EP2109347A1 - Electric device for heating, in particular a motor vehicle - Google Patents

Abstract

The device has a contact layer (35) arranged in a contact region between an electrical heating unit (2) and an electrical contact device. A balancing unit (12) balances mechanical voltages in the contact region of the electrical heating unit and the electrical contact device. The balancing unit is formed by an adhesive agent (37) i.e. chromium, which is arranged between the contact layer and the electrical heating unit. A reduction unit (39) is formed by an intermediate layer (36) that is arranged between the contact layer and the adhesive agent.

Description

The invention relates to an electrical device for heating, in particular of a motor vehicle, with an electric heating device, with an electrical contact device and with a contact coating, which is arranged in a contact region between the electric heating device and the electrical contact device.

Such electric heaters are used more consistently in motor vehicles to support, for example, a regular main heating a passenger compartment of a motor vehicle, if they can not win a sufficient heat such as from a coolant circuit of an internal combustion engine of the motor vehicle. This may be the case in particular in a starting phase of the internal combustion engine. Even at very low outside temperatures can by means of such an electrical Heating device can be advantageously provided an additional heating power.

In particular, in fuel-efficient motor vehicles, regular main heating systems for heating passenger compartments are being developed further, since consumption-optimized motor vehicles often can no longer provide enough waste heat from an internal combustion engine, which can be treated by means of a regular main heating to heat a passenger compartment. This is particularly noticeable at low ambient temperatures or outside temperatures, so that often also here a heating with at least temporarily used additional Zuheizvorrichtungen is required in order to provide a desired climate comfort in the passenger compartment quickly. Especially during a warm-up phase of an internal combustion engine, in a low load operation of an internal combustion engine, for example in city traffic, and / or in an idle mode of an internal combustion engine, a requested heating demand with the regular main heating of the motor vehicle can often not be sufficiently covered.

In order to at least be able to reduce such a heating deficit, various possibilities are already provided to support the regular main heating, for example by means of fuel heaters, electrical auxiliary heaters for coolant of the main heater (coolant side heater) or for a ventilation air (air side heater), exhaust heat exchanger, etc. By such Zuheizvorrichtungen a comfortable interior temperature in a passenger compartment advantageously can be achieved faster. In addition, the electric Zuheizvorrichtungen also allow faster defrosting of ice sheets on a windshield of a motor vehicle.

An electric heater with respect to a ventilation air for a passenger compartment proves to be the most sensible of these options, since suitable electrically operated heaters, such as PTC elements, also directly in one of the passenger compartment supplied ventilation air flow can be arranged so that the ventilation air immediately warm well and noticeably.

Such PTC elements often consist of a ceramic and are already well known in the art. In the case of a PTC ceramic, the resistance of the PTC ceramic element increases very sharply with increasing temperature. As a result, a very uniform surface temperature at the PTC ceramic element can advantageously be set independently of further boundary conditions, such as, for example, an applied voltage, a nominal resistance of the amount of ventilation air supplied to the PTC ceramic element. Thus, overheating of the PTC ceramic element and surrounding components can be successfully prevented, as could easily arise, for example, when using simple heating wires. Also, an electrical fuse is not required because the PTC ceramic element can self-regulate by its own behavior as a PTC thermistor. Specifically, as the temperature increases, the electrical resistance in the PTC ceramic increases proportionally, allowing less electrical energy to flow through the PTC ceramic, thereby allowing less heat to develop within the PTC ceramic.

A disadvantage of such PTC ceramic elements, which can be used this year as electrical heaters, is that they are relatively expensive and thus contribute significantly to high production costs of an electric Zuheizvorrichtung. In addition, one is relatively limited in the shaping or in the selection of the achievable geometry of the PTC ceramic elements. In general, have standardized PTC ceramic elements Dimensions ranging from 6 mm to 15 mm wide x 20 mm to 40 mm deep with a thickness of 0.8 mm to 2 mm.

The structural design of electric Zuheizvorrichtungen based on such PTC ceramic elements is almost always very similar. The PTC ceramic elements can each be contacted from both sides with a contact plate, such as aluminum, in order to be able to improve electrical contact with the respective PTC ceramic element. On a side facing away from a first PTC ceramic element side of a contact plate beyond a corrugated fin can be arranged, which can be followed by another contact plate of another PTC ceramic element. Thus, between two adjacent contact sheets of two PTC ceramic elements, for example, a corrugated fin with or without reinforcement can be provided as a heat transfer network, by means of which a heat transfer from the PTC ceramic element to the ambient air or to a ventilation air can be facilitated. Components of such a constructed electric Zuheizvorrichtung can be clamped together either by means of a spring or by means of several springs or glued together by means of suitable adhesive connections.

Especially with smaller PTC Zuheizvorrichtungen without additional corrugated fins as a heat transfer network, for example, for direct installation in air ducts or air outlets of a motor vehicle heating, it is usually also possible that the entire heat exchanger network consists of individual PTC ceramic elements having a plurality of holes or recesses through which a ventilation air to be heated can flow directly through. Dimensions of such PTC ceramic elements can also be about 40 mm to 100 mm wide x 30 mm to 80 mm deep with a thickness of 8 mm to 20 mm. However, these rather large PTC ceramic elements are even more costly than the aforementioned smaller PTC ceramic elements. In addition, they are much heavier, making the electric heater is difficult to build.

Not least because of the good decentralized arrangement options, the proportion of ventilation air side auxiliary heaters based on PTC elements is steadily increasing. In addition to ceramic PTC elements, electrical heating devices are increasingly being used on the basis of non-ceramic materials, such as those based on plastics. Electrical heaters made of PTC plastic elements have at least the advantage over ceramic PTC elements that they are much lighter and beyond that can be designed easily, such as in an injection molding process.

In order to achieve a good to very good electrical connection, for example to an electrical contact plate, in particular in a generic PTC plastic element, it is advantageous if at least those surface regions of the PTC plastic element to which an electrical contact is to be made, with a additional contact layer is provided, by means of which, for example, a contact resistance between the PTC plastic element and the electrical contact plate can be reduced. Thus, a PTC element of an electric heater can be operated more energy efficient, which can be advantageous especially in motor vehicles with limited battery capacity.

It is an object of the present invention to further develop generic electric heaters with electric heaters based on a PTC element.

