EP0920044A2 - Switch with a temperature sensitive switching mechanism - Google Patents

Abstract

The switch has a housing (12) for the temp. dependent switching mechanism (11) with a first housing part (15) with a first electrode (24) on its inner floor and connected to a first external connection. A second housing part (22) connected to the first part contains a second electrode (20) connected to the second external connection. The switch mechanism makes an electrical connection between the electrodes depending on its temp. A parallel resistance (33) in form of a PTC module is connected geometrically and electrically between the two electrodes in the housing.

Description

The present invention relates to a switch with a temperature-dependent rear derailleur housing, the one first housing part, on the inner bottom one with a first External connection connected first electrode is arranged, and a second housing part which closes the first housing part which has one connected to a second external connection comprises second electrode, the switching mechanism depending an electrically conductive connection from its temperature between the first and the second electrode.

Such a switch is known from DE 196 09 310 A1.

In the known switch, the first housing part is made of insulating material manufactured, in which the first electrode by injection molding or embedded potting as an integral part is. This first housing part is replaced by a second housing part in the form of an electrically conductive material Bottom closed, the inside as a second electrode works.

Both electrodes are, so to speak, disc-shaped sheet metal parts which are integrally formed approaches that are external connections serve the switch. The bottom part lies on it a shoulder of the first housing part and is replaced by a hot stamped ring held on this.

Between the two electrodes is so formed inside Housing arranged a conventional bimetal rear derailleur, the Spring washer is supported with its edge on the bottom part and the movable contact part carried by her below the Switching temperature against an inwardly projecting counter contact on the other electrode. About the mobile As usual, the contact part is fitted with a bimetal snap disc, which is free of forces below its switching temperature and in the event of a temperature increase beyond its switching point movable contact part against the force of the spring washer Counter contact lifts off and thereby the electrical connection between the two external connections opens.

The known switch described so far is extremely robust and has very small external dimensions, which is why it is not only universal but can be used especially where little Assembly space is available, e.g. in coils of transformers or electric motors. This is over the bottom part Switch thermally very well coupled to a device to be monitored, so that an increase in temperature of the device itself transfers to the inside of the switch and there to one corresponding increase in the temperature of the bimetallic snap disc leads. Such switches are in series between that device to be protected and a power supply switched, so that the operating current of the device to be protected by the Switch flows, this current in the event of an impermissible temperature increase consequently switches off.

However, it is often necessary to add to the temperature of the protective device also adhering to the operating current a certain upper limit to monitor the device already to be able to switch off before the temperature increase begins. This is particularly common with electric motors before that due to external influences the rotor stands or spins very slowly, which initially leads to an increase in the Operating current leads, which in turn increases the temperature of the device. If now the increased Current flow leads to a shutdown of the device, so the inadmissible temperature increase completely avoided, which of course is an advantage.

This protective function of a switch with temperature-dependent Switchgear is called "current-dependent" switching and therefore causes a series resistor to be in series with the rear derailleur is switched, which is also from the operating current of the protective device is flowed through. By choosing the resistance value this series resistance and its thermal Coupling to the switch leads to a certain current flow through the switch and thus the series resistance to development a certain amount of heat, which in turn switches and so that the bimetallic snap disc is heated in a defined manner. On the Resistance value can therefore be an upper limit for the operating current be predetermined. If the operating current exceeds this Value, so is developed by that in the series resistance Heat the bimetal snap disc above its switching temperature addition, so that the switch opens before the device to be protected has warmed up inadmissibly.

Such a switch is known from DE 43 36 564 A1. This switch initially comprises an encapsulated bimetallic switching mechanism, that housed in a two-piece metal case is, as is known for example from DE 21 21 802 A1.

This encapsulated switch is now placed on a ceramic support, on which there is a thick film resistor, the via conductor tracks with the conductive lower part of the encapsulated Derailleur is connected. The other end of the resistance is connected to a solder pad to which a first lead is soldered. The second strand is electrical conductive cover part of the encapsulated rear derailleur soldered.

Although the known switch is satisfactorily a current dependent Switching enables and at the same time temperature monitoring allowed, it has a number of disadvantages.

