EP1921896B1 - Heat producing element for electrical heating device and its method of manufacturing - Google Patents

Description

The present invention relates to a heat-generating element having at least one PTC heating element, on both sides thereof sheet-applied conductor tracks and a frame which forms at least one frame opening for receiving the at least one PTC heating element.

Such a heat-generating element is as part of a Zuheizers for a motor vehicle, for example from the EP 0 350 528 known. Other heat-generating elements are for example from the DE 32 08 802 . DE 30 46 995 or DE 28 04 749 known.

In principle, the problem with such generic heat-generating elements is that a good contact resistance is to be provided by good mechanical contacting between the conductor track and the PTC element, so that energization of the heat-generating element without substantial heating at the phase boundary to the PTC element is possible , This requirement becomes particularly relevant when the heat-generating element is to be energized with high operating voltages of about 500 volts or more.

In generic electric heaters, the conductor track, which is usually formed by an electrically conductive sheet metal, encapsulated by a surrounding the heat-generating element sleeve which applies the conductor with a certain pressure against the at least one PTC element (see above DE 32 08 802 ). In this prior art, the PTC element is surrounded with the mutually adjacent tracks with a metallic sleeve, which is coated on the inside with silicone rubber, so that the conductive metal sheets are held in the insulating sleeve. This arrangement alone is not sufficient to build up a sufficient contact pressure for pressing the strip conductors against the PTC element. Accordingly, the entire layer structure is surrounded by a press plate. Thus, the previously known heat-generating element is relatively sluggish, ie heat generated by the PTC element is relatively poorly dissipated to the outside. The As a result, the previously known heat-generating element has a poor thermal efficiency and reacts relatively slowly to changing thermal conditions.

For heat dissipation it is for example from the EP 0 350 528 It is known to apply radiator elements formed on both sides of the heat-generating element by means of meandering bent metal sheets. These are applied under spring bias against the heat-generating element. Since the interconnect between the radiator element and the at least one PTC element is provided so as to be freely movable, the interconnect is applied against the PTC element via the spring force. In this construction, however, there is the problem that leakage currents that migrate, in particular, during operation of the heat-generating element with high voltages across the radiator element and / or the frame can not be avoided. In addition, the current-carrying parts are exposed on the outside of the heat-generating element, which is also questionable for reasons of safety.

The aforementioned disadvantage with respect to a poor heat conduction has also from the DE 28 04 749 known heating element, in which three generic heat-generating elements are arranged at an angle of 120 ° about a cylinder axis. Between the individual heat-generating elements are cylindrical circular segment pieces of an electrical insulating material, in each of which a flow channel for a to be heated by the heating cartridge fluid are recessed. Such a structure is insufficient particularly in the convective removal of heat generated by the PTC element by air. Heat can not be dissipated to the required extent by the PTC element.

The present invention is based on the problem of specifying a heat-generating element, in which a good contact between the conductor track and the at least one PTC element can be ensured. The present invention is also intended to specify an electric heater which preferably comprises the heat-generating element according to the invention, in which the heat-generating elements are accurately positioned. The present invention is also intended to specify a method for producing a corresponding electrical heating device.

To solve the problem with respect to the heat-generating element, the present invention proposes a heat-generating element with at least one PTC element, on both sides flat adjacent thereto strip conductors and a frame which forms at least one frame opening for receiving the at least one PTC element surrounding it in that the frame is formed as part of a housing, which forms a structural unit with at least one of the conductor tracks and a wedge element, wherein the wedge element has a first wedge surface extending parallel to the conductor track and one exposed on the outside of the housing, includes obliquely aligned to the first wedge surface second wedge surface.

With the present invention, a heat-generating element is proposed, the housing forms a structural unit together with a wedge element. The housing comprises the frame, which circumferentially surrounds the at least one PTC heating element, so that the housing allows for a positionally accurate positioning of the at least one PTC heating element in the heat-generating element. In addition, the housing holds the wedge member as part of a structural unit, which means that the wedge member is fixed in some way within the housing. This does not exclude that the housing has an opening through which the wedge element can be removed. Nevertheless, the movement of the wedge element in different directions of movement is only possible within certain limits. The wedge element is used to clamp the heat-generating element between two heat dissipating through the line surfaces, such as surfaces of radiator elements, which are flown by air to be heated. Due to the housing, the heat-generating element can be first brought with the wedge element received therein in a mounting position in which the wedge element has to clamp the heat-generating element between two heat-emitting surfaces. Here, the housing may comprise a further housing part, which has, for example, a conductor track, which rest on the wedge element facing away from the back of the PTC or these elements. The further housing element is preferably provided as part of the structural unit, ie opposite the housing part having the wedge element at least only within predetermined limits movable.

In a preferred embodiment, the structural unit comprises the at least one PTC heating element and the two conductor tracks. As already mentioned, the housing may consist of at least two housing parts which are movable relative to one another and which are not necessarily connected to one another in the context of the structural unit. Thus, the frame opening may be partially formed by walls of a housing part and partially by walls of another housing part. For assembly reasons alone, it is expedient to provide a frame opening on a housing part, which can receive the PTC heating elements or components sufficiently securely within the frame during assembly. Moreover, within the housing or individual housing parts, the conductor track or tracks can be movable, in particular in one direction towards and away from the at least one PTC heating element, as freely as possible over the wedge element in the layer structure comprising at least one external contact force To initiate PTC heating element and the adjacent conductor tracks. However, to reduce the number of parts and with a view to simple assembly, it will be preferable to arrange only one printed conductor within limits within the housing and to arrange the other printed conductor fixed relative to the housing.