The object of the invention is an electrical device for heating, in particular a motor vehicle, with an electric heating device, with an electrical contact device and with a contact layer which is arranged in a contact region between the electric heater and the electrical contact device, wherein the electric heater is characterized in that means for compensating for mechanical stresses in the contact region of the electric heater and the electrical Contact device are arranged.

Advantageously, the means for compensating for mechanical stresses, hereinafter also referred to as compensating means, in the contact area, reduce the risk that mutually electrically connected components of the electric heating device lose their mutual contact properties owing to constant temperature changes, thereby leading to a critical deterioration of the electrical contact can come between the electrical contact device and in particular the contact layer of the electric heater. In the worst case, for example, the contact layer of the electric heater can be solved.

It is understood that the electric heater is exposed to very high temperature fluctuations. Thus, the temperature range of use of the present electric heater may be in the range of -40 ° C to 80 ° C without the electric heater itself being activated. When the electrical heating device is activated, the operating temperatures can easily reach 120 ° C. This can cause temperature differences of up to 160 ° C. For example, this can be done when the electric heater is turned on at -40 ° C outside temperature, but still no ventilation air for cooling the electric heater is passed through the electric heater through. Due to different coefficients of thermal expansion of the individual components of the electric heating device, critical stresses can quickly occur at the contact points or joints of the components For example, it may come to the above-mentioned separation phenomena on the contact layer.

Advantageously, such critical mechanical stresses between individual, in particular glued together, components of the electric heating device can be particularly well prevented by means of the present compensating means. So even the existing adhesive joints, the risk is reduced that solves the adhesive bond between two components or worst case tears, which could also lead to dangerous micro-arcs.

For these reasons, a particularly good fatigue strength of all components of the electric heater is ensured, especially in bonded contact areas.

The term "electrical device for heating", in short electrical heating device, in particular heating devices are detected, by means of which a passenger compartment of a motor vehicle can be heated exclusively or additionally. Such electrical heaters are used successfully especially when a regular heating device of a motor vehicle can not be heated sufficiently well by a coolant circuit of an internal combustion engine of the motor vehicle. In such a case, the present electric heater can advantageously heat a ventilation air supplied to the passenger compartment, so that the passenger compartment can already be heated shortly after the start of the internal combustion engine, for example. In this context, the electric heater is often used only as zuheizvorrichtung on a motor vehicle and can therefore also be referred to as an electric heater.

By means of the term "electric heater" are described in the sense of the present invention, any devices that can heat when passing through electricity such that they can heat a ventilation air for heating a passenger compartment. Preferably, the electric heater is designed here as a PTC thermistor component of the electric heater.

In the present case, an "electrical contact device" means any device by means of which electricity can be supplied to an electrical heating device.

The term "contact layer" in this context refers to any structures by means of which an electrical contact between an electrical heating device and an electrical contact device can be designed particularly well. Such a contact layer is expressly advantageous in electrical heating devices made of plastic, since the contact layer can reduce a contact resistance to the plastic, whereby a particularly high power density can be achieved. By means of a suitable contact layer, substantially more adhesives can also be used on the electrical heating device. This is partly due to the fact that in connection with a plastic body as an electric heater only special adhesives can be used.

Preferably, the contact layer comprises tin, silver and / or gold. Thus, a metal layer is preferably used with respect to the contact layer, which has a particularly good electrical conductivity, as it can be used in conventional electrical connectors.

With the "contact area" are ideally all contact points between an electrical contact device and an electrical heating device, in particular a contact layer provided there, detected, the one Allow passage of electricity from about the electrical contact device to the electric heater.

It is understood that the compensating means according to the invention can be of various shapes, for example by mechanical spring elements in the contact region between the electrical heating device and the electrical contact device in order to be able to compensate for critical mechanical stresses which, for example, can not be compensated for by the components concerned alone.

The compensating means can be provided in a structurally particularly simple and very effective manner if the compensating means provide at least one further layer of material in the contact region of the electrical heating device and of the electrical contact device. As a result, the compensating means in the form of a further material layer could ideally be realized directly with the application of the above-described contact layer to the electric heating device.

For example, the electric heater is made of a plastic. Made of plastic electrical heaters are almost unlimited in their design and with known manufacturing processes, such as by injection molding, very inexpensive to produce. This makes it easily possible to make the entire electric heater so compact that they not only centrally in a motor vehicle heating, for example in an air conditioner of a motor vehicle, but also decentralized, for example, in or before discharge openings of the vehicle heating, can be attached. Preferably, a plastic body forms the electric heating device such that the plastic body is the only heat-generating electric heating device. If the plastic body, as explained in the description of the figure, also shaped as a plastic rib body, it can essentially also form the only heat-emitting surface of the electric heater. A particularly compact and easy-to-build design of the electric heating device can be realized if, in particular, the electrical contact device is bonded to the contact layer of the electric heating device. In turn, the electrical contactor can conduct electricity particularly well when made of an aluminum or alloy thereof or a copper alloy. It is indisputable that an electrical contact device, such as a copper alloy, an electric heater made of a plastic body and an adhesive for connecting the two components of the electric heater at a temperature increase can vary greatly and at different rates. This can cause damage to the heater, which can significantly interfere with the electrical contact between the components.

With the at least one further material layer critical stresses due to such different dimensions, in particular at bonded contact points of a contact area, can be advantageously compensated, so that the risk is reduced that the individual components tear apart in the contact area.

Due to the fact that even a single additional layer of material in addition to the conventional contact layer can significantly reduce the above-described risks in the contact area, a two-layer contact coating of the contact layer and the other applied to the electric heater material layer in the contact area already without the other features of the invention advantageous.

The at least one further material layer can have a variety of functional properties. In particular, in the present case, any material layers can be used that in the sense of the explained compensating means compensate for critical stresses in the contact area. A preferred embodiment in this context provides in this case that the compensation means are formed by a bonding agent, which is arranged between the contact layer and the electric heater.

Advantageously, the connection between a plastic body and a contact layer can thus be significantly enhanced if, in addition, a bonding agent is used by means of which the contact between the plastic body and the contact layer can be considerably intensified. In this way, in particular the risk can be reduced that the contact layer of the plastic body dissolves even with strong temperature fluctuations.

