EP2846344B1 - Temperature-dependent switch - Google Patents

Description

The present invention relates to a temperature-dependent switch with a temperature-dependent switching mechanism, a housing receiving the switching mechanism, two provided on the switch first terminals, between which the switching mechanism in dependence on its temperature establishes or opens an electrically conductive connection, and with a heating resistor, the outside disposed on the housing and is electrically in series with the first two terminals.

Such a switch is from the DE 43 36 564 C2 known.

The well-known switch is designed as a sealed switch with two-piece, current-carrying metal housing, as he also for example from the DE 21 21 802 A or the DE 196 23 570 C2 is known. The encapsulated switch is arranged on a ceramic support plate, on which a thick-film resistor is arranged between conductor tracks, which at its one end is electrically connected to the conductive lower part the encapsulated switch is connected. The other end of this heating resistor is connected to one of the conductor tracks, which serves as a soldering surface, to which a first pigtail is soldered. The second pigtail is electrically soldered to the conductive lid portion of the sealed switch.

The lower part of the switch rests with its outer bottom on the heating resistor. The thick-film resistor can be covered by an insulating layer. The switch is to be soldered to a lateral trace on the Trägerplatter, which is not mentioned in this document, as the soldering is to take place. As a result, a linear cohesive contact is produced between the lower part and the conductor track serving as the soldering surface.

This connection is not only problematic to manufacture, but also mechanically not sufficiently stable, which is why the document shows that together on the switch and carrier plate, a shrink tube is shrunk, protrude from the side of the two connecting wires. As a result, the switch and carrier plate are additionally mechanically fixed to one another.

Such temperature-dependent switches are used in a known manner to protect electrical equipment from overheating. For this purpose, the switch is electrically connected via its two first terminals in series with the device to be protected and mechanically arranged on the device so that it is in thermal communication with this.

In the housing is in the embodiment of a switch according to the DE 196 23 570 C2 a temperature-dependent switching mechanism of spring washer, bimetallic snap-action disc and movable contact member is arranged, which is in the closed state of the switch in contact with a stationary contact part inside of the upper part, which is plated through to the outside to a first terminal on the upper part. Another first connection is the conductive lower part.

The operating current of the device to be protected flows through the two contact parts and the spring washer in the lower part.

The from the DE 43 36 564 C2 known switch is equipped because of the heating resistor with a current-dependent switching function, for which the heating resistor is permanently connected electrically in series with the first terminals. The operating current of the device to be protected thus constantly flows through this heating resistor, which can be dimensioned so that it ensures that the bimetallic snap disk is heated to a temperature above its response temperature when a certain operating current is exceeded, so that the switch at an increased Operating current already opens before the device to be protected has warmed up inadmissible.

Below the response temperature of the bimetallic snap disk, the circuit is closed and the device to be protected is powered by the switch with power. Increases the temperature either due to an excessive operating current or as a result of overheated, to be protected device beyond a permissible value, so deforms the bimetallic snap disk, whereby the switch is opened and the supply of the device to be protected is interrupted.

The now de-energized device can then cool down again. In this case, the thermally coupled to the device switch cools down again, which then automatically closes again. While such switching behavior protects e.g. A hair dryer can be quite useful, this is not desirable anywhere where the device to be protected after switching off may not automatically turn on to avoid damage. This is for example for electric motors, which are used as drive units.

In known temperature-dependent switches therefore often a so-called self-holding resistor is provided which is electrically parallel to the first terminals; see for example the DE 195 14 853 A1 , The self-holding resistor is electrically connected with the switch open in series with the device to be protected, through the because of the resistance value of the self-holding resistor now only a harmless residual current flows. However, this residual current is sufficient to heat the self-holding resistor so far that it emits a heat that holds the bimetallic snap disk above its switching temperature.

Notwithstanding the design of the switch according to DE 196 23 570 C2 The temperature-dependent switching mechanism may also comprise only a bimetallic snap-action disk which carries the movable contact part and thus carries the operating current.

The derailleur may also comprise a bimetallic spring tongue, as in the DE 198 16 807 A1 is described. This bimetallic spring tongue carries at its free end a movable contact part, which cooperates with a stationary counter contact. The stationary mating contact is electrically connected to one of the first terminals, wherein the other first terminal is electrically connected to the clamped end of the bimetallic spring tongue. The bimetallic spring tongue guides the operating current of the electrical device to be protected.

