DE102017223779A1 - Electric heating device and a method for producing the same - Google Patents

Abstract

The present invention relates to an electrical heating device, in particular for a motor vehicle, with heat-emitting elements (26) and a heat-generating element (30) and on heat-conducting elements (26) on opposite sides thereof, wherein the heat-generating element (30) has a positioning frame (2 ) and at least one PTC element (10), which is provided in the position frame (2), has main side surfaces (14) for the heat extraction and contact plates (18) of different polarity, said main side surfaces (24) of the position frame (2) a frame opening (16) leading to the PTC element (10) is provided. The present invention further relates to a method for producing an electrical heating device, in which at least one PTC element (10) is arranged in a position frame (2) at a distance from main side surfaces (24) of the position frame (2), into a frame opening (16). an electrically insulating mass (22) with good thermal conductivity is introduced which bridges the distance between one of the main side surfaces (24) and the PTC element (10), a heat-emitting element (26) is applied against the mass (22) and the mass ( 22) between the heat-emitting element (26) and the PTC element (10) is pressed and cured.

Description

The present invention relates to an electric heater, in particular for a motor vehicle, with heat-emitting elements and with a heat-generating element, which is thermally conductively connected at opposite main side surfaces with the heat-emitting elements and having a positioning frame and at least one PTC heating element, which is provided in the position frame and main side surfaces for the heat extraction. This PTC element is applied to contact plates of different polarity. The main side surfaces of the position frame are provided with a frame opening leading to the PTC element.

Such a prior art is for example from the EP 1 768 459 A1 known. In this prior art is located on opposite main side surfaces of the PTC element on a contact plate, which is provided on the outside with insulation. Against this isolation is a heat-emitting element in the form of a corrugated fin.

For a high efficiency of such electrical heating devices, it is essential that the heat is coupled out reliably and with good conductivity from the PTC element. Contact resistances at phase boundaries of different layers can impair such a good heat transfer. Thus, the experts endeavor to improve electrical heating devices of the type mentioned in that the heat emitted from the PTC element heat is coupled out as possible.

The present invention is based on the problem to provide an electric heater and a method for producing such, which can be operated with good efficiency, the method should be simple and reliable feasible.

To solve the device-related aspect, the present invention proposes an electric heating device having the features of claim 1. This differs from the aforementioned prior art in that in the frame opening an electrically insulating mass with good thermal conductivity is introduced, which bridges the distance between the heat-generating element and the PTC element or the contact sheet.

The present invention is based on the consideration that the positioning frame prescribes a receiving space that can be filled with the electrically insulating mass in the liquid or viscous state. This receiving space is at least laterally, possibly also completely surrounded by the positioning frame. The position frame can form a corresponding receiving space for both main side surfaces of the PTC element. The PTC element is usually located in the height direction centered in the position frame. In this case, the position frame due to its design can specify a PTC recording or a plurality of PTC images for the predetermined positioning of a plurality of PTC elements within the position frame. The PTC images usually specify the position of a PTC element in a form-fitting manner within the position frame.

The PTC element can be contacted with a contact plate on the front side. In this embodiment, the contact plate is not on a main side surface of the PTC element, but on a front side, the main side surface circumferentially surrounding edge surface of the PTC element. Thus, the heat-emitting surface of the PTC element is at least partially exposed within the frame opening. In this case, the electrically insulating compound is filled against the surface of the PTC element. Accordingly, the PTC element forms the lower boundary of the frame opening. In a more conventional energizing, in which the contact plate rests on a main side surface of the PTC element, the contact plate bounded on the underside of the frame opening and is wetted with the electrically insulating compound on the opposite side of the PTC element.

The electrically insulating mass extends from the interior of the position frame, i. H. the surface of the PTC element and / or the contact plate to the outside, usually up to an outer surface of the position frame. In this case, the electrically insulating compound is preferably applied before or during curing already against the surface of the heat-emitting element provided there, so that the electrically insulating compound sets in the preferred curing of the electrically insulating mass against the heat-emitting element and this with good thermal conductivity with the PTC Element coupled and beyond a unit of heat-emitting element and heat-generating element is formed. It is understood that this unit comprises two heat-emitting elements which abut on opposite main side surfaces of the positioning frame and which are preferably joined together in this way together with the heat-generating element.

