PTC heating element

Abstract

The present invention relates to a PTC heating device (2) with at least one PTC element (8), electrically contacted conductor elements (10) thereto which are assigned different polarities, and a housing (4) which forms at least one receptacle (6) in which the PTC element (8) is arranged and which has a connection side (16) on which contact tongues (18) assigned to the conductor elements (12) are exposed, with a wedge (32) which has a wider and a narrower end surface (40; 42) which are provided one behind the other in an insertion direction (38) of the wedge (32), with a sliding plate (22) which is arranged between the wedge (32) and the PTC element (8) and has an inner surface (48) opposite the wedge (32) which is directed towards the PTC element (8), and with an electrical insulating layer (20) arranged between the inner surface (48) and the PTC element (8).To increase electrical safety, it is proposed that the inner surface (48) be contoured by a plateau (50) projecting towards the PTC element (8).

Description

[0001] The present invention relates to a PTC heating element that can be used in an electric heating device, such as that known from DE 10 2019 216 481 A1. The previously known electric heating device has a housing with a partition wall that separates a heating chamber for a liquid medium to be heated, which is provided on the housing via inlet and outlet ports, from a connection chamber. At least one heating fin projects from the partition wall, forming a receiving pocket open to the connection chamber. The PTC heating element is received in this receiving pocket.

[0002] The aforementioned electric heating device can also be an embodiment of the present invention, although this alone proposes an improvement on the PTC heating device.

[0003] The PTC heating device according to the invention has at least one PTC element, which is a ceramic, usually cuboid-shaped body contacted by conductor elements. These conductor elements can be contact plates that bear directly against a surface of the PTC element. The contact surface of the PTC element has a metallization applied to the surface of the ceramic component by sputtering or a similar process. Current is introduced through this metallization and propagates over the surface of the ceramic component.

[0004] It is understood that the conductor elements are assigned different polarities. The PTC heating device also has a housing, which is usually designed as a frame-like enclosure and forms at least one recess in which the at least one PTC element is arranged. The conductor elements may also be provided within the recess.

[0005] To maximize air and creepage distances, the conductor elements are typically arranged on opposite sides of the PTC element. The housing has a connection side where contact tongues associated with the conductor elements are exposed. These contact tongues usually extend beyond the housing on the connection side and serve to connect the PTC heating element to the connection chamber of the electrical heating device.

[0006] The PTC heating device according to the invention further comprises a wedge having a wider and a narrower end surface, which are arranged one behind the other in a direction of the wedge referred to as the insertion direction. Finally, the PTC heating device has at least one sliding plate, which is arranged between the wedge and the PTC element and has an inner surface opposite the wedge, facing the PTC element.

[0007] During assembly, such a PTC heating element is inserted into the aforementioned receiving pocket of the electric heating device. The wedge is then moved in the insertion direction relative to the PTC element and along the surface of the sliding plate. The sliding plate is typically fixed in place, as described, for example, in EP 2 637 474 A1. The sliding plate serves to protect the functional components of the PTC heating element, which are responsible for heat generation and conduction, and, where applicable, for the electrical insulation of the current-conducting parts of the PTC heating element. The sliding plate prevents direct mechanical interaction between the wedge and any of these components of the PTC heating element.

[0008] For electrical insulation of the conductive parts of the PTC heating element from its outer surface, an insulating layer is arranged between the inner surface of the sliding plate and the PTC element. In the present invention, this insulating layer can be in direct contact with the outer surface of the PTC element and / or with the outer surface of the conductor element. The insulating layer is preferably positioned relative to the housing such that it extends circumferentially beyond the PTC element. The insulating layer can be bonded to the housing or injection molded into it. The insulating layer should, as far as possible, reliably electrically insulate the housing and the electrical functional elements contained therein, such as the conductor elements and the at least one PTC element, from the outer surface of the PTC heating element, and optionally also seal the housing.

[0009] Particularly when operating the electric heating element or the electrical heating device housing it at high voltage in an electric vehicle, stringent electrical safety requirements apply. In addition to the aforementioned sealing of the housing from the environment or the typically metallic heater casing that forms the housing pocket, corresponding requirements must be met for the insulating layer. This layer can be multi-layered and, for example, comprise a ceramic plate and a plastic film. The former has high dielectric strength, while the latter compensates for certain roughnesses of the adjacent surface and / or may be bonded to the ceramic plate to hold it in position should the ceramic plate break due to excessive stress.

[0010] Such a breakage is a risk, for example, when inserting the wedge element. The wedge element is positioned opposite a main side face of the PTC element. The PTC element typically has two main side faces extending parallel to each other, each of which is usually at least five times larger than any other surface, which is a connecting side face of the cuboid PTC element. During the assembly of the PTC heating element, the wedge element is moved within the receiving pocket to ensure good thermal and / or electrical contact between the electrically conductive and / or heat-dissipating layers of the PTC heating element. It has been shown that the efficiency of the PTC element increases with the pressure applied to it within the receiving pocket. Dimensional deviations, or...However, roughness can cause an insulating layer, especially one made of a ceramic material, to break under excessive pressure.