If the temperature-dependent switch is to carry particularly high currents, so often a current transfer member in the form of a contact bridge or a contact plate is used, which is moved by a spring member and carries two contact parts, which cooperate with two stationary mating contacts.

In this way, the operating current of the device to be protected flows from the first mating contact via the first contact part into the contact plate, through it to the second contact part and from this into the second mating contact. The spring part is thus de-energized. It is also known to use the spring member itself, so for example a bimetallic snap disk or a working against a bimetallic Federschnappscheibe as a contact bridge.

In particular, when the known switches are used for the protection of high-performance engines, they must because of in operation and in particular when starting the engines occurring strong shocks be mechanically very resilient.

Furthermore, the switches must be able to reliably protect the motors both in the limit mode with maximum allowable power and with a blocking rotor. To test whether the switch does this, usually two tests are performed.

In the so-called heating test, the motor is operated at maximum power, whereby neither the flow of current through the switch nor the heat transferred thereby from the motor to the switch may open the switch.

In contrast, in the so-called locked rotor test , the motor is connected to the operating voltage with the rotor locked , which results in an operating current flowing through the motor which is three to five times greater than the usual operating current.

Of course, this high current also leads to a heating of the motor and thus to an increase in temperature at the switch.

However, this heating takes place so slowly that the engine may already irreversibly destroyed before the switch starts due to the increase in engine temperature. Therefore, in this test, a heater resistor must cause the switch to open very quickly.

Even with a suitable coordination between the response temperature of the bimetallic snap disk and the resistance of the heating resistor alone, however, these two conflicting conditions in the known switches described above can not be met.

Although these values could be set so that the maximum allowable operating current does not cause the heating resistor, the bimetallic snap disk heated to a temperature above its switching temperature, but that this is done only by the much higher current at blocked rotor.

On the other hand, the response temperature of the bimetallic snap disk could be chosen to be above the temperature that the engine assumes at maximum allowable power during operation and transmits to the switch, but below the temperature to which the bimetallic snap disk is subjected by the heating resistor is heated when it is traversed by the current with blocked rotor.

However, the so set switching behavior is only achieved in static operation, so if enough time has elapsed, so that either opens at too high a temperature of the motor or too high current, the switch. To protect a powerful engine, it is also necessary that the switch starts extremely fast, especially with a blocking rotor.

This requires a very good thermal coupling of the heating resistor to the switch, so that a change in the temperature of the heating resistor is transmitted to the bimetallic snap disk in no time.

In addition to good thermal coupling, the switch must also meet the required number of switching cycles, which should be at least 3,000 for typical requirements as described above. For smaller operating currents up to approx. 4 amps and switching temperatures of approx. 160 ° C, the known switches also meet these requirements.

At higher operating currents of 10 and more amperes, however, the number of switching cycles is significantly reduced, because the temperature changes at the solder joints between base and support plate cause the solder joints are so much damaged due to fatigue fracture after about 1,000 cycles, so that the flow of current is interrupted and the switch is inoperative.

The DE 10 2011 016 133 B4 suggests therefore, in contrast to the construction of the aforementioned DE 43 36 564 C2 flat solder the bottom of the switch and not only the lateral transition between the bottom and side wall on the support.

The bottom of the switch serves two purposes, on the one hand, it lies on the entire surface of the heating resistor, on the other hand, it is held flat by material bond on the soldering surface. This flat material connection in addition to the heating resistor results in a very good thermal connection of the switch to the heating resistor, the switch is set in this way not only mechanically very stable on the support plate, this type of definition also leads to the desired thermal coupling.

DE-A1-4142716 discloses a temperature-dependent switch according to the preamble of claim 1.

In this known switch, the construction described so far involves the risk that, if improperly handled, a force is exerted on the carrier plate and / or the housing, which causes the solder joints to break or at least be weakened.

Based on this prior art, it is therefore an object of the present invention, the aforementioned switch in such a way that with a simple and inexpensive construction, a good thermal coupling of the heating resistor to the switch and at the same time a good mechanical hold between the switch and heating resistor is realized.

According to the invention this object is achieved in the switch mentioned above in that the heating resistor is formed as a sheet-metal part which is welded to the housing, wherein on the metal part, a further connection is provided.

By welding a designed as a sheet-metal part heating resistor is provided for a mechanically very stable connection between the housing and the heating resistor, after first attempts in the rooms the applicant even after more than 3,000 switching cycles at operating currents of 20 or 30 amps show no fatigue failure.