The heat-generating element does not have to be formed symmetrically in the height direction, with the PTC element in the axis of symmetry extends. Such an embodiment is to be preferred. However, it may nevertheless first be prepared a position frame with one or more PTC elements, which already forms on one side of a core or insert of a good thermal conductivity material, for example, provided with an electrically insulating material, against the heat-emitting element at this Side of the position frame is glued. From the opposite side, for example, a PTC element can optionally be applied with the associated contact plate against such a layer of electrically insulating material. This is then followed by filling the opposite frame opening with the insulating mass.

However, it is preferable to receive the PTC element centrally in the height direction in the positioning frame, so that mutually opposite frame openings are formed by the positioning frame, which are respectively filled with the electrically insulating mass in the manner described above.

The space bridged by the mass extends in the height direction and thus in a direction perpendicular to the extension of the main side surface of the PTC element and the position frame. As a rule, almost the entire main side surface of the PTC element is wetted or covered by the mass.

The electrically insulating compound is preferably an addition-crosslinking two-component polymer, for example a correspondingly crosslinking silicone. The polymer should be resistant to hydrolysis. Important is a good thermal conductivity of at least 2 W / (m K). The composition preferably has a thermal conductivity of 3, more preferably 5 W / (m K). In view of this, the mass is usually added to a filler. These fillers are particles with good thermal conductivity, which, however, have electrically insulating properties. For example, particles of alumina may be used as filler. It can be gas or water atomization particles. To be preferred is a filler content of at least 50% by volume, more preferably between 85% by volume and 95% by volume. Although such a proportion of filler allows a very good thermal conductivity, but does not hinder the basically molten processing of the electrically insulating mass.

As filler, flakes are preferably used, d. H. Particles with irregular geometry and a considerable particle size distribution. Such a property of the filler content improves the dense placement of the filler within the liquid phase. The particles can interlock well and have direct contact with each other, which has a favorable effect on the heat transport through the mass.

When using a two-component polymer as a mass, the filler fraction with good thermal conductivity is preferably admixed before mixing the components of each individual component. This improves the degree of mixing of the resulting electrically insulating material.

The composition should also have a good dielectric strength of at least 10 kV / mm, more preferably at least 20 kV / mm. The specific breakdown resistance should be at least 1.9 × 10 ¹⁵ Ω / cm. The CTI value relevant for tracking resistance should be CTI> 600.

The electrically insulating mass may be formed so that the two components crosslink at room temperature. Such crosslinking is known to be accelerated with increasing temperature. In this case, the PTC element can be energized to crosslink the electrically insulating material and thereby heat is generated in the interior of the product to be produced. In this case, the PTC element is usually operated with a voltage below the operating voltage. Important for a controlled hardening of the electrically insulating compound without blistering is the best possible heating. The temperature inside must not rise too fast. Thus, the stress for hardening the mass is set to a value which is below the actual operating point. For example, in a heat generating element operated at high voltage, for example, 350 V, the voltage for heating may be 200V.

The curing is preferably carried out with a stamp, by which the electrically insulating compound is not only pressed in the frame opening, but is also cured. This stamp can bear directly against the electrically insulating compound or with the interposition of the heat-emitting element or a part thereof. In this case, the compressive stress is also used to connect the heat-emitting element well with the heat-generating element and to secure the connection permanently by curing the electrically insulating mass. It can be smoothed before curing the electrically insulating material and after the introduction of the same in the frame opening to remove excess material and to even out the surface, so that the heat-emitting element can be applied over the entire surface of the electrically insulating mass to the heat-generating element. The stamp is preferably heated or heated before or during the pressing.

According to a preferred development of the present invention, the positioning frame has the PTC element protruding on both sides. These projections prevent direct contact between the heat-emitting, usually made of metal element and the electrically conductive parts of the heat-generating element. The protrusions ensure a minimum clearance that is filled with the electrically insulating mass. The corresponding contact surface is usually formed by pins which project beyond the PTC element on both sides. The PTC element can be surmounted in each case by a plurality of pins on its opposite main side surfaces, so that the PTC element is fixed in position in the direction of the frame opening between the pins within the position frame in a form-fitting manner. The pins have an extension in the longitudinal direction of the usually elongated frame, which is preferably less than the longitudinal extension of the PTC element. This consideration assumes that the material forming the position frame has a poorer thermal conductivity than the electrically insulating mass, so that the area ratios of the position frame forming material within the frame opening, ie, the space between the main side surface of the PTC element and the associated heat emitting element should be filled as possible with the electrically insulating mass. Against one of the pins, the heat-generating element can lie directly or with the interposition of the mass.