Preferably, the primer may comprise chromium. The adhesion promoter can hereby be applied as a thin adhesive layer to the plastic body of an electrical heating device, wherein the adhesive layer preferably consists of chromium, since on the one hand chromium is very reactive and on the other hand it can increase the adhesive strength of the contact layer. In particular, in the case of plastic bodies made of polyethylene (PE), it is advantageous if the PVD process is used in vacuum for coating the plastic body. In this way, a particularly intimate connection between the bonding agent and the electric heater can be ensured from a plastic body.

In practical tests it has also been found that it is advantageous if the adhesion promoter has a bonding agent thickness between 5 nm and 500 nm, preferably between 20 nm and 150 nm. An adhesion promoter thickness between 20 nm and 150 nm already causes a significant reduction in the risk that the contact layer suffers due to critical stresses in a contact area a defect.

In order to achieve a particularly good adhesion of the adhesion promoter on a plastic body of the electric heater, the plastic body should be pre-cleaned, for example, with acetone, and ideally be subjected to a plasma cleaning in the vacuum chamber before a coating process. It makes sense for the layer structure to be carried out successively in a coating process. Optionally, even after the application of the adhesion promoter in the PVD process, the plastic body can be subjected to a galvanization, for example when a contact layer is applied.

Another highly advantageous embodiment provides that means for reducing tensile stress in the contact region of the electric heater and the electrical contact device, in particular on a heater side adhesion promoter, are provided.

Cumulatively or alternatively, means for reducing tensile stresses, short of reducing agents, can be seen in front of the electric heater. In particular, the contact layer in the contact region of an electrical heating device and an electrical contact device can have a very high tensile stress when the electrical heating device and the electrical contact device expand differently and / or rapidly due to temperature fluctuations.

By means of such reducing agents, the fatigue strength of all components of the electric heating device can be further improved.

Structurally particularly simple, the reducing agents are formed by an intermediate layer, which is arranged between the contact layer and a bonding agent.

In such a variant, a three-layer contact coating is created in the contact region, by means of which advantageously a critical stress of the contact layer present there can be avoided particularly well.

It is also advantageous if the intermediate layer comprises copper. In particular, the intermediate layer can distribute forces occurring within the contact coating very well, which in particular can reduce the tensile stress between the bonding agent and the electric heater or a plastic body of the electric heater. Ideally, the material copper is used as an intermediate layer, a relatively soft material.

It is understood that the intermediate layer can be formed almost arbitrarily strong. However, it has been found that the intermediate layer can have a particularly good effect on an adhesive bond if the intermediate layer has an intermediate layer thickness of between 0.5 μm and 15 μm, preferably between 1 μm and 5 μm.

If no adhesive connection is provided in a contact region, but the components of the electrical heating device are clamped together mechanically, the intermediate layer may optionally be dispensed with, so that the contact coating can only have the previously described two-layered layer structure.

A particularly intimate and reliable connection of the components of the electrical heating device in a contact region can already be created if the contact layer and the heating device side are arranged an adhesion promoter on the contact side and if an intermediate layer is arranged between the contact layer and the adhesion promoter.

A particularly preferred embodiment provides a contact coating with a layer structure of contact layer, intermediate layer and adhesion promoter. By means of a contact coating constructed in this way, means for compensating for mechanical stresses in the contact region between the electrical heating device and the electrical contact device of the electrical heating device, and in particular also means for reducing tensile stress in the contact region, can be realized in a particularly compact design.

Advantageously, the contact coating has a total layer thickness between 0.2 μm and 30 μm, preferably between 2 μm and 10 μm.

Such a designed overall layer thickness shows in particular a very good abrasion resistance and beyond a particularly good dielectric strength with respect to micro-arcs in the contact region of the electric heater. It is understood that the total layer thickness of the contact coating can be selected higher. However, this results in no significant advantages in terms of improved abrasion resistance or improved dielectric strength in micro-arcs in the contact area of the electric heater. In addition, higher total layer thicknesses lead to higher costs with no or only negligible low Mehmutzen.

The term "contact coating" in the sense of the present invention is characterized in that the contact coating comprises at least two layers of material. In this way, the contact coating differs from a conventionally used contact layer, which consists only of one material layer, albeit possibly in multiple layers. Decisive for a permanently good contact coating is also the choice of the materials used, the different material layers of the Contact coating advantageously designed to. Ideally, the present contact coating is constructed in three layers, so that it can compensate especially well for movement in particular between components of the electric heating device glued together. The present contact coating is preferably a metallization, in particular a plastic surface, in which all material layers of the contact coating have good electrically conductive properties.

Since the present contact coating with its unusual layer structure advantageously continues to form conventional electrical heating devices even without the other features of the invention, all the features explained in connection with the contact coating are extremely advantageous on their own or in combination with one another.

In connection with the present contact coating, the contact layer may also be referred to as the top or cover layer, to which, for example, an electrical contact device of the electrical heating device is glued. If the contact layer in this case has a contact layer thickness of between 0.5 μm and 15 μm, preferably between 1 μm and 5 μm, the contact layer is already sufficiently strong to be able to permanently ensure stable and good electrical contact.

As already explained, it is advantageous if the electrical heating device comprises a PTC thermistor whose electrical resistance increases with increasing temperature, so that the electrical heating device essentially provides a constant heating power.

The electric heater can be designed differently. If the electrical heating device, as already indicated above, has a plastic ribbed body, it can be made particularly compact be because the plastic rib body can be flowed through directly by a ventilation air, the ventilation air can heat very well.

Alternatively, the electric heating device may also have a plastic plate body, which does not flow through due to its plate body of a ventilation air to be heated but can only be flowed around. In order that heat energy to the ventilation air can be delivered in an improved manner, in particular with regard to such a plastic plate body, it is advantageous if the electric heating device has corrugated fins which can additionally be flowed through or flowed through by the ventilation air to be heated. As a result, the heat energy output of the electric heater to the ventilation air is significantly improved.

It is understood that such corrugated fins can be made versatile. A particularly compact construction obtains the electric heater, when the electrical contact means comprises a corrugated fin of the electric heater. As a result, it is structurally particularly easy that electricity can be supplied to the electric heating device by means of a corrugated fin attached to the electric heating device.

A particularly strong connection between the corrugated fin and the electrical heating device can be produced if the corrugated fin is arranged directly on the contact layer or on the contact coating of the electrical heating device.

The term "direct" here describes that the corrugated rib rests as an electrical contact device directly on the contact layer or on the contact coating of the electric heater, so that substantially no further structure between the corrugated fin and the contact layer or the contact coating is arranged. As a result, the electricity from the corrugated fin can be conducted directly into the contact layer or into the contact coating.