The various parts of the layer structure, that is, the two strip conductors lying flatly against the at least one PTC element, and the PTC elements preferably arranged next to one another in a plane are preferably held by the wedge element. This is either already in the preassembled state, ie recorded in the housing, or biased only after final assembly of the heat-generating element in a heater relative to the at least one PTC element. In any case, however, the wedge element is preferably arranged so that it holds the aforementioned elements of the layer structure within the housing. The one wedge surface of the wedge element extends parallel to the conductor track and can abut this directly or with the interposition of an insulating layer, so that the layer structure consisting of the two conductor tracks and the at least one PTC element is securely biased, whereby a good electrical contact ensured between the two interconnects and the at least one interposed PTC heating element becomes. The second wedge surface of the wedge element, which is arranged obliquely to the first wedge surface, is exposed on the outside of the housing. Thereafter, the second wedge surface is suitable for direct contact with a heat-emitting element, for example, to a radiator element, which is formed by a meandering bent sheet metal strip. Alternatively, a partition wall of an electric heating device may abut directly on the second wedge surface, which is traversed on its other side by a fluid to be heated, for example air or water.

For bracing the layer structure in the housing and / or for installation of the heat-generating element to surrounding walls within an electric heater, it is preferable to form the housing with a guide in which the wedge member is slidably mounted. The guide is preferably designed so that when inserting the wedge element, the second wedge surface is increasingly pressed against a counter surface, which may for example also be formed by the housing, so that the wedge the voltage applied to the other side conductor against the at least one PTC element presses. It can be provided on both sides of the PTC element wedge elements. Usually, however, sufficient for biasing the mutual conductor tracks against the at least one PTC element, a wedge element on one side of at least one PTC heating element and on the opposite side a stationary fixation of the conductor against the PTC heating element, which preferably integrally formed on the housing will, off.

With a view to easy manufacture of the heat-generating element, it is preferable for the guide to be formed to extend substantially parallel to the longitudinal side of the PTC heating element and to be provided with an opening through which the wedge element can be pushed into the housing from the outside. This makes it possible, for example, first insert a conductor in the housing, then the one or more PTC elements and then on the other side of the first conductor a second conductor. Only after the layer structure has been introduced into the housing, the wedge element can be inserted from the outside into the housing, whereby the layer structure is joined together with the wedge element to form a preassembled structural unit. As a structural unit of the present invention, a unit is understood in which the wedge member is still loosely attached to the housing and / or removably disposed in the housing.

The guide of the wedge element in the housing may preferably be effected by guide grooves, which are recessed on the housing and in which guide webs which are formed laterally on the wedge element, d. H. at those end faces which connect the first wedge surface with the second wedge surface.

According to a further preferred embodiment of the present invention, the housing is designed to taper in the insertion direction of the wedge element. The wedge element and the housing are preferably matched to one another such that in a holding position in which the wedge element secures the aforementioned layer structure from falling out of the housing, the wedge element pushed into the housing does not project beyond its second wedge surface of this housing. In other words, the wedge element in the holding position can secure the parts of the layer structure in the housing against falling out. However, the outside of the housing on the side of the inserted wedge element is not formed by the wedge element, but by the housing surface, so that in the holding position, the heat-generating element according to the invention can be positioned accurately, for example, in an electric heater. For in the holding position the outer sides provided in the extension of the side surfaces, ie the outer surfaces of the heat-generating element extending parallel to the conductor tracks are first formed by the housing whose dimensions can be predetermined with the usual manufacturing tolerances. In a relation to the holding position in the insertion direction deeper clamping position of the wedge element, however, one of the outer sides of the heat-generating element is formed by the second wedge surface, which projects beyond the housing. With this preferred embodiment, it is possible to first introduce the heat-generating element with predetermined dimensions, for example in a pocket or recess of an electric heater and then by deeper insertion of the wedge element in the clamping position, the wedge element and thus the entire heat-generating element against the heat dissipating walls of an electric heater create and bias against them. In this case, the layer structure is braced against each other, ie the tracks are applied under bias against the interposed PTC heating element and this is braced against the inner walls of the bag.

It has proven to be expedient to dimension the wedge element so that it extends in the holding position in the insertion direction of the wedge element over at least two thirds of the length of the associated conductor track. The conductor track is usually formed from a sheet-metal strip, so that even in the case where several PTC heating elements are provided in a plane next to each other, the sheet metal strip together with the wedge element already sufficiently fixed in the housing, the layer structure in the holding position, d. H. secures against falling out.

With regard to a good conduction of the heat generated by the PTC element to the outside, it is further preferable to dimension the wedge element such that it covers in the clamping position the at least one provided in the housing PTC heating element substantially over the entire surface. This ensures that the heat generated by the PTC element is conductively discharged to the outside through the wedge element and discharged therefrom, for example, by a radiator element directly adjacent to the wedge element, so that the heat generating element has a low thermal inertia and a high thermal efficiency ,

In particular, for applications with high voltages, it is preferable to provide an insulating layer applied to the conductor track between the wedge element and the adjacent conductor track. This can be formed for example by a plastic strip or a ceramic layer. Preferably, in the arrangement of a ceramic layer adjacent to the conductor track should also be provided between the ceramic layer and the wedge element a sliding plate, which is preferably held stationary in the housing and on which the wedge element slides when inserted into the housing. As a result, a solid friction between the wedge element and the relatively rough and brittle ceramic layer is avoided. This development also prevents that for pressing the wedge element into the housing, for example, in the final assembly of the heat-generating element in a heating device, required pressing force is significantly affected by the friction conditions, as is to be feared in an immediate past sliding of wedge element and ceramic insulating layer.

