WO2007097721A2

WO2007097721A2 - Heating body

Info

Publication number: WO2007097721A2
Application number: PCT/SI2007/000003
Authority: WO
Inventors: Davorin Rejc; Iztok Skocir; Janez Urbas
Original assignee: Aet Druzba Za Proizvodnjo Vzignih Sistemov In Elektronike D.O.O.
Priority date: 2006-02-22
Filing date: 2007-01-16
Publication date: 2007-08-30
Also published as: SI21985A

Abstract

The invention relates to the structure of a heating body of an electric heater for airflow heating, particularly suitable for heating automotive passenger compartments. The radiating elements of the electric heater are made of PTC (Positive Temperature Coefficient) ceramics. The inventive heating body has heating elements (7) and spacers (10) alternately inserted adjacent to the first of two opposite inner walls of the housing (6) of the heating body, whereas electrically insulating elements (5) are inserted adjacent to the second of the inner walls of the housing (6), and two contact lamellae (8, 9) are inserted between the heating elements (7) and the spacers (10) on one side and the insulating elements (5) on the other side. The heating elements (7) are made of PTC ceramics and are lamella-shaped, and fins are soldered to the heating bodies (3) in order to increase the surface of the heater. The heating bodies are made in such a way that heating elements (7) and spacers (10) are alternately inserted adjacent to two opposite inner walls of the housing (6) of the heating body (3), while two contact lamellae (8, 9) are inserted between opposite heating elements (7) . The lamellae (8) and (9) are provided with alternating holes (11) and noses (12) along their respective lengths.

Description

Heating Body

The invention relates to the structure of a heating body of an electric heater for airflow heating, particularly suited for heating automotive passenger compartments. The radiating elements of the electric heater are made of PTC (Positive Temperature Coefficient) ceramics.

The cabins of motor vehicles are generally heated by means of radiators powered by the hot cooling fluid from the vehicle engine. Recently, for reasons of comfort and air conditioning, additional electric heaters are progressively coming into use. Motor vehicle electric heaters must be small in size and, most importantly, safe. Electrical resistance heaters are not appropriate for this purpose as they involve elevated temperatures and the employment of relatively unreliable thermal switches. The most suitable heating element has turned out to be PTC ceramics which increases its resistance at higher temperatures, thereby reducing the heating power and automatically regulating the temperature of the heating element. The overheating of the heater and the related hazards are thus reduced to a minimum. However, the use of PTC ceramics for producing heating elements presents new constructional challenges, particularly as to achieving an engagement of the heating element and the housing that will be tight enough to ensure a good thermal and electrical contact.

Structures are known in the art having a heating element made of PTC ceramics, loaded by either a spring or a plastic deformation pushing it toward an electrically and thermally conductive surface, generally an aluminum panel or rectangular profile. In such cases the thermal contact and the electrical connection are provided by the engagement" of the heating element with the aluminum support, and elements such as fins are added to the aluminum support in order to increase the surface thereof. The pressure of the heating element onto the support is provided by a spring pressing the heating element against the support and acting as the second electrical connection at the same time. Such solutions involving the use of a spring as well as solutions wherein the pressure of the heating element is achieved by means of a plastic deformation of a rectangular-profile pipe, with all the elements of the heating body embedded into the pipe •beforehand, are set forth in patent documents EP 1370117, US 5,256,857, and US 2003/0015520.

Two types of disadvantages are exhibited by prior art solutions: firstly, springs lose elasticity over time, thereby increasing the likelihood of a loosened engagement of the heating elements and the support, impairing, in turn, the dissipation of heat, and secondly, such structures require that the assemblage and the finalization of the heating bodies, i.e. the combination of the support, the heating elements and the springs, be performed beforehand, prior to assembling a plurality of heating bodies into a heater. This means that once it contains heating elements and springs, the heater can no longer be thermally treated. For reasons of better heat dissipation the heater should possess extensive surfaces, which is why the heating bodies should have ribs or fins. To achieve good thermal contact between the heating bodies and the fins, said fins should preferably be soldered to the heating bodies, which is only possible at elevated temperatures that would damage the previously embedded heating bodies.

The object of the invention is a heating body, structured so as to reduce the effects of aging and dynamic stresses of the spring elements, and provide for a simple way of assembling the heating elements of the heating body.

According to the invention, the object is achieved with a heating body of an automotive electric heater according to the independent patent claim.

The invention shall now be described with reference to an embodiment thereof and the accompanying drawings, representing:

Figure 1: A detail of the structure of the heating body; Figure 2 : A cross section of the structure of the heating body during the insertion of the elements;

Figure 3: A cross section of the structure of the heating body after the elements have been fixed.