A preferred embodiment in this context provides that the corrugated fin is fixed to the contact layer or to the contact coating by means of an electrical insulator, in particular an electrically insulating adhesive. With regard to the direct contact between the corrugated fin and the contact layer or the contact coating, the electrically insulating adhesive is naturally not between the corrugated fin and the contact layer or the contact coating.

An alternative embodiment provides that the corrugated fin is arranged indirectly on the contact layer or on the contact coating of the electrical heating device.

The term "indirectly" here describes a connection between the corrugated rib as electrical contact device and the contact layer or the contact coating, in which between the corrugated fin and the contact layer or the contact coating another structure is arranged, so that an electrical contact substantially only over this further Structure between the corrugated fin and the contact layer or the contact coating can come about.

If the corrugated fin is fastened to the contact layer or to a contact coating by means of an electrically conductive adhesive, the corrugated fin can be attached to the contact layer or to the contact coating in a particularly simple manner. By means of the electrically conductive adhesive can also advantageously particularly large contact areas in the contact area between the electrical Contact device and the electric heater can be ensured.

Preferably, an adhesive used in connection with the present invention also has an at least elastic basic behavior even after curing, so that the adhesive used can also withstand different expansion work with regard to an electrical heating device, an electrical contact device and a contact coating.

As an alternative to the adhesive connections described above, the components of the electrical heating device, in particular the electrical contact device with the electric heater, can also be clamped together mechanically. As a result, can be dispensed with a corresponding adhesive, but instead of the adhesive correspondingly suitable clamping means must be used, by means of which the components of the electric heater can be permanently clamped together.

Further advantages, objects and characteristics of the present invention will be explained with reference to the following description of the appended drawing, in which by way of example alternatively designed electric heating devices and their components as well as suitable manufacturing methods are illustrated. Components which in the figures at least substantially coincide with respect to their function may in this case be identified by the same reference numerals, these components not having to be numbered and explained in all figures.

It shows

FIG. 1

1 is a schematic perspective view of an electric heating device with plastic ribbed bodies as electrical heating means;

FIG. 2

1 schematically a perspective view of a further electrical heating device with plastic plate bodies as electrical heating devices, with corrugated fins as a heat transfer network and with electrical contact devices,

FIG. 3

2 is a schematic view of an electric heater provided with a contact coating on both sides;

FIG. 4

1 is a schematic view of a three-layer layer structure of a contact coating on both sides of an electrical heating device;

FIG. 5

2 is a schematic view of a diagram with characteristics of a ceramic cold conductor and a plastic cold conductor,

FIG. 6

1 is a schematic view of a crystalline and an amorphous state of a plastic cold conductor,

FIG. 7

1 is a schematic perspective view of a single plastic rib body with contact webs with a three-layer contact coating;

FIG. 8

schematically a detailed view of a contact coating on the contact webs of the individual plastic rib body of the FIG. 7 .
FIG. 9 schematically shows a detailed view of a contact region of an electrical contact device and the single plastic rib body of the FIG. 7 .
FIGS. 10 to 13 schematically a possible process flow for producing a glued electric heating device according to FIG. 1 .
FIG. 14 1 is a schematic view of a plastic sheet body provided on both sides with a three-layer contact coating;
FIG. 15 schematically a detailed view of the plastic plate body from the FIG. 14 .
FIG. 16 schematically another detail view of the plastic plate body from the FIG. 14 or 15 with a corrugated fin arranged thereon,
FIG. 17 schematically a detailed view of a heating module of the electric heater of the FIG. 2 consisting of a plastic plate body with three-layer contact coatings arranged on both sides thereon, of two corrugated ribs and of two electrical contact plates,
FIG. 18 schematically shows a detailed view of an adhesive connection between the upper corrugated fin of the heating module from the FIG. 17 and the upper three-layer contact coating on the one hand and one of the two contact sheets on the other hand,
FIG. 19 schematically a view of another heating module of an electric heater with a plastic plate body with two-layer contact coatings applied on both sides, and with trapezoidal ribs,
FIG. 20 schematically a detailed view of an adhesive connection between the Trapezwellrippen from the FIG. 19 and the related plastic plate body,
FIG. 21 1 schematically shows a view of a further electrical heating device comprising a plastic plate body provided on both sides with three-layer contact coatings and corrugated fins attached thereto as a direct electrical contact device of the electrical heating device,
FIG. 22 1 is a schematic of a detailed view of an alternative adhesive bond between a plastic plate body coated on both sides with three-layer contact coatings and corrugated ribs, wherein the adhesive bond comprises an electrically conductive adhesive,
FIGS. 23 to 25 alternative application method of an adhesive of a direct adhesive bond from the FIG. 25 .
FIGS. 26 to 31 schematically a possible process flow for producing a glued electric heating device according to FIG. 2 .
FIG. 32 schematically a view of a stapled electrical heating device with plastic plate bodies as an electric heater and with it mechanically stretched corrugated fins and contact plates as electrical contact means, and
FIG. 33 schematically a perspective view of a stapled electric heating device with a plastic rib bodies as electrical heaters and a mechanically tensioned electrical contact sheet.

The in the FIG. 1 shown electric heater 1 is provided for installation in an air conditioner of a motor vehicle, not shown here. The electric heater 1 comprises a total of four electric heaters 2 (numbered here only by way of example), which are each formed as a plastic rib body 3. The plastic rib bodies 3 are produced by means of a plastic injection molding process. But they can also be extruded, sintered or made by another suitable method.

At their radial ends 4 and 5, which are arranged radially with respect to a longitudinal plane 6 of the electric heater 2, each of the electric heaters 2 is provided with a first electrical contact means 7 and a second electrical contact means 8, wherein each of the electrical contact means 7 and 8 a electrical connection 9 (numbered here only by way of example). In order to substantially improve the electrical contact between the electrical contact devices 7 or 8 and the respective heating device 2, in one of the respective contact regions 10 a contact coating 11 (described in more detail below) is provided (see in particular FIG FIG. 4 ) intended.

In particular, the electrical heating device 1 in the respective contact report 10 advantageously has means 12 for compensating for mechanical stresses (see in particular FIG FIG. 4 ), so that even electric heaters 2 and electrical contact means 7, 8 with strong Deviating expansion coefficients can be reliably and permanently connected to each other. As a result, the fatigue strength of the electric heater 1 is substantially increased.