Incidentally, the aforementioned sliding plate can be provided according to a further preferred embodiment of the present invention for compensating for manufacturing tolerances in the layer direction of the layer structure formed by the conductor tracks and the at least one provided therebetween PTC heating element with different thickness. The need for such a compensation of manufacturing tolerances is conceivable, for example, if a plurality of heat-generating elements, which are formed by identically dimensioned PTC elements, conductors and wedge elements and housing to be inserted next to one another in a pocket, which is subject to certain manufacturing tolerances. Incidentally, the ceramic PTC heating elements of a batch have production-related tolerances that can be compensated by a metal sheet with adapted strength. Thus, it is conceivable to classify PTC elements of a batch in terms of their strength and to arrange PTC elements of the same thickness in a housing, which compensate for differences in thickness caused by the selection of different thickness PTC heating elements for different heat-generating elements.

While the wedge element bears directly or with the interposition of a further layer, for example an insulating layer on the one side of the PTC element adjacent conductor, preferably provided on the opposite side of the conductor track preferably be connected together with an adjacent insulating layer by encapsulation with the housing. This creates the possibility of simply inserting the PTC elements in the one-sided already closed housing, which is then closed on the other side after placing the conductor on the outside of the PTC heating elements with the wedge element.

The above-mentioned, preferably formed by a ceramic plate insulating layer is used according to a preferred embodiment of the present invention to sealably receive the conductor in the frame. For this purpose, the insulating layer is sealingly against the housing, for example via a provided between the insulating layer and the housing seal, which may be formed for example by an adhesive strip which fixes the insulating layer to the housing. This prevents moisture from getting to the layer structure accommodated in the housing, which promotes leakage currents. Insofar as below to the insulating or sealing recording of Conductor is turned off within the housing, this is done in particular with regard to a preferred embodiment, in which the conductor track is formed by an elongated conductor element, such as an elongated metal strip. Between opposite sheet metal strips several PTC heating elements are arranged side by side in a plane. It comes in this preferred embodiment in particular on the circumferential sealing or insulating receiving the at least one PTC element relative to the insulating layer. The PTC heating elements can be fixed, for example, with respect to the insulating layer and be provided at a distance from the walls of the frame openings, so that leakage currents can not flow through the frame. In the same way, the frame opening can be lined on the inside with a highly insulating material, for example a silicone, in order to avoid a direct contacting of the electrically conductive elements of the layer structure with the electrically inferior material of the frame. The frame is here preferably made as an injection molded part of a relatively inexpensive, not highly insulating plastic, such as polyamide.

For further manufacturing simplification and in view of a predetermined energy density when installing a plurality of heat-generating elements in a pocket of an electric heater is proposed to provide an leading to the guide insertion opening for the wedge element at an upper end side of the housing. On the upper side leading to the printed conductors leading contact tongues are also provided, which pass through the housing recessed contact tongue openings. The upper end side then serves the electrical connection of the heat-generating element as well as the insertion of the wedge element. The upper end face of the housing is usually free on the upper side when the heat-generating element is installed in a pocket of an electrical heating device, so that the individual heat-generating element can be electrically connected to this upper side.

The aforementioned bag usually has a multiple length of the heat-generating element. With regard to optimum utilization and heating of the bag over its entire length, it is preferably proposed that the housing forms spacer elements with spacer surfaces extending transversely to the contact tongues on this upper end face. These spacer surfaces extend in the longitudinal direction of the contact tongues and are upstream or downstream of the at least one PTC element in the longitudinal direction.

The spacer surfaces are arranged corresponding to one another so that adjacent heat-generating elements inserted in one and the same pocket abut one another in a predetermined manner with their front and rear spacer surfaces, so as to reliably set the desired spacing of adjacent heat-generating elements.

With regard to a positionally accurate positioning of the heat-generating element in the pocket is proposed according to a further preferred embodiment of the present invention that the housing at its upper end on either side of the at least one PTC element each one transverse to the contact tongues and in the thickness direction of the at least forming a PTC element extending stop. About this stop the maximum penetration depth of the heat generating element is set in the bag. This penetration depth is reached when the stop abuts against the upper edge of the bag.

The abovementioned spacer surfaces and the stops are preferably formed as part of a circumferential ring, which preferably ends flush with the top of the housing and surrounds the housing on the upper side.

For production-related simplification of the heat-generating element, the housing comprises a housing shell element and a housing shell counter element, which may also be formed as a shell. In this regard, too, the circumferential envelopment of the at least one PTC element in the case of an elongate layer structure with a plurality of PTC elements arranged one behind the other between sheet-metal strips is of particular importance. The two housing elements are connected by means of encapsulation with a conductor track or optionally with an insulating layer surrounding this on the outside. The insulating layer or the conductor track are then inserted as an insert into an injection mold for producing the housing shell elements. One of the housing elements, d. H. either the housing shell or the housing shell counter element, forms the guide for the wedge element.