[0011] The present invention aims to provide an electric heating device that addresses this risk in an improved manner.

[0012] The present invention proposes that the inner surface of the sliding plate be contoured by a plateau projecting towards the PTC element. This plateau is typically adapted to the area where the wedge's contact force is to act most heavily on the PTC element, relative to the planar extent of the sliding plate. This area may also be only a portion of the main side surface of the PTC element. The projecting plateau ensures that the contact force applied by the wedge is not distributed evenly across the entire planar extent of the sliding plate parallel to the corresponding main side surface, but rather only locally, preferably at the level of the PTC element, and particularly preferably on an area approximately corresponding to one of the main side surfaces.In a top view of the main side surface, the outer contour of the plateau therefore preferably follows essentially the contour of the PTC element.

[0013] The projecting plateau can be formed by the wedge and / or the insulating layer and / or a plateau element conventionally connected to a wedge or insulating layer. The plateau element is preferably formed by a highly thermally conductive plate.

[0014] It is understood that the surface of the plateau is flat and designed to fit snugly against the sliding plate in a parallel direction to the main side surface of the underlying PTC element. The recessed areas of the wedge's inner surface, relative to the plateau, can meet less stringent dimensional requirements. They are typically recessed by at least 0.5 to 2 mm, preferably by 0.75 to 1 mm, relative to the plateau's contact surface. The plateau is usually completely surrounded by these additional areas of the inner surface, since the receptacle, and thus the PTC element, is also typically completely enclosed by the housing material, and the sliding plate extends to the lower end of the housing in the insertion direction, sometimes even forming a U-shape around it.

[0015] Preferably, the sliding plate is U-shaped with two legs that receive the PTC element between them and a connecting web. The inner surfaces of each leg are contoured by a plateau projecting towards the PTC element. This ensures that the sliding plate makes specific contact with the PTC element from both sides and against both main side surfaces.

[0016] According to a preferred embodiment of the present invention, positioning means are provided for positioning the wedge and / or the sliding plate relative to the housing and thus to the PTC element. These include, for example, positioning jaws that laterally grip the sliding plate and / or the wedge on both sides. These jaws can be provided on the sliding plate, which is connected to the housing by means of positive locking and is precisely positioned relative to it. However, the positioning jaws are preferably formed on the housing. Accordingly, the positioning jaws project outwards beyond the insulating layer on at least one side and provide lateral support and guidance for the sliding plate and / or the wedge. These positioning jaws can also clamp the wedge between them, so that it is temporarily held between the positioning jaws during assembly and can be inserted into the receiving pocket together with the other elements of the PTC heating device.

[0017] It is understood that a wedge can be provided on both sides of the PTC element. The PTC element should be cooled as uniformly as possible on both main side surfaces, which promotes a symmetrical arrangement of the PTC heating element between the opposing inner surfaces of the receiving pocket. This allows identical layers with identical structure and identical thickness (extending in the direction of heat conduction / extending perpendicular to the planar extent of the main side surface) to form on both sides of the main side surfaces.

[0018] The positioning means can include positive locking elements on the housing and / or the sliding plate, which ensure that the sliding plate and the housing are positively locked relative to each other, particularly in the insertion direction. The positioning means serve, in particular, to keep the plateau positioned relative to the main side surface of the PTC element or the receptacle and to prevent this positioning from being lost during assembly, especially when the wedge is moved. For example, the sliding plate can have projections on its inner surface that engage in recesses in the housing to hold and secure the sliding plate in a predetermined position relative to the PTC element in the insertion direction and transversely thereto. The aforementioned web of the sliding plate can also interact with the housing to positively lock the sliding plate in position.Such positioning is achieved, for example, by the bridge interacting with a front face of the housing in the insertion direction, for example by resting against it or engaging with it and / or by being connected to it in some other way, for example by being latched or glued.

[0019] According to a further preferred embodiment of the present invention, the wedge and the sliding plate are realized in a single component. In such an embodiment, the entire PTC heating element can be inserted into the receiving pocket and pressed into it until the necessary clamping of the individual layers of the PTC heating element in the receiving pocket is achieved, without any relative movement occurring between the wedge and the PTC element. The sliding plate and the wedge are preferably positively locked to the housing and thus to the PTC element in the manner described above, so that no relative movement can occur between them during clamping. Necessarily, the wedge does not provide a sliding surface on which it could slide on the outside of the sliding plate.