By means of the plastic rib body 3, a ventilation air 13, by means of which a passenger compartment of the motor vehicle to be heated, are structurally particularly easy to be heated.

The electric heater 1 can advantageously be constructed modularly, if a plastic rib body 3 and one or two electrical contact means 7, 8 are glued together to form a heating module 14 and thus made available compact. For example, 2 to 8 such modules 14 are glued together. The individual heating modules 14 can in this case be controlled jointly or separately via the electrical connection.

With regard to the further electric heater 101 from the FIG. 2 the electric heaters 2 are not formed as a plastic rib body 3, but as a plastic plate body 15 (numbered here for clarity only exemplified).

The plastic plate body 15 is in each case equipped on both sides with a contact coating 11 (numbered here only by way of example). Since the plastic plate body 15 as an electric heater 2 per se has no rib contour over which heat energy of the electric heater 2 can be advantageously delivered to ventilation air 13, a corrugated fin 16 is attached to each of the electric heaters 2 and to their contact coatings 11, respectively the heat energy of the electric heaters 2 can be transmitted to the corrugated fins 16. The ventilation air 13 can flow through these corrugated fins 16, whereby the generated by the electric heaters 2 Heat energy then by means of corrugated fins 16 to the ventilation air 13 over a large area and therefore can be given advantageous. An exceptionally good thermal conductivity of the corrugated fins 16 can be ensured here if they are made of aluminum.

In this embodiment, the corrugated fins 16 are each glued to the contact coating 11 of the electric heaters 2, so that the corrugated fins 16 with the electric heater 2 and the respective contact coating 11 can be advantageous and structurally simple in contact.

The supply of electricity of the electric heaters 2 is ensured by means of electrical contact means 7 and 8, wherein the electricity from the contact means 7 and 8 via the corrugated fins 16 in the respective plastic plate body 15 can be initiated. The electrical connection of the electrical contact devices 7 and 8 can be made via an electrical connection 9. The electrical contact means 7 and 8 are also designed in this embodiment as a flat contact sheets.

With regard to the electric heating device 101, a heating module 14 preferably consists of a plastic plate body 15, two corrugated fins 16 and a first contact device 7 and a second contact device 8, wherein here, too, each of the heating modules 14 is individually controllable.

The electrical heaters 2 explained in the present case are cold conduction bodies which are made of plastic. As a result, the electric heating devices 1, 101 can be produced substantially more cost-effectively and, moreover, can be made more diverse, for example directly as a plastic ribbed body 3.

Is an electric heater 2 (see FIG. 3 ) provided on both sides by means of a contact coating 11, the electric heater 2, together with its two contact coatings 11, a total resistance 20 for an electric current flow 21. Here, a negative terminal 22 and a positive terminal 23 are shown schematically. The total resistance 20 results from a first surface resistance 24, a first contact resistance 25, a contact resistance 26, a second contact resistance 27 and a second surface resistance 28.

The surface resistances 24 and 28 depend essentially on the quality of the connection between the electrical contact device 7 or 8 and the contact coating 11.

The contact resistances 25 and 27 result essentially from the structure of the contact coating 11.

By contrast, the volume resistance 26 depends essentially on the material from which the electrical heating device 2 is made. Also, the selected thickness 29 of the electric heater 2 plays an essential role in the passage resistance 26.

Using the example of a further detailed illustration of an electrical heating device 2 in the form of a plastic plate body 15 provided on both sides with a contact coating 11, a preferred layer structure 31 of the contact coating 11 is shown.

The layer structure 31 consists in this embodiment of a first layer 32, a second layer 33 and a third layer 34. The first layer 32 forms a contact layer 35 of the contact coating 11, by means of which the electric heater 2 with an electrical contact means 7, 8 in Can contact. The second layer 33 forms in this embodiment, an intermediate layer 36, by means of which the contact layer 35 in the present case can be connected to the third layer 34 of the contact coating 11. In the present case, the third layer 34 is formed by a bonding agent 37, by means of which the contact coating 11 can enter into a particularly intimate connection with the electrical heating device 2.

In particular, the adhesion promoter 37 provides a further material layer 38 in a contact region 10 (see in particular FIG.) Between the electrical heating device 2 and one of the electrical contact devices 7 or 8, by means of which the means 12 for compensating mechanical stresses in the contact region 10 are advantageously created can.

In a very simple embodiment, which is not shown here, the adhesion promoter 37 in conjunction with the contact layer 35 can form a two-layer compensating means.

However, while the adhesion promoter 37 essentially forms the compensation means 12, the intermediate layer 36 provides means 39 for reducing tensile forces in a contact region 10 (see in particular FIG FIG. 1 ) of the electric heater 2 and the electrical contact device 7 and 8, in particular on a heater side adhesion promoter 37, is.

In a further exemplary embodiment not shown here, an advantageous contact coating could also be composed of only the contact layer 35 and the second layer 33 as a reducing means 39 of tensile stress forces within the contact coating 11.

The layer structure 31 after the FIG. 4 However, the Kontaktschicht 35 on the contact device side and on the heater side, the adhesion promoter 37, wherein between the contact layer 35 and the adhesion promoter 37 additionally an intermediate layer 36 is arranged.

In order to ensure a particularly good abrasion resistance and dielectric strength with respect to micro-arcs, the contact coating 11 of the layer structure 31 has a total layer thickness 40 of 8 μm.

The contact layer 35 used here consists of a silver alloy, so that a good contact between an electrical contact device 7 or 8 and the contact layer 35 can be ensured.

In this case, the compensating means 12 or the adhesion promoter 37 has chromium, since chromium is very reactive and can ensure good adhesion of the contact coating 11 to the electrical heating device 2. Tensile forces, in particular within the contact coating 11, can advantageously be reduced if the intermediate layer 36 is made of copper or a suitable copper alloy. In particular, copper is an excellent electrical conductor and a soft material that can easily compensate for tensile stresses.

By means of the layer structure 31 of the contact coating 11 described here, it is possible to effectively prevent the contact layer 35 from breaking off from the electric heating device 2 if such an equipped electric heating device 1 or 101 is exposed to strong temperature differences. As a result, the fatigue strength of the electric heater 1, 101 is particularly advantageous increased.

The contact coating 11 can in particular be applied to the heating device 2 advantageously by means of vapor deposition, for example a PVD coating in a plastic body made of PE, by means of at least partial electrodeposition and / or by means of an approximately self-adhesive metal foil.