The housing elements are also substantially immovable to each other by engagement in the insertion direction of the wedge element. This can be done on the opposite Surfaces of the housing elements corresponding projections or recesses, for example, pins may be provided with pin holes. However, these are dimensioned so that a relative movement of the two housing elements in a direction substantially perpendicular to the insertion direction is possible. When pressing the layer structure in a pocket so that the housing elements are moved relative to each other with their respective tracks, possibly the insulating layers fixed therein until the tracks are sufficiently firmly pressed on both sides against the or the PTC element (s). This requires that the two housing elements are dimensioned so that a certain gap remains between the denser outer surfaces of the housing elements before the dense contact of the printed conductors on the PTC elements.

With regard to a complete isolation of the electrically conductive parts of the layer structure, it is proposed according to a preferred development of the present invention that a compressible, the frame opening sealing sealing means is provided between the two housing elements. This is dimensioned such that in conceivable relative movements for applying the conductor tracks against the PTC element by the compressible sealing means, a seal of the recessed from the housing elements, the layer structure receiving interior is achieved. The compressible sealant may be formed by a rubber. It is also conceivable to provide the sealing means with certain adhesive properties, so that the housing elements are glued together by the sealing means in the prefabricated state.

In particular, in the aforementioned preferred embodiment of the heat-generating element, the housing elements are produced as separate components by means of injection molding and joined after inserting the at least one PTC element in the frame. As a joined unit within the meaning of the invention, the collapse of the housing elements is already understood, without it being necessary that they are firmly or captively connected to each other. Joining may, for example, be understood as the telescoping of interlocking elements, which fix the two housing elements in the direction of insertion of the wedge element substantially immovably to each other. The housing elements joined in this way can, for example, be held fixed in a heating device after being inserted into a pocket. In this application, it is not necessary to fix the housing elements against each other. Of course it is not excluded to fix the two housing elements, for example by welding on pins which are formed on one of the housing elements and the other of the housing elements protrude and exposed on the outside of the housing element. By welding or spreading by melting of such pins, the two housing elements can be captive, but held sufficiently movable to each other.

With regard to a simple assembly of the heat-generating element is proposed according to a further preferred embodiment of the present invention, on one of the housing elements, which comprises the guide for the wedge element, a frame opening for receiving the at least one PTC element surrounding housing projection, which is has substantially in the insertion direction extending projection edges. Corresponding thereto, a housing recess is formed on the other housing element, which accommodates the housing projection. The housing recess and the housing projection are formed corresponding to one another, such that the housing projection fits straight into the housing recess. As a result, the two housing elements are fixed transversely to the insertion direction against each other. To facilitate joining the edges should be slightly conical, so that the housing recess having housing element initially arranged relatively inaccurate with respect to the housing projection and can be supplied to this and advancing supply movement, the two housing elements by the oblique edge surfaces are increasingly fixed against each other. The projection edges should be designed to be higher in the feed direction than other form-fitting elements, such as fastening pins on a housing element, which engage in pin recesses on the other housing element, so that initially a relatively coarse positioning of the two housing elements can be done by housing recess and housing projection and only in a later phase the feeding movement by uniaxial displacement of the pins with the corresponding recesses for covering and must be brought into engagement.

Figur 1

eine perspektivische Seitenansicht eines ersten teilweise montierten Ausführungsbeispiels eines wärmeerzeugenden Elementes vor dessen Fertigstellung;

Figur 2

eine Ansicht gemäß Figur 1 für einen weiteren, nachgeordneten Fertigungsschritt;

Figur 3

eine Ansicht gemäß den Figuren 2 und 3 nach fertiger Montage des Ausführungsbeispiels des wärmeerzeugenden Elementes;

Figur 4

eine Querschnittsansicht des in Figur 3 gezeigten Ausführungsbeispiels;

Figur 5

eine perspektivische Seitenansicht eines zweiten Ausführungsbeispiels eines wärmeerzeugenden Elementes;

Figur 6

eine perspektivische Draufsicht auf ein erstes Gehäuseelement des in Figur 5 gezeigten Ausführungsbeispiels;

Figur 7

eine perspektivische Draufsicht auf ein zweites Gehäuseelement des in Figur 5 gezeigten Ausführungsbeispiels, welches komplementär zu dem in Figur 6 gezeigten Element ausgebildet ist;

Figur 8

eine perspektivische Draufsicht der beiden in den Figuren 6 und 7 gezeigten Gehäuseelemente vor dem Fügen derselben;

Figur 9

eine perspektivische Schrägansicht eines Ausführungsbeispiels einer elektrischen Heizvorrichtung, die unter Verwendung mehrerer wärmeerzeugender Elemente gemäß dem Ausführungsbeispiel in Figur 5 erstellt worden ist;

Figur 10

die in Figur 9 gezeigte perspektivische Darstellung mit teilweise weggenommenem Heizergehäuse;

Figur 11

eine Querschnittsansicht durch das in Figur 9 gezeigte Ausführungsbeispiel und

Figur 12

eine teilweise geschnittene Seitenansicht des in Figur 9 gezeigten Ausführungsbeispiels.

