Electric Heating Device and Method for Manufacturing the Same

Abstract

An electric heating device includes a housing which forms a receiving pocket in which at least one PTC heating assembly with at least one PTC element received in a positioning frame and strip conductors electrically conductively connected to the PTC element for energizing the PTC element with different polarity is received. In order to compensate for manufacturing tolerances without significantly impairing the heat dissipation from the PTC element, at least one profile part is connected opposite main side surfaces of the PTC element in a heat-conducting manner. Outer main side surfaces of the profile parts opposite the PTC element are connected to an inner surface of the receiving pocket in a heat-conducting manner in each case. The profile parts are connected to the positioning frame.

Claims

1. An electric heating device comprising: a housing forming a receiving pocket; a positioning frame that is disposed in the receiving pocket; a PTC element and strip conductors that are received in the positioning frame, the strip conductors being electrically conductively connected to the PTC element for energizing the PTC element with different polarity, wherein at least one profile part is connected in a heat-conducting manner to the PTC element on each of two opposite main side surfaces of the PTC element, wherein outer main side surfaces of the profile parts opposite the PTC element are connected in a heat-conducting manner to an inner surface of the receiving pocket in each case, and wherein the profile parts are connected to the positioning frame.

2. The electric heating device according to claim 1, wherein the profile parts are clipped to the positioning frame.

3. The electric heating device according to claim 1, wherein the positioning frame has an upper cross beam surmounted on one side thereof by contact tongues, and on an opposite side thereof by a lower cross beam, and wherein form-fit segments each extend from the cross beams and engage over associated profile parts.

4. The electric heating device according to claim 3, wherein at least one of the cross beams has a form-fit segment formed in the manner of an engaging pawl.

5. The electric heating device according to claim 1, wherein the profile parts are each formed by extruded profiles made of metal.

6. The electric heating device according to claim 5, wherein the metal is aluminum.

7. The electric heating device according to claim 1, wherein an electrically insulating layer is provided between each of the profile parts and the strip conductors.

8. The electric heating device according to claim 1, wherein the profile parts are connected to the receiving pocket via a tongue and groove joint extending in an insertion direction (E) of the receiving pocket.

9. The electric heating device according to claim 8, wherein the tongue and groove joint has at least one groove limiting projection limiting the groove and at least one tongue projection at least partially forming the tongue, which tongue is received within the groove for forming the tongue and groove joint, and wherein at least one of the groove limiting projection and the tongue projection can be pivoted about an axis extending in the insertion direction (E).

10. The electric heating device according to claim 1, wherein the housing comprises a partition wall which separates a connection chamber from a heating chamber for dispensing heat and from which at least one heating rib protrudes towards the heating chamber and forms the receiving pocket.

11. A method for producing a PTC heating assembly for an electric heating device, the electric heating device including a housing which forms a receiving pocket in which the PTC heating assembly is received, the PTC heating assembly including at least one PTC element which is received in a positioning frame and strip conductors which are electrically conductively connected to the PTC element for energizing the PTC element with different polarity and which are each covered on an outside surface thereof with at least one insulating layer, the method comprising: applying insulating layers on the outside against the strip conductors such that the insulating layers are held via the positioning frame; and applying profile parts against the insulating layers with the profile parts being held on an outside of the respective insulating layer facing away from the PTC element by a connection of the profile parts to the positioning frame between the insulating layer and the profile part so as to form a structural unit comprising the the position frame, the PTC element, the strip conductors, the insulating layers, and the profile parts.

12. The method according to claim 11, further comprising inserting the formed structural unit into the receiving pocket.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Further details of the present invention will be apparent from the following description of an embodiment in conjunction with the drawing. Therein:

[0034] FIG. 1 shows a perspective exploded view of an embodiment of a PTC heating assembly;

[0035] FIG. 2 shows a perspective exploded view of the PTC heating assembly according to FIG. 1 with a housing of an electric heating device shown in sections;

[0036] FIG. 3 shows a cross-sectional view of a part of the electric heating device;

[0037] FIG. 4 shows a sectional view along line III-III as shown in FIG. 3; and

[0038] FIG. 5 shows a sectional view according to FIG. 4 for one variant.

DETAILED DESCRIPTION

[0039] FIG. 1 shows a PTC heating assembly 2 with a PTC element 4, on the main side surfaces of which there are strip conductors 6 in the form of sheet metal strips, which are covered on the outer surface opposite the PTC element 4 by insulating layers 8, which in this case consist of ceramic plates. Reference sign 10 characterizes an injection-molded positioning frame made of plastic, which forms a receptacle 18 for the PTC element 4 between two cross beams, of which the upper cross beam is characterized by reference sign 12 and the lower cross beam by reference sign 14, and two longitudinal beams 16 extending at right angles to the cross beams 12, 14. The contact sheets forming the strip conductors 6 have contact tongues 20 integrally formed thereon by punching, which are provided at opposite ends of the positioning frame 10 in the longitudinal direction of the upper cross beam 12 and are received in lead-through openings of the upper cross beam 12.