[0020] However, this functionality has an equally possible embodiment in which the wedge is implemented within a wedge element. The wedge element and the sliding plate are separate components that are joined and positioned relative to each other in a predetermined manner only after the PTC heating element has been mounted in the receiving pocket.

[0021] The positioning means can also include a contact surface, particularly on the housing, which interacts with the insulating layer to hold it in the receptacle. The receptacle can be stepped and slightly widened near the housing surface, so that an insulating layer projecting beyond the main side surface of the PTC element is at least partially supported at its edges by recessed grooves within the housing. The housing is designed to accommodate the layering of the two insulating layers with the PTC element positioned between them and the conductor elements typically located against the main side surfaces, such that the clamping force acts from the outside against the PTC element, and neither the conductor element nor the insulating layer transmits any of the clamping force to the housing, thus preventing them from bearing against the housing.Even if the conductor element and / or the insulating layer accordingly protrude beyond the main side surface of the PTC element, the part of the receptacle accommodating the conductor element and the insulating layer is preferably dimensioned in such a way that no support of the conductor element and / or the insulating layer can take place on opposite sides of the PTC element and against the housing.

[0022] Further details and advantages of the present invention will become apparent from the following descriptions in conjunction with the drawing. The drawing shows: Fig. 1 a perspective side view of a first embodiment; Fig. 2 a sectional view along line II-II according to the illustration in Fig. 1; Fig. 3 a view according to Fig. 1 for a second embodiment of the present invention and Fig. 4 a sectional view according to Fig. 2 for the second embodiment.

[0023] The exemplary embodiments each comprise a PTC heating device 2 with a frame-shaped housing 4, which forms a receptacle 6 in which a PTC element 8 is received. The PTC element 8 is electrically contacted and connected on both sides to adjacent conductor elements 10 in the form of contact plates 12 in order to supply the PTC element with opposite polarities. It is understood that the conductor elements 10 are supported within the housing 4 in an insulated manner.

[0024] Reference numeral 16 indicates a connection side of the housing 4 where contact tongues 18 are exposed, which are provided for plugging the PTC heating device into a power current source and are each electrically connected to one of the conductor elements 10.

[0025] In the thickness direction of the layered structure according to Fig. 2 the conductor elements 10 are each covered on the outside with an insulating layer 20, which are at least partially included in the receptacle 6 and are in this case made of aluminium oxide or aluminium nitride.

[0026] On the outside of these electrical insulating layers 20 there is a sliding plate 22, which in this case is U-shaped with two legs 24 that receive the PTC element 8 between them and a web 26 connecting the legs 24.

[0027] As the section view according to Fig. As illustrated in Figure 2, the PTC element 8 is cuboid in shape and has two opposing main side surfaces 28, through which heat dissipation occurs and which are provided with a metallization via which the PTC element is electrically contacted with the conductor elements 10. These main side surfaces 28 are connected to each other by circumferential edge surfaces 30.

[0028] In contrast to the one in Fig. A wedge 32 in the form of a separate wedge element 34 is provided on the upper main side surface 28 and against the outer surface of the sliding plate 22. This wedge element 34 is slidably mounted on an outer surface 36 of the sliding plate 22, specifically the upper leg 24, in an insertion direction designated by reference numeral 38. The insertion direction 38 is characterized in that a wider end surface 40 of the wedge element 34 and a narrower end surface 42, extending parallel to the wider end surface 40, are arranged one behind the other in this insertion direction 38. While the wedge element 34 is slidably displaceable relative to the sliding plate 22 in this insertion direction 38, positioning means 44 are provided which prevent movement of the wedge element 34 in a direction transverse to the insertion direction 38. In the exemplary embodiments, these positioning means 44 are formed by positioning cheeks 46 which are integrally formed on the housing 4.In the thickness direction, these positioning cheeks 46 end below the outer surface of the wedge element 34 (cf. . Fig. 2) The positioning cheeks 46, however, rest against opposite cheek surfaces of the wedge element 34 and can grip the wedge element 34 by clamping it against the sliding plate 22, but allowing it to move in the insertion direction 38. In this case, the positioning cheeks 46 also grip the upper leg 24 of the sliding plate 22 laterally, so that it is positioned in a predetermined orientation relative to the receptacle 6.

[0029] How Fig. As can be seen in Figure 2, each leg 24 has a plateau 50 on its inner surface 48 facing the PTC element 8, which projects towards the PTC element 8 compared to the remaining surface areas of the inner surface 48. Fig. As mediated by the wedge element 34, the length of the plateau 50 extends over the longitudinal extent (extension in the insertion direction 38) of the receptacle 6. The same applies to the transverse lateral extent. Thus, a compressive force acting externally by the wedge element 34 is transmitted via the plateau 50 exclusively to the PTC element 8 and the adjacent layers, namely the conductor elements 10 and the electrical insulating layers 20. Surface areas of the contact plate 12 and / or the insulating layer 20 located beyond the main side surface 28 of the PTC element 8 are not subjected to pressure.