That in the FIG. 5 45 shows a relationship of a PTC ceramic 46 with respect to a first PTC plastic 47 and another PTC plastic 48. In the diagram 45, in particular the relationship between the specific resistance R and the temperature T with respect to the PTC materials 46, 47 and 48, it being readily apparent that the respective RT gradient, which can describe a measure of a Ableitverhalten a PTC thermistor, the PTC plastics 47 and 48 at least as steep as that of the PTC ceramic 46, whereby the PTC Plastics 47 and 48 are also particularly well for electrical heaters 2 can be used.

Depending on the composition of the PTC plastic 47, 48, the respective relevant R-T characteristic can be set in a selectable adjustment range 49. In particular, this results in different application areas 50 and 51, which are shown in gray in the diagram 45.

The different plastic compositions can be created, for example, by providing a polyolefin with different amounts of soot. The proportions of carbon in this case provide carbon components in the respective plastic 47, 48, which are arranged in the plastic 47, 48 (see FIG FIG. 6 ). At an average ambient temperature or a corresponding room temperature, a plastic body 52 essentially has a crystalline structure 53 in which the carbon components may be formed as electrically conductive carbon chains 54. As a result, the plastic body 52 is low impedance.

Considering the same plastic body 52 at a higher temperature results in a substantially amorphous structure 55, in which the electrically conductive carbon chains 54 are divided into individually distributed carbon chain pieces 56, so that the plastic body 52 is high impedance.

In other words, the plastic body 52 is a PTC thermistor whose electrical conductivity decreases with increasing temperature 57. As soon as the temperature drops again 58, the electrical conductivity of the plastic body 52 can be taken again, since the carbon particles can reassemble into electrically conductive carbon chains 54.

The in the FIGS. 7 to 9 shown plastic rib body 3 is provided at its two radial ends 4 and 5 each with a plurality of contact webs 60. The plastic ribbed body 3 can be traversed by a ventilation air 13, wherein it can heat the ventilation air 13, if it is heated itself.

An electrical contact device 8 can be glued to the contact webs 60 (see detailed view of FIG FIG. 9 ). In order to be able to produce an adhesive bond 61 with a particularly high fatigue strength between the contact webs 60 and the contact device 8, the contact webs 60 are coated with the contact coating 11 described above (see in particular FIG FIG. 8 ).

If electricity 62 is now introduced into the electrical contact device 8, a current flow 21 (here shown only by way of example on one of four vertical arrows) flows through the plastic rib body 3, as a result of which can warm up. Preferably, the current flow 21 is in this case aligned in the direction of the contact webs 60, so that the longest possible current flow 21 through the plastic rib body 3 and thus a particularly good heating of the plastic rib body 3 can be achieved.

Advantageously, the surface resistance 24, 28 and the contact resistances 25 and 27 (see FIG. 3 ) are substantially reduced by means of the contact coating 11, whereby, inter alia, a higher flexibility of the electrical connection of an electric heater 2 can be achieved. In addition, the electric current density in the contact region 10 can be advantageously reduced. Further, the contact coating 11 forms a seal of the plastic surface on the contact webs 60, so that a particularly good contact between an electrical contact device 7 or 8 and an electric heater 2 can be ensured even in the long term.

In the FIGS. 10 to 13 is a possible process sequence for producing a heating module 14 from a plastic rib body 3 and a first electrical contact device 7 and a second electrical contact device 8 with a glued structure (see FIG. 13 ).

At first ( FIG. 10 ), the plastic ribbed body 3 is present as plastic granules 63, wherein the plastic granules 63 are formed into the actual plastic ribbed body 3 ( FIG. 11 ). In this case, after the plastic granules 63 have been heated, the plastic granulate 63 can either be injection molded, extruded, sintered or produced with another advantageous plastic production method.

After the plastic ribbed body 3 is produced as a heating device, the plastic ribbed body 3 is cleaned at least at its radial ends 4 and 5, so that there contact webs provided 60 are particularly well freed from impurities. Optionally, before coating with an electrically insulating adhesive 64 (see FIG. 12 ) a plasma treatment of the plastic rib body 3.

If the electrically insulating adhesive 64 is applied on both sides of the plastic rib body 3, the electrical heating devices 7 and 8 are supplied and pressed against the contact webs 60 of the plastic rib body 3 by suitable pressure rollers 65 (numbered here only by way of example). Here, the contact pressure of the pressure rollers 65 is advantageously selected so high that the electrically insulating adhesive 64 can be at least partially displaced at the contact webs 60, whereby the contact webs 60 rests directly on the electrical contact means 7 and 8 respectively. As a result, a direct electrical contact between the plastic rib body 3 and the electrical contact means 7 or 8 is provided, so that in the present case the electrically insulating adhesive 64 can be used. The adhesive 64 may in this case be brushed or sprayed onto the corresponding components, or the components of the heating module 14 to be glued together may be immersed in an adhesive reservoir. Curing of the electrically insulating adhesive 64 can take place by means of an increase in temperature, for example in an oven, by means of hot air, by means of UV light or simply at room temperature.

In this embodiment, the plastic rib body 15 may have a thickness of between 5 mm and 100 mm, which may depend substantially on its later use.

In addition to the above-described plastic rib body 3 as an electric heater 2, the electric heater 2 may alternatively be used as a plastic plate body 15, as in the electric heater 101 from the FIG. 2 already shown, be designed (see FIG. 14 ).

This plastic plate body 15 is provided on both sides with a contact coating 11, which preferably has a layer structure 31 (see FIG. 15 ), which consists of a contact layer 35, an intermediate layer 36 and a bonding agent 37, as described in detail with reference to the further detail representation 30 from the FIG. 4 has already been explained. Here, the plastic plate body 15 may have a preferred thickness between 0.4 mm and 5 mm. The thinner the plastic plate body 15 is selected, the better its heat extraction can be. The thicker the plastic plate body 15 is selected, the more stable the entire structure. A good compromise was found when the plastic sheet body thickness is chosen between 0.7 mm and 2 mm.

Advantageously, the contact coating 11, in addition to the advantages explained above, also has a positive influence on an electrical connection to electrically conductive particles, such as carbon particles (see FIG. 6 ), in the plastic ribbed body 3.