[0040] Form-fit segments 22 with engaging pawls 24 project opposite each other from the cross beams 12 at their outer ends. These special form-fit segments 22 project beyond the upper cross beam 12 in the width direction.

[0041] The form-fit segments 22 or the engaging pawls 24 are located at the outer edge of the positioning frame 10 in extension of the longitudinal beams 16 and thus outside the main side surface of the PTC element 4. The main side surface of the PTC element 4 is formed by the respective largest surface of the cuboid PTC element 4. The other surfaces extend between the two main side surfaces as a circumferential edge.

[0042] The engaging pawls 24 overlap profile parts characterized by reference sign 26, which are formed by extruded aluminum elements. The profile parts 26 are captively connected to the positioning frame 10 by the form-fit segments 22, 24. As usual, the engaging pawls 24 have a front ramp surface which expands the engaging pawls 24 when the profile parts 26 are pressed on and spring back against the outer surface of the insulating layers 8 after the profile parts 26 have been applied to engage behind the profile parts 26. In this way, the profile parts 26 are connected to the positioning frame 10. The insulating layers 8 are dimensioned such that they also fit between the form-fit segments 22, and if necessary are also latched in the manner described above, but in any case are clamped between the profile parts 26, which are held in a form-fit manner.

[0043] Accordingly, during assembly, a contact plate forming the strip conductor 6 is usually connected to the positioning frame 10 on one side, in this case by inserting the contact plate with its contact tongue into the lead-through opening of the upper cross beam 12. The form-fit segments 22 then embrace the strip conductor 6. The receptacle 18 is then closed on one side. The PTC element 4 is then inserted into this receptacle.

[0044] Then, for example, on the side provided with the strip conductor 6, the associated insulating layer 8 is applied against the corresponding strip conductor 6. The insulating layer is thereby arranged between the engaging pawls 24 or the form-fit segments 22, which ensure pre-positioning and retention of the insulating layer 8, which according to the embodiment is formed by a ceramic plate. Then, from the same side, the profile part 26 is applied against the positioning frame 10 and connected to the positioning frame 10 via the form-fit segments 22, 24.

[0045] On the opposite side, the other strip conductor 6, the insulating layer 8 associated with this strip conductor 6 and finally the profile part 26 provided there may then be mounted in the manner described above. Here too, before the profile part 26 is finally locked to the positioning frame, the positioning frame 10 holds the insulating layer 8 or the strip conductor 6 in a position favorable for assembly.

[0046] The PTC heating assembly 2 prepared in this way can be seen in FIG. 2 in the assembled state. In this embodiment, it is evident that only the form-fit segments 22 associated with the upper cross beam 12 are designed as engaging pawls. The form-fit segments 22 provided on the lower cross beam 14 merely overlap the profile parts 26.

[0047] In FIG. 2, to the right of the PTC heating assembly 2 a housing 100 of an electric heating device characterized by reference sign 98 in the Figures below can be seen. The housing 100 forms receiving pockets 102. One single PTC heating assembly 2 fits in each of the receiving pockets 102. The receiving pockets 102 are each configured like a hammerhead at the end, thus leaving space for the insertion of the form-fit segments 22, 24. In between, a structure of the receiving pocket 102, explained in more detail below, interacts with a structure provided on the outer surface of the profile parts 26 in order, on the one hand, to arrange the PTC heating assembly in the receiving pocket 102 with a certain pretension and thus with good heat-conducting properties, but, on the other hand, to prevent excessive stress on the elements of the PTC heating assembly 2 provided between the profile parts 26. The insulating layers 8 and the PTC element 4 are ceramic components and accordingly are only capable to a limited extent of compensating punctual stresses or bending stresses by elastic deformation.

[0048] FIG. 3 shows the essential components of the electric heating device 98 with a housing 100 made of a material with good thermal conductivity, in this case die-cast aluminum. The housing 100 forms a wall 105 circumferentially surrounding a heating chamber 104. In FIG. 2, the heating chamber 104 is still open at the bottom, since a bottom closing the housing 100 from underneath is not shown in FIG. 3. The same applies to a control housing cover which is connected to the housing 100 on the opposite side in order to cover and surround a connection chamber characterized by reference sign 106. The housing 100 forms a partition wall 108 between the heating chamber 104 and the connection chamber 106. Heating ribs 110 project from this partition wall 108 into the heating chamber 102. The heating ribs 110 are closed at their lower end projecting into the heating chamber 102. As illustrated by the hatching in FIG. 3, the heating ribs 110 together with the partition wall 108 and the wall 105 are formed from a one-piece die-cast aluminum housing 100.

