PTC Heating Cell

Abstract

A PTC heating cell has a cuboid-shaped PTC element and two metallizations electrically separated from each other and provided on the surface of the PTC element for the introduction of current to the PTC element. The two metallizations are provided as strips formed over an entire longitudinal extension (L) of the PTC element on diagonally oppositely disposed surface sections of the PTC element.

Claims

1. A PTC heating cell comprising: a cuboid-shaped PTC element, and two metallizations that are electrically separated from each other and that are provided on a surface of the PTC element for the introduction of current thereinto, wherein the two metallizations are provided as strips formed over an entire longitudinal extension (L) of the cuboid-shaped PTC element on diagonally oppositely disposed surface sections of the cuboid-shaped PTC element.

2. The PTC heating cell according to claim 1, wherein the strips have a width (b) of less than half a width of the cuboid-shaped PTC element.

3. The PTC heating cell according to claim 1, wherein the strips extend in a width direction (B) of the cuboid-shaped PTC element up to an adjacent edge of the cuboid-shaped PTC element.

4. The PTC heating cell according to claim 3, wherein the strips extend in a longitudinal direction of the cuboid-shaped PTC element from edge to edge.

5. The PTC heating cell according to claim 1, wherein two contact rails extend in a longitudinal direction of the cuboid-shaped PTC element, each of which is respectively associated with one metallization.

6. The PTC heating cell according to claim 5, wherein each of the the contact rails are formed to be U-shaped and clamps the cuboid-shaped PTC element and the associated metallization between them.

7. The PTC heating cell according to claim 5, wherein each of the contact rails has a spring projection that is formed integrally thereon and that abuts against the associated metallization under resilient pretension.

8. The PTC heating cell according to claim 5, further comprising an injection mold coating which is made of an insulating plastic material, which surrounds the contact rails and which leaves heat-dissipating surfaces of said the cuboid-shaped PTC element free.

9. The PTC heating cell according to claim 5, wherein surfaces of the cuboid-shaped PTC element that are not provided with the metallization are covered with an insulating layer.

10. The PTC heating cell according to claims 9, wherein each contact rail and the injection mold coating engage over a longitudinal edge of the insulating layer.

11. The PTC heating cell according to preceding claim 5, wherein area portions of the oppositely disposed main side surfaces of the cuboid shaped PTC element that are not provided with the metallization are covered with an insulating layer.

12. The PTC heating cell according to claims 5, wherein each contact rail and the injection mold coating engage over a longitudinal edge of the insulating layer.

13. The PTC heating cell according to claim 8, wherein the injection mold coating engages over a longitudinal edge of the insulating layer.

14. The PTC heating cell according to claim 2, wherein the strips have a width (b) of less than a quarter of the width of the cuboid-shaped PTC element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention shall be explained schematically below using an embodiment in conjunction with the drawing, in which:

[0021] FIG. 1 shows a perspective face side view of a PTC heating cell;

[0022] FIGS. 2A and 2B show two variants for contact rails for electrically contacting the embodiment; and

[0023] FIG. 3 shows a sectional view of the edge region of the embodiment with an injection mold coating.

DETAILED DESCRIPTION

[0024] FIG. 1 shows a cuboid-shaped PTC element 2. The longitudinal direction is marked as L, the width direction as B and the thickness direction as D. Oppositely disposed main side surfaces 4 span the width direction B and the longitudinal direction L. Strip-shaped metallizations 6 are provided on the edge of each main side surface 4. They extend in the longitudinal direction L from edge to edge. In the width direction B, the metallizations 6 each start at the edge which laterally defines the main side surface 4. The metallization 6 has a rectangular cross section and is applied to the ceramic main side surface 4 by sputtering. The two metallizations 6 are configured identically and associated with oppositely disposed longitudinal edges. The polarities of the metallizations 6 are marked as +and −. Arrows within the PTC element 2 illustrate the current path through the PTC element 2. In the embodiment shown, the width b of the strip 6 corresponds to approximately 20% of the width B of the PTC element 2.

[0025] Contact with the power current es established by way of two contact rails 10 which are shown by way of example in FIGS. 2A and 2B. The respective contact rails 10 are U-shaped in cross section with oppositely disposed legs 12 which are connected to one another by a web 14. Spring projections 16 formed by punching and bending project from the inner surfaces of the legs 12. They form ramp surfaces in the embodiment according to FIG. 2 and ascend in the longitudinal direction of the contact rail 10 and therefore in the longitudinal direction and thus enable the PTC element to be introduced in the direction of the arrow P. In the embodiment according to FIG. 2B, the ramp surfaces are provided at a right angle thereto, so that the PTC element 2 can be pushed in the width direction in between the legs 12. The legs 12 abut with their spring projections 16 against the PTC element 2. The spring projections abutting against the metallization 6 are used for introducing the power current via the contact rail 10, whereas the oppositely disposed legs 12 are only used for mechanical attachment. Since a metallization and therefore an electrode is lacking there on the surface of the ceramic PTC element 2, there is no introduction of the power current there

[0026] FIG. 3 shows a sectional view for a variant in which an insulating layer 18 in the form of a ceramic plate or a plastic film is placed on the region of the main side surface 6 that is not provided with the metallization 6. The legs 12 of the contact rail 10 engage over the edge region of the insulating layer 18 extending in the longitudinal direction L which is accordingly mechanically secured. FIG. 3 also illustrates an injection mold coating, denoted with reference numeral 20, made of insulating plastic material which engages over the contact rail 10 as well as an extended edge region of the insulating layer 18 and seals the contact rail 10. The outer surface of the insulating layer 18 therefore forms the heat-dissipating outer surface of the PTC heating cell. The latter can be introduced directly as a heating element into an electric heating device of a motor vehicle for heating a liquid or gaseous medium.