Further details and advantages of the present invention will become apparent from the following description of embodiments in conjunction with the drawings. In this show:

FIG. 1

a side perspective view of a first partially assembled embodiment of a heat-generating element before its completion;

FIG. 2

a view according to FIG. 1 for a further, subordinate production step;

FIG. 3

a view according to the Figures 2 and 3 after the finished assembly of the embodiment of the heat-generating element;

FIG. 4

a cross-sectional view of in FIG. 3 shown embodiment;

FIG. 5

a side perspective view of a second embodiment of a heat generating element;

FIG. 6

a perspective top view of a first housing element of in FIG. 5 shown embodiment;

FIG. 7

a perspective top view of a second housing element of the in FIG. 5 shown embodiment, which is complementary to the in FIG. 6 formed element is formed;

FIG. 8

a top perspective view of the two in the FIGS. 6 and 7 shown housing elements before joining them;

FIG. 9

an oblique perspective view of an embodiment of an electric heating device, which uses a plurality of heat-generating elements according to the embodiment in FIG. 5 has been created;

FIG. 10

in the FIG. 9 shown perspective view with partially taken away heater housing;

FIG. 11

a cross-sectional view through the in FIG. 9 shown embodiment and

FIG. 12

a partially sectioned side view of the in FIG. 9 shown embodiment.

In the in the FIGS. 1 to 5 the embodiment shown is a heat-generating element 1 with a one-piece housing 2, which in an end view (see FIG. 4 ) is wedge-shaped tapering downwards. The housing 2 forms a frame 4, which encloses a frame opening 6, in the present four PTC heating elements 8 can be accommodated, of which in FIG. 3 only three PTC Heizelemenet 8 are shown. The four superimposed in a plane PTC heating elements 8 are spaced from the wall of the frame 4 by pins 10, which are formed of a highly insulating material, for example, a bonded by encapsulation with the plastic of the housing 2 silicone, which better The pins may also be integrally connected to the housing 2 by injection molding in their base and coated with a highly insulating sleeve of ceramic or a highly insulating plastic.

The PTC heating elements 8 rest on a conductor track, which in the exemplary embodiment shown is formed by a sheet metal web 12 which is uniformly connected to the housing 2 by means of encapsulation. The metal sheet 12 has a substantially rectangular cross section and is cut at its upper end to form a contact tongue 14 by punching. The contact tongue 14 extends through a contact tongue opening 16, which surrounds the contact tongue 14 circumferentially and is formed during encapsulation of the sheet metal strip 12 by the plastic material surrounding the contact tongue 14.

At the protruding from the contact tongue 14 upper end face 18 of the housing 2, a further contact tongue opening 20 is recessed, which opens to the side surface of the housing 2 out and to which will be discussed in more detail below. To the upper end face 18 of the housing 2 also opens a guide 22 with guide grooves 24 for a later described in detail wedge element, which in FIG. 1 not shown. A lateral guide surface of the guide grooves 24 is formed by the surface of the frame 4. The opposite guide surface of the guide grooves 24 is formed by a guide web 26 which projects beyond this first guide surface and is formed by the housing 2. The guide web 26 extends substantially over the entire height of the housing, ie from the upper end face 18 to a lower end face 28. At the lower end face 28 is an opposing cheeks 30 of the housing 2 connecting end wall 32, which the guide grooves 24th complete on the underside. Like the sectional view in FIG. 4 illustrates a frame opening 6, the lower side bounding bottom wall 34 of the frame 4 is higher than the end wall 32. This lower wall 34 may be upstream of highly insulating pins that prevent direct contacting of the lower PTC heating element 8 with the lower wall 34.

Between the lower wall 34 and the lower end of the housing 2, the frame 4 forms a contact surface 36 for a in FIG. 1 not shown sheet metal web. On the opposite side, the metal sheet 12 can be overlapped by an encapsulation and thus secured to the housing 2.

Like the sectional view in FIG. 4 can be seen, the outside of the sheet metal web 12 is a ceramic plate 38 as an insulating layer, which is also connected by encapsulation with the housing 2.

The frame 4 and connected to the housing 2 elements sheet metal web 12 and ceramic plate 38 thus form with the frame opening 6 a one-sided closed receptacle for the PTC heating elements 8. In this recording, the PTC heating elements can be easily inserted and fixed there first stationary.

In another, in FIG. 2 indicated manufacturing step is then applied to the sheet metal web 12 opposite side of the PTC heating elements 8, a further metal sheet 40, which is provided with a contact tongue 42. The contact tongue is in this case inserted from the outside into the further contact tongue opening 20. This further metal sheet 40 is surrounded on the outside by a ceramic plate 44, which rests flat against the other metal sheet 40 and this projects beyond the outside. The ceramic plate can be sealed relative to the housing 2, in particular via a highly insulating, the further metal sheet 40 surrounding sealing strip made of a highly insulating plastic, preferably with adhesive properties, which rests against the frame opening 6 surrounding surface of the frame 4. This prevents that creepage currents are introduced via the further metal sheet 40 in the plastic of the housing 2. For the same reasons, the other sheet metal strip 12 may be dimensioned so that it covers only the PTC elements 8, the holder of the sheet metal web 12 and the ceramic plate 38, however, takes place solely on the encapsulation of the ceramic plate 38. The electrically conductive parts of the heat-generating element, ie, the two metal sheets 12, 40 and the PTC heating elements 8 are then supported in any case highly insulating within the frame opening. A leakage between the two metal sheets 12, 40 on the plastic material of the frame 4 must not be feared thereafter. The heat-generating element is therefore particularly suitable for Operating at high voltages, for example in a voltage range of between 100 volts and 400 volts.