[0030] This contouring of the inner surface 48 accordingly provides mechanical relief, in particular to the electrical insulation layer 20, so that it is less stressed when clamping the PTC heating device by moving the wedge element 34 in a receiving pocket.

[0031] The following description of the second embodiment according to Fig. Section 3 essentially refers to the previous description. The main difference is that in the second embodiment, a wedge 32 is provided on opposite sides of the PTC element 8. This wedge 32 is integrally formed with the sliding plate 22.

[0032] The positioning cheeks 46 – as in the first embodiment – ​​essentially form contact surfaces 52 extending parallel to the main side surface 28 of the PTC element 8. These contact surfaces 52 cover the insulating layer 20 on the outside and accordingly fix the insulating layer 20 relative to the housing 4. On the opposite side, the insulating layer 20 may be bonded to the housing 4 or connected to it by overmolding.

[0033] In this embodiment, positioning means 44 are provided by forming detent projections 54 on the sliding plate 22, which engage in detent receptacles 56 formed on the housing 4. This positions the housing 4, and thus the PTC element 8, relative to the legs 24 and thus the wedges 32 of the exemplary embodiment. After the PTC heating device 2 has been mounted, the plates 50 are positioned relative to the PTC element 8 in a predetermined manner.

[0034] In this embodiment, clamping is achieved by inserting the entire PTC heating device 2 into a receiving pocket of the electric heating device, which is conically shaped, so that as the insertion movement progresses, the individual layers of the PTC heating device are clamped without – as in the first embodiment – ​​any movement of the part relative to the PTC element having to take place. Reference symbol list 2 PTC heating elements 4 cases 6 recording 8 PTC elements 10 conductor elements 12 contact plates 16 Connection side 18 contact tongues 20 electrical insulation layer 22 Sliding plate 24 thighs 26 Bridge 28 Main page area 30 Edge area 32 wedge 34 wedge element 36 outdoor area 38 Insertion direction 40 wider end surface 42 narrower end face 44 Positioning devices 46 positioning cheeks 48 interior surface 50 Plateau 52 investment areas 54 resting projections 56 rest shots QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2019 216 481 A1

[0001] EP 2 637 474 A1

[0007]

Claims

[1] PTC heating device (2) with at least one PTC element (8), electrically contacted conductor elements (10) assigned to it of different polarity, and a housing (4) which forms at least one receptacle (6) in which the PTC element (8) is arranged, and which has a connection side (16) on which contact tongues (18) assigned to the conductor elements (10) are exposed, with a wedge (32) having a wider and a narrower end face (40; 42) arranged one behind the other in an insertion direction (38) of the wedge (32), with a sliding plate (22) arranged between the wedge (32) and the PTC element (8) and having an inner surface (48) facing the PTC element (8) opposite the wedge (32), and with an electrical insulating layer (20) arranged between the inner surface (48) and the PTC element (8) characterized by , that the inner surface (48) is contoured by a plateau (50) projecting towards the PTC element (8). [2] PTC heating device (2) according to claim 1, characterized by , that the base area of ​​the plateau (50) essentially corresponds to a main side surface (28) of the PTC element (8) and that the plateau (50) is arranged opposite the main side surface (28). [3] PTC heating device (2) according to claim 1 or 2, characterized by , that the sliding plate (22) is U-shaped with two legs (24) receiving the PTC element (8) between them and a web (26) connecting the legs (24), and that the inner surface (48) of the two legs (24) is contoured by a plateau (50) projecting towards the PTC element (8). [4] PTC heating device (2) according to any one of the preceding claims, characterized by Positioning means (44; 46; 54; 56) for positioning the wedge (32) and / or the sliding plate (22) relative to the housing (4). [5] PTC heating device (2) according to claim 4, characterized by, that the positioning means have positioning cheeks (46) which laterally grip the sliding plate (22) and / or the wedge (32) on both sides and which are formed on the housing (4). [6] PTC heating device (2) according to claim 5, characterized by , that the insulating layer (20) is received in the receptacle (6) and that the positioning cheeks (48) form contact surfaces (52) which interact with the insulating layer (20) and hold the insulating layer (20) in the receptacle (6). [7] PTC heating device (2) according to claim 5 or 6, characterized by , that the positioning means (44; 46; 54; 56) comprise positive locking means (54; 56) provided on the housing (4) and the sliding plate (22) by which the sliding plate (22) and the housing (4) are positively positioned relative to each other in the insertion direction (38). [8] PTC heating device (2) according to any one of the preceding claims, characterized by , that the wedge (32) and the sliding plate (22) are realized in a single component.

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