By welding, the thermal connection of the heating resistor to the housing is realized in a structurally simple and inexpensive manner. If the housing is current-conducting where the heating resistor is welded, the electrical connection to one of the first two connections is simultaneously produced by welding if the conductive housing either already serves as one of the first connections or according to the invention with one of the first Connections is connected. The other first terminal of the switch and a further connection provided on the heating resistor then serve the external connection of the switch, for example by soldering on connecting leads.

In the context of the present invention, "first connections" are understood to be the two connections of a switch via which it is electrically connected to a device to be protected if it is not provided according to the invention with an outer metal part which acts as a heating resistor and provides a further connection ,

The advantage in this case is in particular that the heating of the housing is effected by the flowing operating current with the aid of a welded metal part, whereby the current heat is distributed away from the switching contact points to the housing and to the rear derailleur.

By welding, the metal part is wavy, which speaks at first glance against the use of a welded externally to the housing metal part. However, according to the inventors, this resulting ripple makes it possible to use thin metal parts, because the current and heat do not occur over a large area over the entire metal part but over the welds of the heating resistor formed by the metal part into the housing.

With the outer metal part, switches with or without self-holding function can be equipped with a defined current sensitivity.

In the context of the present invention, a "sheet metal part" is understood to mean a flat and thin metal plate made of a suitable metal or suitable metal alloy with a corresponding electrical conductivity, which like a sheet metal part, in particular a thin sheet, is produced by rolling from suitable blanks. However, the sheet-metal parts can also be produced in other ways. In a simplified manner, the sheet metal part used according to the invention can also be referred to as a sheet metal part.

The problem underlying the invention is completely solved in this way.

In this case, it is preferred if the housing is designed to be electrically conductive at least in a section which is electrically connected to one of the first terminals, wherein the sheet metal or metal part is welded to the electrically conductive section, or if the housing as a whole is electrically conductive is.

Here it is advantageous that both the thermal and the electrical connection to the switch takes place by the welding process, which contributes to low manufacturing costs. The invention is therefore applicable to all switches, which have at least one current-carrying housing part or an electrically conductive housing or housing part, with which one of the first terminals is or can be connected.

The invention can therefore be used in existing switches, without the structure of the switch must be changed as such.

Further, it is preferred if the metal part is welded to the housing at at least two spot welds, preferably to the metal part as further connection a connection piece is welded, more preferably, the connection piece is welded to at least two welding points to the metal part.

By means of the spot-welded connections, the metal part can be fastened to the housing in a simple and inexpensive manner, the electrical and thermal connection being defined by the welding points, which is advantageous in particular when setting the resistance value of the metal part. Operating current and current heat are thus passed through the spot welds in the housing.

In this case, it is preferred if the metal part protrudes with a portion over the housing, on which the further connection is provided, wherein the further connection can also be arranged centrally or otherwise on the metal part.

Consequently, the further connection can either lie within the contour of the housing or laterally next to the floor or cover or above or below the housing. Depending on the respective applications can be based on the inventively welded to the outside of the housing metal part so the location of one of the external connections in a structurally simple and inexpensive way to choose arbitrarily.

Generally, it is preferred if the metal part measured between the further terminal and the housing or the welding points has an ohmic resistance value which is less than 100 mΩ, preferably between 2 and 50 mΩ, wherein preferably the metal part has a thickness which is at least 50 microns.

At the operating currents in the range of 10 amperes and higher, according to the findings of the present inventors, good current sensitivities are achieved with these values.

Given the dimensions of temperature-dependent switches and the resulting dimensions of the sheet-metal parts, these can be Set resistance values, if as sheet metal part z. B. spring band steel, eg 1.4310, or resistance alloys, eg Isachrom 2.4867, are used.

It is preferred if the derailleur comprises a bimetal snap-action disc which is mechanically connected to a movable contact part and presses below its switching temperature against a stationary contact part and lifts above its switching temperature of this, wherein the stationary contact part connected to one of the first terminals is, and the derailleur is connected at least when abutting contact parts with the other first terminal.

On the other hand, it is preferred if a spring snap-action disc, which biases the movable contact part in the sense of an abutment against the stationary contact part, and also a bimetal snap-action disc is provided, which lifts the movable contact part above its switching temperature of the stationary contact part, wherein further preferably the spring snap-action disc is arranged between stationary contact part and bimetal snap-action disc.