As part of the further assembly, a sliding plate 46 is then externally applied against the ceramic plate 44, the dimensions of which corresponds approximately to the dimensions of the ceramic plate 44 and which covers the ceramic plate 44 on the outside and supports.

After the further sheet metal web 40, the ceramic plate 44 and the sliding plate 46 have been inserted from the side against the frame 4 and into the housing 2, from the upper end face 18, a wedge member 48 in the housing 2 by a recessed on this insertion 49th inserted. The wedge element has a first wedge surface 50, which is in this case externally placed against the sliding plate 46, and a second wedge surface 52, which is formed obliquely to the first wedge surface 50, with an inclination which is substantially the conical configuration of the housing 2 in Insertion direction of the wedge element 48 corresponds. The two wedge surfaces 50, 52 connecting end faces of the wedge element are surmounted by guide webs 54 which are formed on the wedge member 48 and fit into the guide grooves 24.

In the embodiment shown, the guide grooves 24 extend parallel to the recorded in the housing layer structure comprising the PTC elements 8, the both sides thereof adjacent sheet metal tracks 12, 40 and in this case the ceramic plates 38, 44 and the sliding plate 46. When inserting the wedge member 48 along the Guide 2 in the direction of the lower end face 28, in any case, in the illustrated embodiment, the individual layers of the layer structure are not placed against each other with pressure. Such an arrangement is nevertheless conceivable. Care should be taken here, however, that at a possible inclination of the guide grooves 26 relative to the layer structure or due to the wedge-shaped configuration of the wedge member 48 this as fully as possible and over the entire height of the layer structure is applied to this, so that the superimposed PTC elements 8 are each pressed with the most uniform contact force against the outside adjacent thereto tracks 12, 40.

In the FIGS. 4 and 5 is the wedge member 48 shown in its so-called holding position, in which the wedge member 48 secures the layer structure in the housing 2 against falling out, but with its second wedge surface 52, the housing 2 is not overtopped on the outside. In other words, in the holding position by the wedge member 48, the preassembled heat generating element is taken to a unity. The individual components can not fall apart or get lost. The wedge element 48 extends in its holding position over a little more than three quarters of the length of the associated conductor track 40, which is held fixed in position and keeps the PTC elements 8 stacked one above the other in the direction of insertion. In this holding position, the wedge element 48 does not protrude beyond the housing 2, but is clamped in the housing 2 in a stationary manner, for example due to the frictional forces between the guide grooves 24 and the guide webs 54.

The thus preassembled heat generating element 1 thus has a substantially predetermined by the housing 2 outer contour, which is surmounted only by the contact tongues 14, 42. A rear, the cheeks 30 bounding outer side surface 56 of the housing 2 therefore also forms the outer contour of the heat-generating element 1 on the wedge-element-side outer surface.

In the region of the upper end face 18, the housing 2 forms a circumferential rim 58, which protrudes outwards relative to the contour of the housing 2 in the area of the PTC heating elements 8 and the PTC elements 8 in the longitudinal direction upstream or downstream distance surfaces 60, 62 forms, which are formed corresponding to each other, in this case as a flat frontal spacing surfaces. In the transverse direction, d. H. Thickness direction of the PTC elements, this circumferential ring forms the housing-side side surface 56 and the ceramic plate 38 on the outside superior attacks 64, whose function will be explained in more detail below. The stops 64 extend transversely to the contact tongues 14, 42, d. H. transverse to the recorded in the housing 2 layer structure.

The FIGS. 5 to 8 show a further embodiment of a heat-generating element. Identical components are identified with the same reference numerals with respect to the previously discussed embodiment.

The main difference between the embodiment of FIGS. 1 to 4 and the embodiment now discussed is that the housing 2 is formed in the embodiment discussed here as a two-part housing with a housing shell 66 and a corresponding thereto shell-shaped housing counter-element 68. Both of these housing elements 66 and 68 are formed by injection molding and take by encapsulation in each case the ceramic plate 38, 44 and the sheet metal web 12, 40 in itself. This in FIG. 6 Housing shell element shown also forms the guide 22 for the wedge member 48, but which is formed as the guide of the first embodiment.

This in FIG. 6 shown housing shell member 66 has a frame opening 6 surrounding the housing projection 70, which projects beyond a substantially flat edge-side contact surface 72 of the housing shell member 66. The housing projection 70 is delimited by insertion edges extending in the insertion 74, which are slightly conically formed aufaufaufend.

This in FIG. 7 shown housing counter-element 68 has a corresponding to the housing projection 70 formed housing recess 76. Their outside abutment surface 80 has pin recesses 82 which correspond with pins 84 of the housing shell element 66, which project beyond the abutment surface 72 or the top side of the housing projection 70.

In the in the FIGS. 5 to 8 In the embodiment shown, the respective ceramic plates 38, 44 are fastened together with the metal sheets 12, 40 by means of encapsulation to the housing elements 66, 68 and received uniformly in them. By encapsulation is further carried out an external sealing of the frame 4, which in joined housing elements (cf. FIG. 8 ) is formed predominantly by the housing shell element 66 and to a small extent by the housing counter element 68.