The method for solving the above problem with the present invention provides for arranging at least one PTC element in the positioning frame and at a distance from the main side surfaces thereof. Thereafter, the frame opening is filled with an electrically insulating material with good thermal conductivity. This mass is introduced into the frame opening in such a way that the distance between the main side surface and the PTC element is bridged. This distance is predetermined either by the surface of the PTC element itself or by a contact plate resting against this surface. The statements made to the device claim insofar here apply accordingly.

Thereafter, a heat-emitting element is applied against the mass, which may also be applied against parts, in particular projections of the position frame, in order to maintain the necessary distance to the PTC element. Thereafter, the mass is cured by applying an external force against the heat-emitting element. Thus, the heat-emitting element is connected during curing of the mass against the PTC element with the interposition of the mass with the heat-generating element.

Further details and advantages of the present invention will become apparent from the following description of an embodiment in conjunction with the drawings.

• 1 eine perspektivische Schnittansicht eines Ausführungsbeispiels eines wärmeerzeugenden Elementes;
• 2 eine perspektivische Schnittansicht gemäß der Darstellung in 1 für ein Ausführungsbeispiel eines Heizstabes; und
• 3 das in 1 gezeigte Ausführungsbeispiel bei einer Draufsicht.

In this show:

• 1 a sectional perspective view of an embodiment of a heat generating element;
• 2 a sectional perspective view as shown in FIG 1 for an embodiment of a heating element; and
• 3 this in 1 shown embodiment in a plan view.

The 1 shows a position frame 2 by two parallel extending frames 4 is formed. As 3 has each of the positioning frame bars 4 in the longitudinal direction of the strips 4 spaced-apart projections 6 , in the height direction (see. 1 ) are provided one above the other so that they have a PTC recording 8th for a with reference number 10 form a labeled PTC element. In the PTC recording 8th is the PTC element 10 in the height direction H held positively. As 3 reveals the PTC element 10 in the longitudinal direction of the position frame strips 4 the individual projections 6 , Between individual PTC elements 10 Present in the longitudinal direction of the position frame 2 are provided one behind the other in a plane, there is a gap 12 that the two adjacent PTC elements 10 spaced apart.

Beyond the tabs 6 is the clear transverse distance of the two position frame strips 4 so chosen that a main side surface 14 of the PTC element 10 completely in one with reference numerals 16 marked frame opening is exposed. In the embodiment shown, the main side surfaces 14 the PTC elements 10 with contact plates 18 contacted, at least one side over the position frame 2 in the longitudinal direction L are extended to form contact tongues for the electrical connection of the electric heater. The corresponding contact sheets 18 are energized with different polarity, that is connected after connection to a power supply to cable paths within the vehicle of different polarity. This connection can take place with the interposition of a control device, which is integrated in a frame, which is preferably made of plastic and an outer enclosure of a single, in 2 shown and with reference numerals 20 characterized heating rod or more of such heating elements 20 can be. As a result, a structural unit of the or the heating elements 20 and reaches the control device via the frame.

The 1 shows one in the opposite frame openings 16 filled electrically insulating mass 22 after this mass 22 on a main side surface 24 of the position frame was smoothed. The electrically insulating mass 22 extends to the contact plates 18 , The crowd 22 surpasses the position frame 2 not in the vertical direction. The crowd 22 Ends flush with the surface of the frame 2 ,

In 2 is the heating element 20 presented after completion. Both sides against the main side surface 24 of the position frame 2 are heat-emitting elements 26 intended. These corrugated ribbed layers 26 consist of one, possibly of several metal strips. At least one of the metal strips is meandering for the formation of corrugated ribs 28 of the heat-emitting element 26 umbogen. Preferably, these corrugated ribs 28 with its vertex directly against the main side surface 24 of the position frame 2 on. They are completely or partially immersed in the electrically insulating material. The corrugated ribs 28 can also be used against a metal strip of the heat-emitting element 26 abutment, between the vertices of the individual corrugated ribs and the main side surface 24 of the position frame 2 or the surfaces of the projections 6 is provided. In this case, the heat-emitting element 26 full surface with the electrically insulating mass 22 connected.