Since the plastic plate body 15 per se has no rib shape through which a ventilation air 13 can be passed therethrough, in each case a corrugated fin 16 is glued to the plastic plate body 15 or in particular to the contact coatings 11, wherein the corrugated fin 16 is equipped with an electrical contact means 7 (see FIG. 16 ). The electrical contact device 7 may in this case have a contact plate thickness between 0.3 mm and 2 mm, wherein a contact plate thickness between 0.5 mm and 1 mm represents a very good compromise in terms of good stability and good weight.

A rib of the corrugated fin 16 preferably has a rib thickness of 0.05 mm to 0.2 mm. If the corrugated fin 16 additionally designed as a current-carrying component, the rib thickness is preferably 0.08 mm to 0.15 mm. A rib height can be between 3 mm and 20 mm or between 5 mm and 20 mm. The rib depth can be 4 mm to 50 mm or 6 mm to 20 mm. The dimensions mentioned here also depend on the heat output of the electric heater.

A related heating module 14, with a preferred depth between 5 mm and 100 mm, from a plastic plate body 15, two corrugated fins 16 (only exemplified here) and a first electrical contact device 7 and a second electrical contact device 8 is in the FIGS. 17 and 18 shown.

The corrugated fins 16 serve to increase a heat-transferring surface of the heating module 14, so that a heat generated by the heater 2 can be transmitted much better to a ventilation air 13 flowing through the corrugated fins 16. Advantageously, the contact coating 11 also improves the thermal conductivity between the electrical heating device 2 and the corrugated fins 16, so that in particular a very homogeneous heat distribution over the entire length of the corrugated fins 16 can be established.

In this exemplary embodiment, the first electrical contact device 7 is poled as a positive pole 23 and the second electrical contact device 8 as a negative pole 22, so that in particular a flow of current 21 can flow through the plastic plate body 15, wherein the current flow 21, as explicitly in the FIG. 18 indicated, is also directed by the electrical guide 7 and the corrugated fin 16 of the positive pole 23 to the negative terminal 22.

In particular, according to the illustration of FIG. 18 one recognizes adhesive bonds 61 between the corrugated fin 16 and the plastic plate body 15 on the one hand and the electrical contact means 7 on the other. Here, the corrugated fin 16 is in direct contact with the plastic plate body 15 or to the electrical contact device 7, since the electrically insulating adhesive 64 is provided only in the meniscus areas 66 of the corrugated fin 16.

While a previously explained corrugated fin 16 was formed only V-shaped, is in the FIGS. 19 and 20 an arrangement 67 of a plastic plate body 15 and two Trapezwellrippen 68 (numbered here only by way of example) shown. It is advantageous that the trapezoidal rib 68 in the contact region 10 can rest on the contact coating 11 of the plastic plate body 15 in a substantially larger area, so that excellent electrical contact between the trapezoidal ribs 68 and the plastic plate body 15 can thereby be ensured.

The trapezoidal ribs 68 are formed by means of an adhesive bond 61 with an electrically insulating adhesive 64, wherein the electrically insulating adhesive 64 is arranged only in meniscus regions 66 of the adhesive bond 61. This can be ensured by pressing the trapezoidal shafts 68 against the plastic plate body 15 so strongly in the manufacturing process of the arrangement 67 that the electrically insulating adhesive 64 is displaced from the immediate contact region 10. A contact force must be selected to be correspondingly high, so that the electrically insulating adhesive 64 can also be displaced by the larger contact surface.

In the further embodiment 69 of the FIG. 21 are the corrugated fins 16 which are adhered to a plastic plate body 15, each formed directly as a first electrical contact means 7 and as a second electrical contact means 8. Such a constructed heating module 14 constructively constructs particularly simple, since a positive pole 23 and a negative pole 22 is formed directly from the respective rib 16. Preferably, at least one of the corrugated fins 16 is a connecting element 70 is provided, on which two corrugated fins 16 can be attached directly opposite lying. Here, the connecting element 70 does not serve as an electricity-initiating device but merely as an assembly and stop help. An electric heater 101 equipped with such heating modules 14 is particularly easy to construct, since additional electrical contact means can be dispensed with.

The in the FIG. 22 shown further adhesive connection 71 is realized with an electrically conductive adhesive 72, wherein the electrically conductive adhesive 72 between corrugated fins 16 and contact coatings 11 of a plastic plate body 15 is enriched. As a result, the corrugated fins 16 are not directly on the contact coatings 11, but only indirectly, since there is between the corrugated fins 16 and the contact coatings 11 even when cured adhesive bond 71, the electrically conductive adhesive 72. By means of the electrically conductive adhesive 72, a direct contact between the corrugated fins 16 and the contact coatings 11 is not required, so that even with a relevant manufacturing process is not necessarily to ensure that the adhesive 72 is completely displaced between the corrugated fins 16 and the contact coatings 11 , As electrically conductive adhesive 72 here is a silicone adhesive has been used.

The electrically insulating adhesive 64 or the electrically conductive adhesive 72 can be applied as an adhesive strip 73 on a contact coating 11 of a plastic sheet body 15 (see FIG. 23 ). Or the adhesives 64 and 72 are applied to the corrugated fin 16 (see FIG. 24 ), wherein then the plastic plate body 15 and / or the electrical contact means 7 are brought in accordance with the direction arrows 74 and 75 to the corrugated fin 16 and pressed together.

In both cases, the corrugated fin 16 (see FIG. 25 ) are brought into direct contact with the plastic plate body 15 and the electrical guide 7, respectively.

A possible process sequence for producing an electric heating device 101 according to FIG FIG. 2 is in the FIGS. 26 to 31 shown schematically. Here, a plastic granules 63 is heated and formed into a plastic semi-finished plate 76 (see FIG. 27 ). On this plastic semi-finished plate 76 are on both sides of a contact coating 11, ideally according to the further detailed representation 30 of the FIG. 4 , applied. Subsequently, the thus-prepared plastic semi-finished plate 76 is cut into individual plastic plate body 15. Advantageously, the plastic plate body 15 are provided on both sides directly with the required contact coatings 11.

Following this, an electrically conductive adhesive 72 is applied to the respective contact coating 11 and solidified by means of suitable pressure rollers 65. Corrugated ribs 16 can be glued to the thus prepared plastic plate body 15, whereby individual heating modules 14 can be produced, which in turn can be glued together in an appropriate manner to an electric heater or otherwise clamped together.