Between the housing shell member 66 and the housing counter-element 68, a sealing strip, not shown in the drawing can be provided. This can, for example, the housing opening 6 surrounding between the housing projection 70 and the corresponding Counter surface of the housing shell counter element 68 may be provided. The compressibility of the sealing element is chosen so that even with certain manufacturing tolerances with respect to the thickness of the PTC heating elements 8 a secure sealing of the frame opening 6 is achieved. The required relative mobility of the two housing elements transversely to the layer of layer structure is performed by engagement of pin 84 and pin recesses 82. The pins 84 can latchingly engage in the pin recesses 82, so that the housing elements 66, 68 are held captive but relatively movable to each other. However, the housing elements 66, 68 equipped with the PTC heating elements 8 are already joined in the sense of the invention to form a unitary component when the pins engage one another and thus prevent a free movability of the housing elements 66, 68 against each other.

The FIGS. 9 to 11 show an embodiment of an electric heater with a heater housing 100 with a housing base 102 and a housing cover 104. The housing base 102 has a circulation chamber 106 which is connected via connections, of which only one terminal 108 is shown, with a line for fluid to be heated , The circulation chamber 106 is penetrated by a plurality of extending in the longitudinal direction of the housing base 102 pockets 110, which have a substantially U-shaped cross-sectional shape in the cross-sectional view and are circumferentially closed relative to the circulation chamber 106. These pockets 110 have a depth that is greater than the extension of the aforementioned heat-emitting elements in the insertion direction of the wedge member 48. The illustrated embodiment of an electric heater has four side-by-side pockets extending substantially the entire length of the housing base 102. The housing base 102 is formed as a diecast aluminum.

When removed housing cover 104 a plurality of heat-generating elements 1 are introduced into the individual pockets 110 each side by side, and indeed so far until the stops 64 abut against the edge of the pocket 110 on the upper side. The lateral distance of adjacent heat-generating elements 1 is maintained by abutting the corresponding spacing surfaces 60, 62. After positioning a single heat-generating element 1 in the pocket 110, the wedge member is further advanced from the retainer position in the insertion direction. This pushes the second wedge surface 52 after outside over the side surface 56 of the housing 2 and is brought into abutment with the aluminum wall of the bag. When inserting the wedge element 48 with a predetermined insertion force pressing of the heat-generating element 1 is achieved in the pocket, so that on the one hand the wedge element in good heat conduction between the inside of the bag and the top layer of the layer structure and on the other hand present on the other side outer layer of Layer structure rests directly against the other outside of the bag. During this final assembly of the heating element, the movement of the wedge element 48 is guided via the guide 22. Depending on the manufacturing tolerances, in particular the varying thickness of the PTC elements, the wedge element 48 can be pushed into the housing 2 at different depths. However, the housing 2 remains relative to the pocket 110 in its predetermined by the stops 64 and the spacing surfaces 60, 62 position. In the in the FIGS. 1 to 4 shown embodiment, thickness tolerances of the PTC elements can also be compensated by differently thick sliding plates 46. In the other embodiment of a heat generating element according to the FIGS. 5 to 8 The thickness compensation takes place by relative movement of the housing elements 66, 68 guided by the engagement of pin 84 and pin recesses 82nd

The heat-generating elements 1 are first applied with their distance surface 60 flush against a formed on the heater housing 100 stop when inserted into the corresponding pockets 110. As a result, the position of the respective first heat-generating elements 1 within the pocket 110 is predetermined. By conditioning the respective spacing surface 60, 62, the position of the next heat-generating element 1 in the longitudinal direction of the respective pocket 110 is also predetermined. Due to the stops 64, the penetration depth of the heat-generating elements 1 into the respective pocket 110 is also defined. The heat-generating elements 1 thus accommodated in a predetermined position in the housing base 102 can be electrically contacted in a simple manner by placing a printed circuit board with plug connections for the respective contact tongues 14, 42. For the sake of clarity was on the representation of such a board in the Figures 9 and 10 waived. But you have to imagine such a board as a component above the upper end face 18, but below the ends of the contact tongue 14 and 42, respectively. The contact tongues 14, 42 project through the board and are electrically connected to the board soldered and contacted the heat generating element 1 facing side of the board arranged Kontaktzungenaufnahmen.

LIST OF REFERENCE NUMBERS

1

heat generating element

2

casing

4

frame

6

frame opening

8th

PTC heating element

10

pencils

12

strip plate

14

contact tongue

16

Contact stud opening

18

upper end side

20

further contact tongue opening

22

guide

24

guide

26

guide web

28

lower front side

30

cheek

32

bulkhead

34

bottom wall

36

contact surface

38

ceramic plate

40

another sheet metal train

42

more contact tongue

44

ceramic plate

46

sliding

48

key member

49

insertion opening

50

first wedge surface

52

second wedge surface

54

guide web

56

outer side surface

58

wreath

60

space area

62

space area

64

attack

66

Housing shell element

68

Housing counter element

70

housing projection

72

contact surface

74

projecting lip

76

housing recess

80

contact surface

82

pin recess

84

spigot

100

heater housing

102

housing base

104

housing cover

106

circulation chamber

108

connection

110

bag

Claims (20)