The connection takes place for example after placing the heat-emitting layers 26 against the opposite main side surfaces 24 of the position frame 2 , Thereafter, from the outside against the respective heat-emitting elements 26 pressed. These displace some of the not yet cured electrically insulating mass 22 , if necessary, until the heat-emitting elements 26 against the projections 6 bump. This is the end position of the heat-emitting elements 26 specified. There will be a minimum distance between the heat-emitting elements 26 and the electrically conductive parts of a with reference numerals 30 designated heat generating element created. The heat-generating element 26 in the present case consists of the PTC elements 10 , the contact plates on both sides 18 and the position frame 2 as well as the therein filled and finally cured electrically insulating mass 22 , The outside against the heat-emitting elements 26 Wholly or partially applied stamp is preferably heated, so that the electrically insulating mass 22 accelerates hardening. In addition, the heat-generating element 30 be energized to the in 2 to heat shown electric heater inside and thus to accelerate the curing process.

As the 1 and 2 clarify, lie the projections 6 with its outer surface below the main side surface 24 of the position frame 2 given level. The heat-emitting elements 26 are slightly narrower than the transverse distance of the position frame strips 4 in the plane of the main side surface 24 of the position frame 2 , This is how the heat-emitting elements become 24 through the position frame 2 also in width or transverse direction B of the position frame. The heat-emitting elements 26 are thereafter at the heat generating element 30 glued, however, also held positively.

The figures only show a section of the heat-generating element 30 or the heating rod 20 longitudinal. When filling with the electrically insulating material 22 usually overhang the contact sheets 18 with it by punching integrally formed contact tongues the position frame 2 on one side. On the other side, the position frame towers over 2 the ends of the contact sheets. There, the remaining space is also with the electrically insulating mass 22 filled to a bottom-side conclusion of the heat-generating element 30 reach and seal the contact plates and the PTC elements end. On the opposite side, there is a corresponding filling with release of the contact tongues, so that the heat-generating element can be easily connected electrically.

LIST OF REFERENCE NUMBERS

2

position frame

4

Positioning frame bar

6

head Start

8th

PTC recording

10

PTC element

12

gap

14

Main side surface of the PTC element

16

frame opening

18

contact sheet

20

heater

22

electrically insulating mass

24

Main side surface of the position frame

26

heat-emitting element

28

corrugated fin

30

heat generating element

H

height direction

B

width direction

L

length direction

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1768459 A1 [0002]

Claims (10)

An electric heating device, in particular for a motor vehicle, having heat-emitting elements (26) and a heat-generating element (30) and heat-emitting elements (26) in thermal conduction on opposite sides thereof, wherein the heat-generating element (30) comprises a positioning frame (2) and at least one PTC Element (10) provided in the positioning frame (2), having main side surfaces (14) for heat extraction and abutting contact plates (18) of different polarity, wherein main side surfaces (24) of the position frame (2) with a to the PTC Element (10) leading frame opening (16), characterized in that in the frame opening (16) an electrically insulating mass (22) is introduced with good thermal conductivity, the distance between the heat-emitting element (26) and the PTC Bridged element (10) or the contact plate (18). Electric heater after Claim 1 , characterized in that the position frame (2) the PTC element (10) on both sides protruding projections (6) forming the contact surfaces for the heat-emitting elements (26). Electric heater after Claim 1 or 2 , characterized in that the position frame (2) on both sides of the PTC element (10) has frame openings (16), in each of which the electrically insulating mass (22) is introduced, the distance between the heat-emitting elements (26) and the PTC Element (10) or the associated contact plate (18) bridged. Electric heating device according to one of the preceding claims, characterized in that the positioning frame (2) by two parallel extending strips (4) is formed, which receive a plurality of PTC elements (10) and adjoining contact plates (18) and the above the electrically insulating mass (22) are interconnected. Method for producing an electrical heating device, in which at least one PTC element (10) is arranged in a position frame (2) at a distance from main side surfaces (24) of the position frame (2), an electrically insulating mass (22 ) having good thermal conductivity bridging the distance between one of the main side surfaces (24) and the PTC element (10), a heat-emitting element (26) applied against the mass (22) and the mass (22) between the heat-emitting element (26) and the PTC element (10) is pressed and cured. Method according to Claim 5 , characterized in that the mass (22) after the introduction of the mass (22) in the frame opening (16) is smoothed. Method according to Claim 5 or 6 , characterized in that the mass (22) is a crosslinking plastic mass which is cured by applying heat. Method according to one of Claims 5 to 7 , characterized in that the mass (22) is pressed by a heated punch whose heat input accelerates the hardening of the mass (22). Method according to one of Claims 5 to 8th , characterized in that the mass (22) comprises an addition-crosslinking two-component polymer, wherein each of the components before the mixing of the components, a filler with good thermal conductivity is mixed. Method according to one of Claims 5 to 9 , characterized in that the mass (22) is admixed with a filler of irregular geometry and grain size.

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