As an alternative to the glued electrical heating devices 1 or 101 explained above, it is also possible to implement structural variants 77 and 78 with respect to electrical heating devices 1, 101 with electrical heating devices 2 made from a plastic plate body 15 or from a plastic ribbed body 3.

In the related construction variant 77 from the FIG. 32 are two heating modules 14 with plastic plate bodies 15, with corrugated fins 16 and with electrical contact means 7 and 8 inserted in a frame 79, wherein the two heating modules 14 are braced by suitable clamping means 80 within the frame 79 with each other. This ensures a required pressure for a good electrical contact and a good heat extraction between the individual components. Due to the tension springs 80, which ensure a certain component extent 81 when heated within the frame 79, a particularly high requirement for compensating means 12 or reducing means 39 in the form of a contact coating 11 (see FIG. 4 ) not mandatory.

In the further construction variant 78 from the FIG. 33 an electrical contact means 7 is clamped by means of tension springs 80 to connecting webs 60 of a plastic rib body 3, so that even with respect to a related contact coating 11 lower claims can be made.

With the exemplary embodiments explained here, an electrical heating device 1, 101 with electrical heating devices 2 made of plastic can be made substantially less expensive, lighter and more versatile than with conventional PTC ceramic elements. In particular with the contact coating 11 described here, critical stresses and / or forces within the electrical heating device 2 can be substantially reduced. Also, the contact coating 11 is more resistant to micro-arcs than conventional simple contact coatings. This can be attributed, in particular, to the special layer structure 31, which consists of at least three different material layers 32, 33 and 34. In this way, the present contact coating 11 differs in particular from conventional contact layers, which have only a single material layer. Even if a conventional contact layer should be multi-layered, it has the advantageous layer structure 31 not on, the present invention, the contact coating 11 is characterized.

References list

1

electric heater

2

electric heating device

3

Plastic ribs body

4

first radial end

5

second radial end

6

longitudinal plane

7

first electrical contact device

8th

second electrical contact device

9

electrical connection

10

contact area

11

Contact plating

12

Means for compensating mechanical stresses

13

ventilation air

14

heating module

15

Plastic disk body

16

corrugated fin

20

total resistance

21

electric current flow

22

minuspol

23

positive pole

24

first surface resistance

25

first contact resistance

26

Contact resistance

27

second contact resistance

28

second surface resistance

29

Thickness of the electric heater

30

further detailed presentation

31

layer structure

32

first shift

33

second layer

34

third layer

35

contact layer

36

interlayer

37

bonding agent

38

additional material layer

39

Means for reducing tensile forces

40

Total layer thickness

45

diagram

46

PTC ceramic

47

first PTC plastic

48

second PTC plastic

49

Adjustment

50

a first area of application

51

a second area of application

52

Plastic body

53

crystalline structure

54

electrically conductive carbon chains

55

amorphous construction

56

individually distributed carbon chain pieces

57

rising temperature

58

sinking temperature

60

contact bars

61

adhesive bond

62

electricity

63

Plastic pellets

64

electrically insulating adhesive

65

pressure rollers

66

meniscus areas

67

arrangement

68

Trapezoidal corrugated fin

69

another embodiment

70

connecting element

71

further adhesive connection

72

electrically conductive adhesive

73

adhesive strips

74

first directional arrow

75

second directional arrow

76

Plastics semi-plate

77

Design variant

78

further construction variant

79

frame

80

tension springs

81

component expansion

101

another electric heater

Claims (15)

Electric device (1, 101) for heating, in particular a motor vehicle, with an electrical heating device (2), with an electrical contact device (7, 8) and with a contact layer (35), which in a contact region (10) between the electric heater (2) and the electrical contact device (7, 8), characterized by means (12) for compensating for mechanical stresses in the contact region (10) of the electrical heating device (2) and the electrical contact device (7, 8). Electric heating device (1, 101) according to claim 1, characterized in that the compensating means (12) provide at least one further material layer (38) in the contact region (10) of the electric heating device (2) and the electrical contact device (7, 8) , Electric heating device (1, 101) according to claim 1 or 2, characterized in that the compensating means (12) are essentially formed by a bonding agent (37) which is arranged between the contact layer (35) and the electric heating device (2). Electric heating device (1, 101) according to claim 3, characterized in that the adhesion promoter (37) comprises chromium. Electric heating device (1, 101) according to claim 3 or 4, characterized in that the adhesion promoter (37) has a bonding agent thickness between 5 nm and 500 nm, preferably between 20 nm and 150 nm. Electric heating device (1, 101) according to one of the preceding claims, characterized by means (39) for reducing tensile stresses in the contact region (10) of the electrical heating device (2) and the electrical contact device (7, 8), in particular on a heater side adhesion promoter (37). Electric heating device (1, 101) according to claim 6, characterized in that the reducing means (39) of an intermediate layer (36) are formed, which between the contact layer (35) and a bonding agent (37) is arranged. Electric heating device (1, 101) according to claim 7, characterized in that the intermediate layer (36) comprises copper. Electric heating device (1, 101) according to claim 7 or 8, characterized in that the intermediate layer (36) has an intermediate layer thickness between 0.5 .mu.m and 15 .mu.m, preferably between 1 .mu.m and 5 .mu.m. Electric heating device (1, 101) according to one of the preceding claims, characterized in that the contacting device side (35) and the heater side, a bonding agent (37) are arranged, and that between the contact layer (35) and the adhesion promoter (37) an intermediate layer ( 36) is arranged. Electric heating device (1, 101) according to one of the preceding claims, characterized by a contact coating (11) with a layer structure (31) comprising a contact layer (35), an intermediate layer (36) and a bonding agent (37). Electric heating device (1, 101) according to claim 11, characterized in that the contact coating (11) has a total layer thickness (40) between 0.2 μm and 30 μm, preferably between 2 μm and 10 μm. Electric heating device (1, 101) according to one of the preceding claims, characterized in that the electrical contact device (7, 8) comprises a corrugated fin (16) of the electric heating device (1, 101). Electric heating device (1, 101) according to claim 13, characterized in that the corrugated fin (16) is arranged indirectly on the contact layer (35) or on a contact coating (11) of the electrical heating device (2). Electric heating device (1, 101) according to claim 13 or 14, characterized in that the corrugated fin (16) on the contact layer (35) or on a contact coating (11) by means of an electrically conductive adhesive (72) is attached.

Images