While it is quite sufficient, if only a bimetallic snap disk is provided, which performs both the operating current and the contact pressure and provides for the temperature-dependent opening, can by a spring-snap disk, in addition to the bimetallic snap-action or alone causes the contact pressure , The bimetallic snap disk are mechanically and electrically relieved in their low temperature position, which contributes to a greater long-term stability of their switching behavior.

Alternatively, it is preferred if the derailleur has a current transmitting member which cooperates with two stationary contact parts, which are each connected to one of the first terminals, wherein preferably one of the first terminals is electrically connected to the housing, further preferably the switching mechanism is a bimetallic snap disk includes, which is mechanically connected to the power transmission member and this presses below its switching temperature against the two stationary contact parts and lifts above their switching temperature of these, and further preferably, the derailleur comprises a spring washer which biases the power transmission member in the sense of a system against the stationary contact parts, wherein the bimetallic snap disk lifts the power transmission member above its switching temperature of the stationary contact parts.

Here it is advantageous that the switch can lead significantly higher currents than the above-mentioned switch, in which the current is passed through the bimetallic snap-action disc or through the spring snap-action disc. This is particularly advantageous when the switch is used to power powerful electric motors that require high operating currents.

Temperature-dependent switch with a current transmitting member, which cooperates with two stationary contact parts are, for example, from DE 26 44 411 A1 known. In these switches, the two stationary contact parts, which are arranged in the upper part, are connected in series with the supply current of the device to be protected, so that the current flows through the current transmitting member, when the switch is at a temperature below the switching temperature.

The power transmission member may be a separate contact plate, but it is also possible in individual cases, to use the bimetallic snap disk or the spring snap-action as a power transmission member.

In order to be able to use the above-described heating element formed as a metal part and the associated advantages, one of the two first connections is electrically connected to the electrically conductive lower part, which in turn is connected to the heating resistor, which is connected to the further connection. As a result, the current flows from the further terminal through the heating resistor into the lower part and from there via the first terminal to the second stationary contact part, from there through the current transfer member to the first stationary contact part and then via the first contact part to the other first terminal.

Due to the unusual at first glance interconnection of the second contact part and a first connection to the lower part, it is possible to use the advantages of formed as a metal part heating resistor for switches in which the operating current is not originally passed through the housing, but the housing is electrically conductive at least in a portion which is usually the lower part.

The inventive design of the heating resistor as a metal part can thus be used in all temperature-dependent switches having an electrically conductive housing part to which the metal part can be welded. The temperature-dependent switching mechanism can be constructed as desired, as long as it ensures that, depending on its temperature, it has an electrically conductive connection between the electrically conductive housing part, since it acts as one of the first connections or is connected according to the invention with one of the first connections, and the other first connection or opens.

In another embodiment of a switch, in which the housing of the switch, if it is not yet provided with the metal part, the operating current does not lead, the switch has an insulating base, on which the two first terminals are arranged, and on the the housing is attached, wherein preferably one of the two first terminals is electrically connected to the housing.

The switch can be additionally provided with a self-holding resistor, so that the open switch does not cool and automatically closes again.

Further advantages will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Fig. 1

einen schematischen, nicht maßstabsgetreuen Längsschnitt durch einen temperaturabhängigen Schalter, bei dem ein bewegliches Kontaktteil mit einem stationären Kontaktteil zusammenwirkt, und an dessen Gehäuse außen ein Heizwiderstand angeschweißt ist;

Fig. 2

in einer schematischen Ansicht den Schalter aus Fig. 1 von unten mit Blick auf den Heizwiderstand;

Fig. 3

in einer Darstellung wie in Fig. 1 einen weiteren temperaturabhängigen Schalter, bei dem zwei stationäre Kontaktteile mit einem Stromübertragungsglied zusammenwirken;

Fig. 4

den mit Anschlusslitzen versehenen Schalter aus Fig. 3 in Draufsicht;

Fig. 5

eine schematische Draufsicht auf einen weiteren temperaturabhängigen Schalter mit angeschweißtem Heizwiderstand; und

Fig. 6

eine schematische Draufsicht auf noch einen weiteren temperaturabhängigen Schalter mit angeschweißtem Heizwiderstand.