On the one hand, the ceramic carrier cannot be mechanically loaded, Hairline cracks occur during transport as bulk goods Incoming inspection can only be recognized with a microscope can. Loosen by soldering the wire to the ceramic carrier often the conductor tracks. Because of this problem is a increased control and inspection effort required, the pricing of the product to the appropriate height. Another The disadvantage is the low pressure stability of this construction, those for wrapping in transformer windings or electric motors is not suitable.

On the other hand, this well-known switch is widely used, because the application of a resistor with a defined resistance value a well-mastered technique on a ceramic carrier is, here e.g. Thick film resistors used.

Another function with temperature-dependent switches what is desired is the so-called self-retention, in which a Parallel resistance when the switchgear is open from a residual current through which there is sufficient warmth, to keep the rear derailleur open. When closed Switching mechanism, the parallel resistance is bridged by this, so that it now has no function. However, the rear derailleur opened because either the temperature of the device or the temperature of a series resistor due to an increased Operating current have led to the bimetallic snap disk jumps over, the parallel resistance now takes over a residual current and consequently develops a sufficient one Warmth to keep the rear derailleur open. This will make a Repeated clocking of the switch prevented after cooling the switch of the protected device cannot close again, which could cause the device to warm up again inadmissibly.

The choice of the resistance values of parallel resistance as well as Series resistance is such that the series resistance is one takes on a very low ohmic value in order to keep the current flowing as possible little to influence, while the parallel resistance one has significantly greater value to the strength of the residual current to be clearly limited, i.e. the device against an excessive operating current to protect.

Such a self-holding function is also off the switch known from DE 43 36 564 A1. There is on a PTC component is provided on the ceramic carrier, which has one end with the second connecting wire and other end with conductor tracks is soldered to the lower part of the encapsulated rear derailleur are connected.

In this way, the PTC device is electrically parallel to that two-part, encapsulated housing and thus to the temperature-dependent Rear derailleur arranged so that it is closed Switchgear state is bridged by this and it in the open Condition of the rear derailleur is heating up.

In the known switch, the self-holding function is also satisfactory realized, but it can be manufacturing technology conditional problems occur when the known switch is not assembled by specialists. So it is known that when soldering PTC components influences their temperature curve due to improper soldering also mechanical Damage to the PTC module can be caused.

The manufacture of the known switch is therefore not only very wage-intensive, with the use of temporary workers can also be a appropriate committee appear.

Against this background, it is an object of the present invention to further develop the switch mentioned at the beginning, that it is structurally simple with at least one other Function is provided.

In the switch mentioned above, this object is achieved according to the invention solved in that in the housing geometrically and a parallel resistor electrically between the two electrodes is arranged.

The object underlying the invention is achieved in this way completely solved.

The inventor of the present application has recognized that that it is not necessary to have the parallel resistance outside to arrange the housing of the switch on a separate carrier, but that this is both electrical and geometric can be placed between the two electrodes. Of the Parallel resistance is therefore no longer accessible from the outside, thus protected from mechanical influences. Another advantage is that separate soldering measures as in the state the technology for the parallel resistance are not required, so that shifts in the temperature curve of a PTC module be avoided.

The inventor of the present application has recognized that the PTC module still in the housing of the generic switch can be integrated because a PTC module with clearly smaller dimensions can be used if between parallel resistance and temperature-dependent switchgear no two-piece metal housing is available. The PTC module is only make sure that it has a height of at least 2 mm, thus the required distance for dielectric strength remains between the two electrodes.

In one development, it is preferred if the first housing part is made of insulating material in which the first Electrode is held captive, and if in the first housing part a through opening is provided which itself extends from the first to the second electrode and one PTC module that acts as a parallel resistor with both Electrodes is connected.

The advantage here is that the insulation of the PTC module, so to speak is done automatically, during the manufacture of the new switch just a piece of PTC ceramic in the intended Opening must be inserted, which in the end is already is closed by the integral first electrode. After that the second electrode is attached, causing the opening too is closed on the second side and at the same time one Can be contacted with the PTC block. All in all the new switch can be installed very easily, at the previous manufacturing process for the generic Switch should only be provided as a further step, where the PTC module is inserted into the opening. Another change must be made when manufacturing the housing Insulating the tool to be changed so that the opening is created automatically.

