Heating device

Abstract

Disclosed is a heating device comprising a plate-shaped ceramic PTC resistor having a thickness, a front side, a back side and narrow sides, wherein the distance from the front side to the back side equals the thickness, and a first contact element and a second contact element, which are electrically contacting the PTC resistor. The PTC resistor is electrically contacted by the contact elements on opposite narrow sides.

Claims

1. A heating device, comprising: a plate-shaped ceramic PTC resistor having a thickness, a front side, a back side and narrow sides, wherein the distance from the front side to the back side equals the thickness; a first contact element electrically contacting the PTC resistor on a first one of the narrow sides; and a second contact element contacting the PTC resistor on a second one of the narrow sides opposite the first narrow side.

2. The heating device according to claim 1, comprising an electrically isolating frame holding the PTC resistor and the contact elements.

3. The heating device according to claim 2, wherein the contact elements are embedded in the frame.

4. The heating device according to claim 3, wherein the contact elements are embedded in the frame by insert molding.

5. The heating device according to claim 1, wherein the PTC resistor comprises a plurality of plate-shaped ceramic PTC resistors arranged in a row and electrically contacted on opposite narrow sides thereof.

6. The heating device according to claim 1, comprising a tube in which the ceramic PTC resistor and the contact elements are arranged.

7. The heating device according to claim 1, wherein the electrical contact elements are formed of strips of sheet metal.

8. The heating device according to claim 7, wherein the contact elements comprise bent rim sections that electrically contact the PTC resistor.

9. The heating device according to claim 1, wherein the electrical contact elements press resiliently against the narrow sides of the PTC resistor.

10. The heating device according to claim 1, wherein the narrow sides of the PTC resistor are covered by a metallic layer.

11. Air heater comprising several rod-shaped heating devices according to claim 1, wherein the rod-shaped heating devices are arranged side by side and cooling fins are arranged between neighboring rod-shaped heating devices.

12. The heating device according to claim 1, wherein the heating current is configured to flow across the width of the PTC resistor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

(2) FIG. 1 shows an electrical heating device;

(3) FIG. 2 shows a frame holding contact elements and several PTC resistors;

(4) FIG. 3 shows another view of the arrangement of FIG. 2;

(5) FIG. 4 shows a detail of FIG. 3; and

(6) FIG. 5 shows a sectional view to FIG. 3.

DESCRIPTION

(7) The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.

(8) FIG. 1 shows a heating device for heating the interior of the passenger compartment of a vehicle. The heating device shown in FIG. 1 is an air heater comprising several heating rods 1 and cooling fins 2 connected to the heating rods 1. The heating rods 1 are arranged side by side and cooling fins 2 between them. The ends of the heating rods 1 are held by holders 8, 9.

(9) The heating rods 1 may comprises tubes, e.g., flat tubes, in which plate-shaped PTC resistors made of a ceramic based on barium titanate are arranged. The tubes of the heating rods may be made of metal, e.g., an aluminum based alloy. FIGS. 2 and 3 show an illustrative example of an isolating frame 6 holding several plate-shaped PTC resistors 3 and electrical contact elements 4. FIG. 4 shows a detail of FIG. 3, namely an end of the frame 6 and the contact elements 4 together with one of the PTC resistors 3. FIG. 5 shows a cross section of the frame 6 with contact elements 4 and PTC resistor 3.

(10) The plate-shaped PTC resistors 3 each have a front side 31, a back side 32 and narrow sides 33, 34. The distance between the front side 31 and the back side 32 is the thickness of the plate-shaped PTC resistor 3. The distance between opposite narrow sides 33, 34 is the width of the plate-shaped PTC resistor 3.

(11) The plate-shaped PTC resistors 3 are electrically contacted by the contact elements 4 on opposite narrow sides 33, 34. Thus heating current flows through the PTC resistors 3 within the plane defined by the plate-shaped PTC resistor 3 across the width of the PTC resistor 3. In contrast to conventional designs wherein heating current flows from a front side to a back side of a plate-shaped PTC resistor in the thickness direction of the plate-shaped PTC resistor, the electrical resistance provided by the plate-shaped PTC resistor 3 contacted at opposite narrow sides is much larger. Heating currents are thereby advantageously reduced even if high voltages are applied to the contact elements 4.

(12) The contact elements 4 are embedded in the frame 6, e.g., by insert molding. The contact elements 4 may be provided as strips of sheet metal such that each contact element 4 electrically contacts several plate-shaped PTC resistors 3 arranged in a row and held by the frame 6.

(13) The PTC resistors 3 may be clamped between the contact elements 4. For example, the contact elements may be metal strips with bent off rim sections 41 that press resiliently against the narrow sides of the PTC resistors 3 and form contact tongues. Clamping forces may be reduced as necessary by cutting out parts of the bent rim section 41.

(14) The narrow sides 33, 34 of the PTC resistors 3 contacted by the contact elements 4 may be covered by a metallic layer in order to improve the electrical contact between the contact elements 4 and the PTC resistors 3.

(15) Heat generated by the PTC resistors 3 is transferred to a tube of a heating rod 1 via the front and back sides 31, 32 of the PTC resistors 3. The PTC resistors 3 can be electrically isolated from a surrounding tube by isolating layers covering the front and back sides 31, 32, e.g., layers of ceramic material like alumina. Flat tubes may be compressed to improve thermal contact after the frame 6 with PTC resistors 3, contact elements 4 and isolating layers are arranged therein. Compressing the flat tubes makes them flatter and causes pressure on the front and back sides 31, 32 of the PTC resistors 3.

(16) While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

LIST OF REFERENCE SIGNS

(17) 1 heating rod 2 cooling fin 3 PTC resistor 4 contact element 6 frame 8 holder 9 holder 31 front side 32 back side 33 narrow side 34 narrow side 41 bent rim section