Embodiments of the invention are illustrated in the accompanying drawings and are explained in more detail in the following description. Show it:

Fig. 1

a schematic, not to scale longitudinal section through a temperature-dependent switch, in which a movable contact member cooperates with a stationary contact member, and on the housing outside a heating resistor is welded;

Fig. 2

in a schematic view of the switch Fig. 1 from below, looking at the heating resistor;

Fig. 3

in a representation like in Fig. 1 another temperature-dependent switch in which two stationary contact parts cooperate with a current transmitting member;

Fig. 4

the provided with pigtails switch off Fig. 3 in plan view;

Fig. 5

a schematic plan view of another temperature-dependent switch with welded heating resistor; and

Fig. 6

a schematic plan view of yet another temperature-dependent switch with welded heating resistor.

In Fig. 1 is denoted by a temperature-dependent switch 10, which includes a cup-shaped lower part 11 which is closed by an upper part 12 which is held with the interposition of an insulating film 13 by a flanged edge 14 on the lower part 11.

In the housing formed by the lower part 11 and upper part 12 of the switch 10, a temperature-dependent switching mechanism 15 is arranged, which is a Federschnappscheibe 16, which carries centrally a movable contact part 17, on which a freely inserted bimetallic disc 18 is seated.

The Federschnappscheibe 16 is supported on an inner bottom 19 inside of the lower part 11, which is made of electrically conductive material.

The movable contact member 17 is in abutment with a stationary contact member 20 which is provided on an inner side 21 of the upper part 12, which is also made of metal in this embodiment, although it is sufficient for the practice of the invention, if the housing at least in one Section is electrically conductive, in the switch 10 so at least the lower part 11 electrically conducts.

In this way, the temperature-dependent switching mechanism 15 in the in Fig. 1 shown low-temperature position an electrically conductive connection between the upper part 12 and the lower part 11 forth, the operating current via the stationary contact part 20, the movable contact part 17 and the spring snap disk 16 flows.

Alternatively, it is also possible, instead of the spring snap disk 18, to use directly a bimetallic part which carries the movable contact part 17 and thus conducts the operating current when the switch 10 is closed.

Increases in the switch 10 off Fig. 1 the temperature of the bimetallic disc 18 beyond its response temperature, so it snaps from the in Fig. 1 shown convex position in its concave position in which it lifts the movable contact member 17 against the force of the spring washer 16 of the stationary contact member 20 and thus opens the circuit.

Such a temperature-dependent switch 10 is for example from the DE 196 23 570 A1 The contents of which are hereby made the subject of the present disclosure.

As a first terminal 22 is used in the switch Fig. 1 a contact surface in a central region of the upper part 12. As a further first connection is the lower part 11, which can be contacted for example via the edge 14 or a bottom 26.

The switch 10 is equipped with a heating resistor 24 in the form of a metal part 25, which is externally welded to the outer bottom 26 of the lower part 11 and is electrically in series with the first terminals.

The metal part 25 is welded in the embodiment shown at four welds 27 to the outer bottom 26, which is preferably done by resistance welding. In Fig. 1 two of the four spot welds 27 can be seen.

Centered on the metal part 25, a contact surface is provided, which serves as a further connection 28 for the switch 10.

To the terminals 22, 28 can be soldered in a known manner depending on a terminal lug with its respective inner end, which then serve for interconnection with a device to be protected. For this purpose, welding angles can be welded to the connections 22, 28.

It is also possible to solder to the terminals 22, 28 pigtails.

The metal part 25 has between the terminal 28 and the lower part 11 - via the welding points 27 - an ohmic resistance, which is in Milliohmbereich.

As a metal part, any electrically conductive sheet-metal part can be used, which has the corresponding resistance value at the dimensions possible here, as will be explained in more detail below.

Via the welding points 27, the metal part 25 is connected both electrically and thermally to the lower part 11. During welding, the metal part 25, which in the exemplary embodiment shown has a thickness of 50 μm indicated at 29, waves to such an extent that only the welding points 27 contribute to the electrical and thermal contact with the lower part 11. The resulting ripple is in Fig. 1 indicated at 31.

The metal part 25 could also be welded laterally to the conductive lower part 11 if the floor 26 is to be kept free as a heat transfer surface.

Alternatively, it would also be possible for the metal part 25 to be externally welded onto the electrically conductive cover part 12, so that the connection 22 would be electrically connected in series with the connection 28 via the heating resistor 24. As a second connection, for example, then the edge 14 or the bottom 26 of the lower part 11 would be available.

If necessary, between the bottom 26 and metal part 25, an insulating layer can be arranged. However, this was not necessary in the switches 10 produced and tested according to the invention so far in the premises of the applicant.