1. Heat-generating element (1) with at least one PTC heating element (8), strip conductors (12, 40) lying flat on it on both sides and a frame (4) which forms at least one frame opening (6) for holding the at least one PTC heating element (8) and which surrounds this PTC heating element (8),
   characterised in that
   the frame (4) is formed as a part of a housing (2), which housing (2) forms a structural unit with at least one of the strip conductors as well as with a wedge element, wherein the wedge element (48) comprises a first wedge surface (50) that extends parallel to the strip conductor (12, 40) and a second wedge surface (52), aligned diagonally to the first wedge surface (50) and exposed on the exterior side of the housing (2).
2. Heat-generating element according to Claim 1, characterised in that the housing (6) comprises the at least one PTC heating element (8) as well as the two strip conductors (12, 40).
3. Heat-generating element according to Claim 1 or 2, characterised in that the housing (2) comprises a guide (22) in which the wedge element (48) is held in such a way that it can be slid.
4. Heat-generating element according to one of the preceding claims, characterised in that the guide (22) extends essentially parallel to a long side of the PTC heating element (8) and opens outwards so that the wedge element (48) can be inserted into the housing (2) from the exterior.
5. Heat-generating element according to Claim 4, characterised in that the wedge element (48) has guide ridges (54) on the side that are guided in guide grooves (24) cut into the housing (2).
6. Heat-generating element according to one of the preceding claims, characterised in that the housing (2) is formed so that it is tapered in the direction in which the wedge element (48) is inserted and that the wedge element (48) and the housing (2) are coordinated with each other in such a way that in a holding position, in which the wedge element (48) secures at least one PTC heating element (8) against falling out of the housing (2), the wedge element (48) inserted into the housing (2) does not protrude beyond the housing (2) with its second wedge surface (52) and that in a clamping position that lies deeper in the insertion direction than the holding position, the wedge element (48) protrudes beyond the housing (2) with its second wedge surface (52).
7. Heat-generating element according to one of the preceding claims, characterised in that in the holding position, the wedge element (48) extends in the insertion direction of the wedge element (48) over at least three-quarters of the length of the assigned strip conductor (40).
8. Heat-generating element according to one of the Claims 5 to 7, characterised in that in the holding position, the wedge element (48) does not protrude beyond the housing (2) at its rear face side (56) in the insertion direction.
9. Heat-generating element according to one of the preceding claims, characterised in that an insulating layer (44), positioned on the strip conductor (40), is provided between the wedge element (48) and the strip conductor (40) adjacent to this.
10. Heat-generating element according to one of the preceding claims, characterised in that a plate (46) is provided between the wedge element (48) and the at least one PTC heating element (8), wherein said plate (46) can be provided with various thicknesses for compensation of manufacturing tolerances in the direction of the layer composition formed by the wedge element (48), the strip conductors (12, 40) and the at least one PTC heating element (8).
11. Heat-generating element according to Claim 9 or 10, characterised in that the plate (46) is arranged between the wedge element (48) and the insulating layer (44).
12. Heat-generating element according to one of the preceding claims, characterised in that the strip conductor (12) provided on the side opposite the wedge element (48), together with an insulating layer (38) lying thereupon, is connected to the housing (2) by means of extrusion.
13. Heat-generating element according to one of the preceding claims, characterised in that the at least one strip conductor (40) is secured to the housing (2) by an insulating layer (44) that lies on the housing (2) forming a seal.
14. Heat-generating element according to one of the preceding claims, characterised in that the insulating layer (44) lying on the plate (46) is sealed with respect to the housing (2) by a sealing strip that surrounds the frame opening (6).
15. Heat-generating element according to one of the preceding claims, characterised in that the housing (2), on its upper face side (18), has an insertion opening (49) that leads to the guide (22) for the wedge element (48) and contact stud openings (16, 20) penetrated by contact studs (14, 42) leading to the strip conductors (12, 40) and that the housing (2), on its upper face side (18), forms spacing elements (58) that extend at right angles to the contact studs (14, 42), wherein said spacing elements (58) are formed corresponding to spacing surfaces upstream or downstream of the PTC heating element (8) and extending in the direction of the length of the contact studs (14, 42).
16. Heat-generating element according to one of the preceding claims, characterised in that the housing (2), on its upper face side (18), on both sides of the at least one PTC heating element (8), forms at least one limit stop (64) that extends to the contact studs (14, 42) and that extends in the thickness direction of the at least one PTC heating element (8).
17. Heat-generating element according to one of the preceding claims, characterised in that the housing (2) comprises a housing shell element (66) and a housing counter-element (69), each of which is connected to a strip conductor (12, 40) by means of extrusion and, where appropriate, to an insulating layer (38, 44) provided on the exterior, wherein one of these forms the guide (22) for the wedge element (48), and in that the housing elements (66, 68) are joined into a structural unit in such a way that they do not move with respect to one another by means of being meshed in the insertion direction of the wedge element (48), but in such a way that they are still movable with respect to one another in a direction essentially at a right angle to this.
18. Heat-generating element according to Claim 17, characterised in that a compressible sealing material that seals the frame opening (6) is provided between the two housing elements (66, 68).
19. Heat-generating element according to Claim 17 or 18, characterised in that the housing elements (66, 68) are manufactured as separate components using injection moulding and then connected to one another after insertion of the at least one PTC heating element (8) into the frame (4).
20. Heat-generating element according to one of the preceding claims, characterised in that the housing element (66) comprising the guide (22) for the wedge element (48) forms a housing projection (70) that surrounds the frame opening (6) and that has projection edges (74) that extend essentially in the insertion direction and in that the other housing element (68) forms a housing recess (76) that holds the housing projection (70).

Images