The housing 6 of the heating body is a hollow rectangular metal profile, i.e. a rectangular pipe. Heating elements 7 and spacers 10 are alternately inserted adjacent to the first of two opposite inner walls of the housing 6. The heating elements 7 are made of PTC ceramics and are lamella-shaped. The spacers 10 are made of an electrically insulating material and shaped as a groove, so that the internal walls thereof abut against the three internal walls of the housing 6. Adjacent to the second of the two opposite inner walls of the housing 6, electrically insulating elements 5 are inserted. The insertion of the heating elements 7 and the spacers 10 on one side of the inner walls of the housing 6 and of the insulating elements 5 on the other side thereof is accompanied by the insertion of the first contact lamella 8 and of the second contact lamella 9 between the elements 7 and the spacers 10 and the opposite insulating elements 5. The lamellae 8, 9 are inserted into the grooves of the spacers 10 in such a manner that they can not make electrical contact with the housing 6. The lamellae 8, 9 are made of an electrically conductive material capable of elastic deformation. In accordance, with the embodiment shown herein, there are protruding noses 11 disposed along the longitudinal axis of the lamella 8, and corresponding holes 10 in the lamella 9. The step distance between consecutive noses 11 and consecutive holes 10 is the same, the spacing between consecutive holes 10 and noses 11 being such that there are at least two holes 10 and two noses 11 per heating element 7. While the heating elements 7 and the spacers 10 are being inserted into the interior of the housing 6, the lamellae 8 and 9 are mutually positioned in such a manner that the noses 11 of the lamella 8 engage with the holes 10 of the lamella 9. In said relative position the lamellae 8 and 9 fit closely together along their entire surface and length. Consequently, they present a small overall thickness, which is the sum of the respective thicknesses of both the lamellae 8 and 9. After inserting the elements 7, the spacers 10 and the insulating elements 5 into the housing 6, one of the lamellae, say the first lamella 8, is partially pulled out, so that the noses 11 of the lamella 8 are lifted out of the holes 10 of the lamella 9 and lean against the surface of the lamella 9. The reciprocal distance and, consequently, the overall thickness of the lamellae 8 and 9 is thereby increased for the height of the noses 11. The lamellae 8 and 9, in turn, press against the heating elements 7. Thus, the heating elements 7 come into close electrical and thermal contact with the wall of the housing 6 and into electrical contact with the lamellae 7 and 8. The respective lengths of the lamellae 8 and 9 are different enough to allow for a grip of the lamellae 8 and 9 prior to the extraction. After the extraction, both ends of the lamellae are resistance welded to one another in order to prevent the lamellae from possibly returning to their original position (s). Both ends of the lamellae 8 and 9 thus jointly constitute an electrical connection, the other electrical connection being represented by the housing 6.

It is self-evident and within the scope of the present invention that the holes and noses may be disposed arbitrarily along the lamellae, viz. there may be both holes and noses on the same lamella, as long as the noses of the first lamella correspond to the holes of the second lamella and, vice versa, the holes of the first lamella correspond to the noses of the second lamella. In Figures 2 and 3 the fins are also shown which are employed to enlarge the heating area of the heater and which are disposed over the housing 6.

Therefore, the heating body of the invention does not include springs or plastically deformed elements and provides for simple insertion of the heating elements, the lamellae and the spacers after the fins have been soldered to the housings of the heating bodies. A quality and permanent electrical and thermal contact is thus ensured, as well as a simple method of assembling.

Claims

Patent Claims

1. Heating body of an electric heater for heating automotive passenger compartments, wherein the heating elements are made of PTC ceramics and wherein the heater has fins mounted over the heating bodies to increase the area of the heater, characterized in that heating elements (7) and spacers (10) are alternately inserted adjacent to the first of two opposite inner walls of the housing (6) of the heating body, whereas electrically insulating elements (5) are inserted adjacent to the second of the two opposite inner walls of the housing (6), and two contact lamellae

(8, 9) are inserted between the heating elements (7) and the spacers (10) on one side and the insulating elements (5) on the other side.

2. Electric heater according to Claim 1, characterized in that the two lamellae (8) and (9) are provided with alternating holes (10) and noses (11) along their respective longitudinal axes.

3. Electric heater according to the preceding claims, characterized in that the step distance between consecutive holes (10) and noses (11) is such that there are at least two holes (10) and two noses

(11) per each heating element (7) .

4. Electric heater according to the preceding claims, characterized in that the two lamellae (8, 9) are electrically conductive and constitute one of the electrical connections of the heater.