It is then preferred if on one of the two electrodes a spring tongue is provided which opposes the PTC module the other electrode presses.

This measure has the advantage that reliable contacting of the PTC module with both electrodes, wherein is prevented by the spring force of the spring tongue on the PTC component has been subjected to excessive mechanical loads become.

The new switch now makes them state of the art known in connection with the soldering of PTC components Disadvantages avoided, because the PTC module is neither electrically influenced mechanically while being electrical and is geometrically arranged between the two electrodes.

It is further preferred if the first electrode is in the first Housing part by casting or injection molding during manufacture of the housing part is held so captive that it is integral Is part of this housing part, preferably the second housing part is an electrically conductive base part whose inner bottom acts as a second electrode.

These measures are in themselves in the switch mentioned above already realized, they enable a very pressure-resistant, easy to manufacture housing with small dimensions. In that out Insulating material manufactured housing part in which the first electrode is now only the PTC component has to be embedded be inserted before the base part is then mounted , which means that the PTC module is automatically electrically connected to both Sides is contacted. This way, a switch can both can be manufactured with and without self-retention, whereby in the latter does not apply to the insert surface for the PTC module is occupied. This has the advantage that different Products with completely different functions and applications the simple omission or addition of a component via can run the same production machines. This was previously not possible because the integration of resistors for the Self-holding always complex special adaptations or constructions has required.

In a further development, it is preferred if the switch comprises a ceramic support which points towards the switching mechanism is arranged on one of the two electrodes and a series resistor wearing one end with the electrode and another Is connected to a mating contact for the rear derailleur, preferably the first electrode one on the switching mechanism Has to be facing flat surface to which the ceramic carrier is attached and with which the series resistor is electrically connected is.

This measure is structurally advantageous for series resistance as well as its geometrical arrangement will be well mastered Ceramic technology used on the one well adjustable Series resistance is arranged. But now there are none More wire must be soldered to the ceramic carrier and he also is mechanically protected by the housing, a very thin supports are used, so that the outer dimensions of the known switch can not be changed or only slightly changed have to.

Instead of the previous protruding counter contact at first electrode now uses a flat surface on which the Ceramic carrier is placed. Because of the planned edition of the Ceramic carrier hardly loaded mechanically by the rear derailleur, see above that this including the series resistance provided on it and the counter contact arranged on it none must have a greater thickness than the counter contact in the State of the art switches. However, this means that the switch can maintain its original dimensions, whereby only the first electrode has a different shape must be provided with a flat surface instead of the counter contact, to which the ceramic support is attached. The ceramic support can be a through-hole for the series resistor have and so glued to the flat surface that the Plating through electrically at the same time with this electrode is contacted.

On the other hand, however, it is preferred if the ceramic carrier has at least one preferably laser-perforated through hole, through which he soldered to the electrode and the Series resistor is electrically connected to this.

This measure is constructively advantageous, because it is only one operation required to both mechanical and also establish the electrical connection. The laser-punched Through holes are made using a secured procedure manufactured in which the ceramic carrier does not jump, so that of the prior art in connection with ceramic carriers and their reprocessing recurring high rejects is avoided. In addition, these ceramic supports can be used instead of Bulk goods can still be delivered in a magazine to prevent further damage to avoid the ceramic carrier.

It is further preferred if the switching mechanism is electrically conductive spring washer, which includes a movable contact part wearing and working against a bimetallic snap disc, which sits approximately in the middle on the movable contact part, whereby the spring washer with its edge on one electrode supports and the movable contact part against the other electrode presses when the rear derailleur is below its response temperature located.