If desired, the switch 10 may also be equipped with a self-holding function, that is, have a further resistor which is electrically parallel to the first terminals. For this purpose, for example, the cover part 12 is made of PTC thermistor, in which case the insulating film 13 is omitted without replacement, so that the cover part 12 forming PTC resistor is electrically connected to both first terminals 22 and 11/14. Such a switch is in the DE 195 17 310 A1 described.

Alternatively, a self-holding resistor designed as a thick-film resistor can also be arranged on the cover part, as described, for example, in US Pat DE 195 14 853 A1 is described. In the switch known from this document, the self-holding resistor is applied to the insulating film 13.

Fig. 2 shows a view of the circular bottom 26 of the switch 10 Fig. 1 , It can be seen that the four spot welds 27 in the four corners 32 of the metal part 25 are centered.

On the metal part 25, a welding angle 34 is fixed centrally with three welding points 33, to which a pigtail 35 is welded. Evident is also a second pigtail 36, which is electrically connected to the one first terminal 22.

The square metal part 25 has edge lengths 37 of 10 mm, resulting in a thickness 29 of 50 microns to a resistance of about 10 mΩ between the pigtail 35 and - via the welds 27 and 33 - the bottom 26 leads, if a metal part Spring band steel 1.4310 is used.

Endurance tests have confirmed that such a switch 10 with an applied DC voltage of 14 volts an operating current of 25 A at a shutdown temperature of 160 ° C for more than 3,500 switching cycles without malfunction survives. In the short term, the switch 10 also withstands an operating current of 35 A at a shutdown temperature of 400 ° C.

The metal part 25 may also have any other geometric shape, in particular, the welding angle 34 may also be welded off-center on the metal part. The metal part 25 may for example be rectangular, triangular, round, circular, oval or teardrop-shaped, wherein the welding angle 34 or an arbitrarily formed connection piece can be welded centrally or on the edge of the metal part 25, which can also project laterally beyond the bottom 26.

It is only important that the metal part measured between the other terminal 28 or here the welding angle 34 and the housing has an ohmic resistance of less than 100 mΩ, preferably about 10 mΩ.

In Fig. 3 is designated at 40 another temperature-dependent switch, like the switch 10 off Fig. 1 is provided with a heating element formed by a metal part.

The switch 40 includes a temperature-dependent switching mechanism 41 which is housed in a housing 42. The housing 42 has an upper part 43 made of insulating material, which closes an electrically conductive lower part 44 whose edge 45 defines the upper part 43 on the lower part 44.

For the purposes of the present invention, it is here the lower part 44, which forms the electrically conductive portion of the housing 42, on which the metal part 25 is welded.

The switching mechanism 41 comprises a spring snap-action disc 46 and a bimetal snap-action disc 47, which, together with the spring snap-action disc 46, is centrally penetrated by a pin-like rivet 48, by which these are mechanically connected to a current transfer member 49 in the form of a contact plate.

The spring snap-action disc 46 is clamped with its edge 51 between a circumferential shoulder 52 inside in the lower part 44 and a spacer ring 53, on which the upper part 43 rests with its inner side 54

The bimetallic snap disk 47 is supported with its edge 55 on an inner bottom 56 of the lower part 44.

The round, in the present case circular power transmission member 49 has in the direction of the upper part 43 a circumferentially circumferential, electrically conductive contact surface 57, which cooperates with two stationary contact parts 58, 59, which are arranged on the inner side 54 of the upper part 43.

The stationary contact parts 58, 59 are formed as inner heads of contact rivets 61, 62, which pass through the upper part 43 and end in outer sections 63, 64. Between the sections 63, 64 an insulating web 65 is provided.

At the two outer portions 63, 64 of the contact rivets 61, 62, a connecting piece 67 or 68 is respectively arranged with tabs 71 and 72, which serve as the first terminals of the switch 40.

The lower part 44 has an outer bottom 69, to which the heating element 24 forming metal part 25 is welded with four welds 27, as described above for the switch 10.

In Fig. 3 again, the corrugation 31 and the connection 28 forming during welding can be seen.

The metal part 25 could also be welded laterally to the conductive lower part 44, if the bottom 69 is to be kept free as a heat transfer surface.

At the connection 28, the welding angle 34 may be welded to the base 69 before welding the metal part 25, as shown in FIG Fig. 2 has been described. In the bottom view, the switch 30 looks like the switch 10, so that in this respect to avoid repetition Fig. 2 is referenced.