[0049] The heating ribs 110 form a wedge-shaped downwardly tapering receiving pocket 102. The PTC heating assembly characterized by reference sign 2 is received in this receiving pocket 102. As the sectional view according to FIG. 4 illustrates, the PTC heating assembly 114 comprises a PTC element 116 at the main side surfaces of which strip conductors 118 abut, which in the present case comprises a wire mesh made of an electrically conductive material. On the side of the strip conductor 118 opposite the PTC element 116 is an insulating layer 120, which may be formed by a ceramic layer and/or an insulating plastic film. The gap between the insulating layer 120 and the PTC element 116 is filled overall by the strip conductor 118. For this purpose, the spaces between the wire mesh are filled with a good heat-conducting adhesive, which is also provided in the plane of the strip conductor 118 and is to be understood as belonging to the strip conductor 118. The wire mesh surmounts the PTC element to form contact tongues 122, which are shown in FIG. 3. Otherwise, the individual layers of the layered structure between the PTC element 116 and the profile part 126 have been combined in the form of a respective layer shown cut between the respective profile part 126 and the PTC element 116 for the sake of a clear presentation in FIG. 3.

[0050] The contact tongues 122 are exposed in the connection chamber 106. The PTC element 116 and the insulating layer 120 are joined into a single unit by adhesive bonding of the strip conductor 118. On the outside of this PTC heating assembly 114 compression elements 124 in the form of corrugated spring plates are provided, which can be seen in FIG. 4.

[0051] FIG. 4 shows details of the respective profile parts 126, which are configured identically in the present case. The compression elements 124 abut against the inner sides of these profile parts 126.

[0052] Groove limiting projections 132 project from the outsides of the profile parts 126 and enclose a groove 134 between them in pairs. As illustrated in particular by FIG. 4, a plurality of identically configured grooves 134 are recessed in this form on the outside of the main side surfaces of the profile parts 126. The grooves 134 extend in the insertion direction of the receiving pocket 102, which is characterized by E in FIG. 3.

[0053] An inner surface 136 of the receiving pocket 102 includes projecting tongue projections 138. These tongue projections 138 are integrally formed on the die-cast housing 100. As conveyed by the cross-sectional view shown in FIG. 4, the tongue projections 138 taper toward their free end in a wedge shape. In a corresponding manner, the groove limiting projections 132 are also configured to taper in a wedge shape toward their free front end. It is understood that only the surfaces of the groove limiting projections 132 respectively limiting the groove 134 have such a configuration. In order to illustrate this, the tongue projections 138 are omitted on the right side in FIG. 4.

[0054] In the embodiment shown in FIG. 4, the positioning frame 128 is first equipped with the PTC element 116, the strip conductors 118 and the insulating layers 120 as well as the compression elements 124 and the profile parts 126 during assembly. Then the PTC heating assembly 114 pre-assembled in this way is inserted into the receiving pocket 102. In the process, the tongue projections 138 engage in the grooves 134 associated with them. The result is a deformation in the region of the groove limiting projections 132, which can be seen from the comparison of the right-hand side with the left-hand side according to FIG. 4. This results in a certain tolerance compensation. In addition, the compression element 124 is deformed for tolerance compensation. Ideally, after assembly, the compression element 124 abuts essentially over its entire surface against the inner surface of the profile part 26 on the one hand and against the outside of the insulating layer 120 on the other.

[0055] The compression element 124 may be made of aluminum, copper, copper beryllium, or other material that has good thermal conductivity and applies permanently elastic pretensioning forces.

[0056] Any remaining cavities in the receiving pocket 102 can be filled by a good heat-conducting compound, such as a curing plastic compound filled with heat-conducting particles.

[0057] In the variant shown in FIG. 5, the groove limiting projections 132 are connected to the remaining profile part 26 via a relatively thin web 140. This web 140 provides a pivot axis that extends substantially in the insertion direction E. In this embodiment, compression elements may be omitted. Groove limiting projections 132 adjacent to different grooves 134 are spaced sufficiently far apart so that they can each pivot about their pivot axis when the wedge-shaped tongue projections 138 are inserted, without bumping against each other. This allows for considerable tolerance compensation. The layers of the PTC heating assembly 2 inside the profile parts 126 are thereby applied with good elastic tension against the inner surface of the two profile parts 126, which improves heat extraction.

[0058] FIG. 5 also illustrates the curvature of the inner surface of the profile parts 126 in such a way that, in a cross-sectional view, the profile part is essentially applied to the insulating layer 120 punctually and in a linear manner in the longitudinal direction. This deformation of the respective profile part 126 also causes additional elastic tensioning of the layers of the PTC heating assembly 114 in the receiving pocket 102.