This measure is also known per se and enables it a self-aligning bimetal rear derailleur, in which the Bimetallic snap disc below its switching temperature free of forces is, so that the switching temperature by mechanical Cannot shift load. In connection with the ceramic support this gives the further advantage of simple Contacting the series resistor. As mentioned earlier, is this one end with the first electrode and others End connected to a counter contact on which the spring washer presses the movable contact part so that the series resistance electrically in series between the first electrode and the Spring washer is connected, which in turn with the second electrode is connected so that between the two external connections the switch is now connected in series from a series resistor and bimetal rear derailleur is arranged.

According to the invention, the generic switch can on the one hand can be provided with a parallel resistor, which in a Through hole of the insulating material housing is inserted and is in contact with the electrodes at both ends, on the other hand additionally a series resistor due to the ceramic plate can be provided for the current-dependent switching worries. This enabled the generic switch to be surprising be trained in such a simple way that without extensive Changes to his manufacturing process a self-holding function and possibly also a current-dependent switching is provided become.

Further features and advantages result from the description and the attached drawing.

It is understood that the above and those below Features to be explained not only in the specified Combination, but also in other combinations or can be used alone, without the scope of to leave the present invention.

Fig. 1

den neuen Schalter in einer schematischen Schnittdarstellung längs der Linie I-I aus Fig. 2; und

Fig. 2

eine Draufsicht auf den Schalter aus Fig. 1.

An embodiment of the invention is shown in the accompanying drawing and is explained in more detail in the following description. Show it:

Fig. 1

the new switch in a schematic sectional view along the line II of Fig. 2; and

Fig. 2

a plan view of the switch of FIG. 1st

In Fig. 1 is a schematic side view of a new one Switch 10 shown, the temperature-dependent switching mechanism 11 comprises, which is arranged in a housing 12.

The housing 12 has an electrically conductive bottom part 14 and a cup-like cover part 15 made of insulating material, which contains an annular space 16, in which the temperature-dependent Switch 11 is inserted.

The switching mechanism 11 comprises a movable contact part 17 which is supported by a spring washer 18 and a bimetallic snap disk 19 is laid.

The electrically conductive bottom part 14 forms with its inside an electrode 20 on which the spring washer 18 with supports its edge 21. The disc-shaped bottom part 14 goes integrally into a first outer terminal 22, which is thus electrical conductive with the spring washer 18 and thus with the movable Contact part 17 is connected.

A second outer connection 23 of the switch 10 is integral with an overmolded electrode 24 connected to an inner Bottom 15a of the lid part 15 is arranged. The cover part 15 is injected around the likewise disk-shaped electrode 24, so that it is captively embedded in the cover part 15 is. The arrangement is such that the electrode 24 a plane surface 25 to be pointed at the switching mechanism 11 has, on which a ceramic disc 26 is arranged, the one fixed counter contact 27 for the movable contact part 17th wearing.

The ceramic disk 26 has laser-perforated passages 28, via which they are connected to the electrode 24 with the aid of soldering points 29 is attached. In a manner to be described, between the Soldering points 29 and the counter contact 27 a series resistance arranged.

This arrangement means that it lies between the two external connections 22, 23 a series connection of switching mechanism 11 and series resistance. In the switching state shown in Fig. 1 the bimetal snap disk 19 is below its switching temperature, so that the spring washer 18 the movable contact part 17 presses against the fixed counter contact 27, so that the Switchgear 10 flowing operating current of a to be protected electrical device flows through the series resistor and heats up. Depending on the resistance value of the series resistance as well as the strength of the flowing current heats the Ohmic heat developed in the series resistor Fig. 1 force-free bimetallic snap disk 19 so far that it against the force of the spring washer 18, the movable contact part 17 from the fixed counter contact 27 and thus the current interrupts.

It should also be mentioned that the electrode 24 with its flat surface 25 points into an annular space 30 into which after the injection the electrode 24 into the cover part 15, the ceramic disk 26 is inserted, whereupon through the soldering points 29 both a mechanical as well as an electrical connection to the Electrode 24 is made. Then the rear derailleur 11 in the annular space 16 is inserted, whereupon the base part 14 is then placed and attached to the cover part 15 by an edge 31 becomes.