To provide the switch 40 with pigtails, the upper, U-shaped tabs 71, 72 are folded down on the sections 63 and 64 and inserted into the form of "tunnel" usually stripped ends of the pigtails and soldered.

In the present case, however, a pigtail 73 is soldered only to the tab 71, as in the plan view of Fig. 4 is shown.

The tab 72 associated with the second stationary contact part 59 is electrically connected in a comparable manner to a connecting part 74 which is connected to the conductive lower part 44 via its edge 45. In the simplest case, the connecting part 74 is formed by solder, which connects the edge 45 electrically and mechanically to the connector 68.

In this way, the stationary contact part 59 is connected to the electrically conductive lower part 44, which is connected via the welding points 27 to the heating resistor 24, to which via the welding angle 34, a second pigtail 75 is connected, as in the plan view of Fig. 4 is indicated. The heating resistor 24 is thus electrically in series with the stationary contact part 59th

When the power transmission member 49 in Fig. 3 is in contact with the two stationary contact parts 58, 59, thus there is a continuous electrically conductive connection from the first pigtail 73 via the connector 67 to the first stationary contact part 58, from there via the current transfer member 49, the second stationary contact part 59, the second Connecting piece 68 and the connecting part 74 to the edge 45 and from there to the lower part 44, which is connected via the heating resistor 24 with the second pigtail 75.

When the lid member 43 is made of PTC resistor, the PTC resistor thus formed is parallel to the first terminals 71, 72 and provides a self-holding function, as it is known from DE 198 27 113 A1 is known.

Alternatively, according to the DE 198 27 113 A1 the self-holding resistor is also provided on the inside or outside of the cover part 43 made of insulating material and may be designed, for example, as a thick-film resistor.

Fig. 5 shows a plan view of a further embodiment of a switch 80 which is equipped with a heating resistor 24 in the form of a metal part 25.

The switch 80 has an insulating base 81 from which two connection electrodes 82, 83 protrude as connections. The base 81 is inserted in a metallic, electrically conductive housing 84, which is pushed onto the base 81 as a cap. At the base 81 is an in Fig. 5 held by the housing 84 concealed, temperature-dependent switching mechanism, as for example in the DE 195 09 656 A1 , of the DE 10 2004 036 117 A1 , of the DE10 2008 031 389 B3 or the DE 10 2011 016 896 B3 is shown.

Depending on its temperature, the switching mechanism establishes an electrically conductive connection between the two connection electrodes 82, 83 or opens the electrical connection.

In order to provide the switch 80 with a defined current dependence, the metal part 25 is welded to the housing 84 at the welding points 27, as described above for the switches 10 and 40. At the soldering angle 34, a connection electrode 85 is welded in this embodiment.

The connection electrode 83 is electrically connected to the housing 84 via a connection part 86; the connecting part 86 fulfills the same function as the connecting part 74 in the case of the switch 40 Fig. 4 , The connecting part 86 is in Fig. 5 shown only schematically, it may take any suitable configuration.

It is understood that instead of the connection electrodes 82, 83, 85 and pigtails can be used. Then it may be possible to dispense with the connecting part 86 and one of the two existing at the switch as the first terminals leads are connected directly to the housing.

The heating resistor 24 is thus connected via the housing 84, the connecting part 86, the connecting electrode 83 and the temperature-dependent switching mechanism electrically in series between the two first terminals in the form of the connection electrodes 82 and 85. It serves in a similar manner as in the switch 40 for a defined current-dependent switching.

Regardless of the nature and structure of the temperature-dependent switching mechanism can be equipped in the manner described temperature-dependent switches with two first terminals, between which the switching mechanism temperature-dependent electrical connection, and in at least one section electrically conductive housing by the inventively used metal part with a current-dependent switching function ,

If the switch as such already switched depending on the current, this switching function can be designed and improved defined by the metal part used in the invention.

While in the embodiments of the Fig. 1 to 5 the further connection 28 is arranged below the switch 10, 40, 80, that is to say within its contour Fig. 6 a plan view of an embodiment in which the metal part 25 projects laterally beyond the bottom 26 of the switch 10. One pigtail 91 is soldered to the first terminal 22, another pigtail 92 to the other terminal 28.

The metal part 25 is also welded to the outside of the bottom 26 of the switch 10, as in Fig. 1 and 2 is shown.

The metal part 25 has here teardrop shape, and the further connection 28 is in the embodiment of Fig. 6 not centrally on the metal part 25 but on a portion 93 of the metal part 25, which forms, so to speak, the outlet of the drop, that is, where the metal part 25 projects laterally beyond the switch 10.

