiffening rib 44 middle stiffening rib 45 inner stiffening rib 46 Exclusion 47 Locking bar 50 PTC elements 51 Contact element 52 Contact tongue 53 cones 54 connector holders 55 U-shaped recess 56 edge insulation 57 Insulation layer 58 Mounting passage 59 units 70 inner housings 71 Exclusion

Claims

[1] PTC heating element with a frame-shaped housing (10) forming a receptacle (15) for at least one PTC element (50), which forms a sealing collar (11) that is provided between contact tongues (52) which are electrically connected to contact elements (51) via which the PTC element (50) is electrically contacted, and the PTC element (50), wherein the frame (10) is made of a soft elastic plastic material and the PTC element (50) is covered on the outside of the housing (10) with an insulating layer (57), characterized by , that the receptacle (15) is a receptacle (15) adapted for the insertion of the PTC element (50) and that the receptacle (15) is adapted such that the PTC element (50) is exposed in the receptacle (15) with its opposite main side surfaces. [2] PTC heating element according to claim 1, characterized by, that the insulating layer (57) is applied to the housing (10) against the edges (21) surrounding the receptacle (15) and that the housing (10) forms a sealing bead (19) surrounding the receptacle (15) and completely enclosing the insulating layer (57). [3] PTC heating element according to one of the preceding claims, characterized by at least one housing shell element (30) that is exposed on the outside of the PTC heating element and at least partially surrounds the housing (10). [4] PTC heating element according to claim 3, characterized by , that the housing shell element (30) is directly against a main side (18) of the housing (10). [5] PTC heating element according to any of the preceding claims, characterized by , that the housing (10) forms a sealing bead (19) surrounding the receptacle (15), against which at least one housing shell element (30) seals. [6] PTC heating element according to one of claims 3 to 5, characterized by, that two preferably identically designed housing shell elements (30) are applied to opposite main sides (18) against the housing (10). [7] PTC heating element according to one of the previous claims characterized by an outer clamping element (40) which is under preload against at least one housing shell element (30). [8] PTC heating element according to claim 7, characterized by , the clamping element (40) is under preload against the insulating layer (57). [9] PTC heating element according to claim 7 or 8, characterized by , that the clamping element (19) is made of sheet metal and has several stiffening ribs (43, 44, 45) formed by punching and bending. [10] PTC heating element according to any one of claims 6 to 9, characterized bya first and a second clamping element (40), each bearing against the at least one housing shell element (30) on opposite main sides (18) and each having lateral locking webs (47) which positively engage the other of the clamping elements (30) to secure a pre-tensioned position of the at least one housing shell element (30) against the housing (10). [11] PTC heating element according to one of the preceding claims, characterized by an inner housing (70) surrounded by the sealing collar (11) made of an electrically insulating material, which is penetrated by the contact tongues (52). [12] PTC heating element according to any of the preceding claims insofar as dependent on claim 4, characterized by , that at least one housing shell element (30) is exposed on an outer surface of the PTC heating element which is swept by a fluid to be heated. [13] Method for manufacturing a PTC heating element in which a frame-shaped housing (10) forming a receptacle (15) for at least one PTC element (50) and a sealing collar (11) is first formed from a soft elastic plastic, then the PTC element (50) and associated contact elements (51) are inserted into the receptacle (15) by elastically bending the legs (13, 14) of the housing surrounding the receptacle (15) and inserting contact tongues (52) associated with the contact elements (51) into openings (16) provided in the housing (10). [14] Method according to claim 13, wherein the PTC element (50) and insulating layers (57) covering both sides are inserted into the receptacle (15) together with the PTC element (50) and the contact elements (51) as a pre-assembled unit (59). [15] Method according to claim 132, wherein after the insertion of the PTC element (50) and the contact elements (51) into the receptacle (15) insulating layers (57) are applied on both sides against the contact elements (51). [16] Method according to any one of claims 13 to 15, characterized by , that housing shell elements (30) are placed against the insulating layers (57) on both sides and that by connecting two clamping elements (40) placed on the outside against the housing shell elements (30) a sealing of the receptacle (15) is achieved by compressing the soft elastic plastic.

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