In addition to the switching mechanism 11, the cup-like cover part 15 a parallel resistor 33 is provided, the geometric and electrical is arranged between the two electrodes 20, 24 and ensures a self-holding function, as already mentioned at the beginning has been described.

A continuous opening 34 is provided in the cover part 15, which extends between the two electrodes 20, 24 and picks up a PTC chip 35 at both ends is electrically connected to the electrodes 20, 24. At the A spring tongue 36 is provided for this purpose, which protrudes into the opening 34 and the PTC module 35 against the upper electrode 24 presses. The spring force of the spring tongue 36 is set so that on the one hand for a safe electrical contact to the two electrodes 20, 24 is provided on the other hand, the PTC component is not mechanically excessive is charged.

FIG. 2 shows a top view of the switch from FIG. 1, where a series resistor 38 is now also indicated schematically is that via a conductor track 39 with the fixed counter contact 27 and via conductor tracks 40 and 41 with the solder points 29 is electrically connected. The series resistor 38 is a usual thick-film resistance, which is known and good mastered techniques arranged on the ceramic disc 26 , its resistance value being extremely precise as needed can be set, whereby the switch 10 leading operating current can be precisely selected.

Furthermore, the PTC module 35 is shown schematically, the between the two electrodes 20, 24, which is dashed in Fig. 2 to be seen as extensions of the external connections 22 and 23 are.

Returning to FIG. 1, it should also be noted that the Ceramic disc 26 arranged series resistor 38 and the Parallel resistor 33 both electrically and geometrically between the electrode 24 and the switching mechanism 11 or between the two electrodes 20, 24 arranged inside the housing 12 are.

Claims (9)

Switch with a temperature-dependent switching mechanism (11) accommodating housing (12), which has a first housing part (15), on the inner bottom (15a) of which a first electrode (24) connected to a first outer connection (23) is arranged, and a comprises a first housing part (15) which closes a second housing part (14) which comprises a second electrode (20) connected to a second external connection (22), the switching mechanism (11) depending on its temperature having an electrically conductive connection between the first and the produces a second electrode (24, 20),
characterized in that a parallel resistor (33) is arranged in the housing (12) geometrically and electrically between the two electrodes (24, 20). Switch according to claim 1, characterized in that the first housing part (15) is made of insulating material, in which the first electrode (24) is held captive, and that in the first housing part (15) a continuous Opening (34) is provided which extends from the first to the second electrode (24, 20) and a PTC module (35), which acts as a parallel resistor (33) is connected to both electrodes (24, 20). Switch according to claim 2, characterized in that on one (20) of the two electrodes (24, 20) has a spring tongue (36) is provided, which the PTC module (35) against the other electrode (24) presses. Switch according to one of claims 1 to 3, characterized in that that the first electrode (24) in the first housing part (15) by casting or injection molding at the Manufacture of the housing part (15) held captive is that they are an integral part of this housing part (15) is. Switch according to claim 4, characterized in that the second housing part (14) an electrically conductive bottom part (14), the inner bottom of which acts as a second electrode (20) works. Switch according to one of claims 1 to 5, characterized in that that the switching mechanism (11) is an electrically conductive Spring washer (18) which comprises a movable contact part (17) and works against a bimetallic snap disc (19), the middle of the movable contact part (17) sits, the spring washer (18) with her Edge (21) is supported on an electrode (20) and the movable Contact part (17) against the other electrode (24) presses when the rear derailleur (11) is below its response temperature located. Switch according to one of claims 1 to 6, characterized in that that it comprises a ceramic support (26) on the switching mechanism (11) facing one of the two electrodes (24, 20) is arranged and a series resistor (38) carries one end with the electrode (24) and the other End with a counter contact (27) for the rear derailleur (11) is connected. Switch according to claim 7, characterized in that the first electrode (24) facing the switching mechanism (11) Has flat surface (25) on which the ceramic carrier (26) attached and with the series resistor (38) electrically connected is. Switch according to claim 7 or 8, characterized in that the ceramic carrier (26) at least one preferably laser-perforated Through hole (28, 29) through which through it soldered to the electrode (24) and the series resistor (34) is electrically connected to it.

Images