Claims (18)

1. Temperature-dependent switch comprising a temperature-dependent switching mechanism (15; 41), a housing (11, 12, 42; 84) accommodating the switching mechanism (15; 41), two first connections (22, 14, 26; 63, 64; 82, 83) provided on the switch (10; 40; 80), between which first connections the switching mechanism (15; 41) makes or interrupts an electrically conductive connection depending on the temperature of said switching mechanism, and comprising a heating resistor (24), which is arranged on an outside of the housing (11, 12; 42, 84) and is connected electrically in series with the two first connections (22, 14, 26; 71, 72; 82, 83),
   characterized in that the heating resistor (24) is embodied in the form of a sheet-like metal part (25), which is welded to the housing (11, 12; 42; 84), wherein a further connection (28) is provided on the metal part (25).
2. Switch according to Claim 1, characterized in that the housing (11, 12; 42, 84) is designed to be electrically conductive at least in one section (11; 44), which is electrically connected to one of the first connections (22, 14, 26; 71, 72; 82, 83), and in that the metal part (25) is welded to the electrically conductive section (11; 44).
3. Switch according to Claim 1 or 2, characterized in that the housing (84) is designed to be electrically conductive as a whole.
4. Switch according to anyone of Claims 1 to 3, characterized in that the metal part (25) is welded to the housing (11, 12; 42, 84) at at least two welding spots (27).
5. Switch according to anyone of Claims 1 to 4, characterized in that a connection piece (34) is welded to the metal part (25) as further connection (28).
6. Switch according to Claim 5, characterized in that the connection piece (34) is welded to the metal part (25) at at least two welding spots (33).
7. Switch according to anyone of Claims 1 to 6, characterized in that the metal part (25) protrudes with a section (93) beyond the housing (11; 12), on which section the further connection (28) is provided.
8. Switch according to anyone of Claims 1 to 6, characterized in that the further connection (28) is arranged centrally on the metal part (25).
9. Switch according to anyone of Claims 1 to 8, characterized in that the metal part (25) has an ohmic resistance value of less than 100 mΩ, preferably between 2 and 50 mΩ, measured between the further connection (28) and the housing (11, 12; 42, 84).
10. Switch according to anyone of Claims 1 to 9, characterized in that the metal part (25) has a thickness (29) of at least 50 µm.
11. Switch according to anyone of Claims 1 to 10, characterized in that the switching mechanism (15) comprises a bimetallic snap-action disc (18), which is mechanically connected to a movable contact part (17) and, when below its switching temperature, presses said movable contact part against a stationary contact part (20) and, when above its switching temperature, lifts off said movable contact part from said stationary contact part, wherein the stationary contact part (20) is connected to one of the first connections (22), and the switching mechanism (15) is connected to the other first connection (11, 14, 26) at least when the contact parts (17, 20) rest on one another.
12. Switch according to Claim 11, characterized in that a spring disc (16) is provided which preloads the movable contact part (17) for resting on the stationary contact part (20), wherein the bimetallic snap-action disc (18) lifts off the movable contact part (17) from the stationary contact part (20) when above its switching temperature.
13. Switch according to anyone of Claims 1 to 10, characterized in that the switching mechanism (41) has a current transfer element (49), which interacts with two stationary contact parts (58, 59) which are each connected to one of the first connections (71, 72).
14. Switch according to Claim 13, characterized in that one of the first connections (72) is electrically connected to the housing (42).
15. Switch according to Claim 12 or 13, characterized in that the switching mechanism (41) comprises a bimetallic snap-action disc (47), which is mechanically connected to the current transfer element (49) and presses said current transfer element against the two stationary contact parts (58, 59), when below its switching temperature, and lifts said current transfer element off from said stationary contact parts, when above its switching temperature.
16. Switch according to Claim 15, characterized in that the switching mechanism (41) comprises a spring disc (46), which preloads the current transfer element (49) for resting against the stationary contact parts (58, 59), wherein the bimetallic snap-action disc (47) lifts off the current transfer element (49) from the stationary contact parts (58, 59), when above its switching temperature.
17. Switch according to anyone of Claims 1 to 10, characterized in that it comprises an insulating base (81), on which the two first connections (82, 83) are arranged and onto which the housing (84) is plugged.
18. Switch according to Claim 17, characterized in that one of the two first connections (83) is electrically connected to the housing (84).

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