EP2126948A1

EP2126948A1 - Thermal fuse for use in electric modules

Info

Publication number: EP2126948A1
Application number: EP08708253A
Authority: EP
Inventors: Norbert Knab; Georg Schulze-Icking-Konert; Thomas Mohr; Stefan Kotthaus; Nikolas Haberl; Stefan Stampfer; Michael Mueller
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2007-03-26
Filing date: 2008-01-28
Publication date: 2009-12-02
Also published as: DE102007014339A1; CN101647080A; US20100073120A1; WO2008116675A1; JP2010522418A

Abstract

The invention relates to a thermal fuse, especially for use in an electric module in the automotive field, comprising a connecting element (4, 25), which is electrically and mechanically connected to multiple connector points in order to provide a permanent and electrically conductive connection, and an actuator (6) which is configured separately from the connecting element (4, 25) and triggers without absorbing electrical energy when an ambiant temperature reaches a trigger temperature, thereby mechanically interrupting the electrical connection formed by the connecting element (4, 25).

Description

Thermal fuse for use in electrical modules

The invention relates to thermal fuses for use in electrical modules, in particular for high-current applications.

In order to protect electrical modules against overheating, irreversible thermal fuses are required, which interrupt (trigger) a current-carrying conductor if the ambient temperature is too high. The thermal fuses are designed so that the triggering temperature is not achieved due to a current flow, so that it is ensured that they can not be triggered by a high current, but only by an excessively high ambient temperature. Thus, a thermal fuse serves to provide an independent shutdown path for electrical modules which are at impermissibly high temperatures in the module, e.g. due to component failures, short circuits, e.g. due to external influences, malfunctions of insulating materials and the like. safely interrupts the flow of electricity.

Conventional thermal fuses are usually based on the concept of a fixed spring, such as a spring. a soldered leaf spring. In this case, even in the unreleased case, a mechanical force is permanently exerted on the joint, which leads to quality problems, especially in long periods of use, such as. long operating times in the automotive sector. In particular, a disruption of the solder joint may occur after a certain time.

It is therefore an object of the present invention to provide a thermal fuse which reliably interrupts a current flow and which has high reliability and long-term stability. Furthermore, it should be ensured that the thermal fuse triggers only dependent on the ambient temperature and not on the flowing current, so that even disturbances that only lead to current flows that are smaller than the permissible maximum currents can be reliably detected.

This object is achieved by the thermal fuse according to claim 1.

According to one aspect, a thermal fuse, in particular for use in an electrical module in the automotive sector, is provided. The thermal fuse comprises a connecting element which is electrically and mechanically connected to connection points in order to provide a permanent, electrically conductive connection via the latter, and an actuator formed separately from the connecting element which triggers without receiving electrical energy when an ambient temperature is a triggering temperature achieved, and thereby interrupts the electrical connection formed by the connecting element in a mechanical manner.

The thermal fuse has the advantage that due to the separate formation of connecting element and actuator triggering the thermal fuse is substantially independent of the current flowing through the current flowing through the connecting element current but depends only on the ambient temperature of the thermal fuse. Furthermore, with the above structure, it is possible to dispose the connecting member between the terminals without bias, so that a danger of degradation of the contacting of the connecting member at the terminals can be reduced.

Furthermore, the actuator may be provided with a stamp, which in the event of a triggering in the direction of Verbindungselemen- Tes is movable, thereby to solve the electrical connection.

According to one embodiment, the actuator may be formed with a cutting mechanism for triggering the

Cut through connecting element. For this purpose, the connecting element can be designed as a current-conducting flat conductor, in particular as a foil or sheet. In particular, the flat conductor may be provided with a predetermined separation point.

Furthermore, the connection points can be arranged on line regions of a stamped grid. The actuator is preferably arranged on a carrier element that is mechanically connected to the rod grid in order to determine an alignment of the actuator with respect to the connecting element.

According to one embodiment, the actuator comprises one or more mutually reacting materials, which are separated from each other by a fusible partition wall, wherein the melting temperature of the partition corresponds to the triggering temperature, wherein the actuator is arranged on the connecting element, that in the case of release, a volume change due to the reacting with each other Materials breaks the electrical connection formed by the connecting element breaks. In particular, the connecting element may be connected at the connection points by a material which can be melted at a melting temperature, the melting temperature of the fusible material being equal to or less than the triggering temperature.

Furthermore, the connecting element can either be fixedly connected to each of the connection points or can be used with the aid of a material which can be melted at a melting temperature. be bound, wherein the melting temperature of the fusible material is equal to or less than the triggering temperature.

In one embodiment, the plunger of the actuator is biased and held by a fuser, wherein the fuser is arranged to melt and release the biased punch when the ambient temperature reaches the firing temperature.

Further advantageous embodiments of the invention are specified in the dependent claims.

Preferred embodiments of the invention are explained below with reference to the accompanying drawings. Show it:

Fig. 1 is a schematic cross-sectional view of a first embodiment of a thermal fuse;

FIG. 2 shows a schematic representation of a cross section of a second embodiment of a thermal fuse; FIG. 3 is a cross-sectional view of an actuator for a thermal fuse according to the first or second embodiment;

4a to 4c are schematic representations of a cross section of a thermal fuse according to a third embodiment before the triggering, during the triggering or after the triggering.

In Fig. 1, a first embodiment of a thermal fuse is shown schematically. The thermal fuse is located in a stamped grid 1 between two line areas 2. The line areas 2 each have a connection point 3. The connection points 3 are connected via a flat conductor, e.g. a current-conducting foil 4 or a sheet, e.g. made of Cu or another conductive material, connected to one another as a connecting element, so that there is a current-conducting connection between the line regions 2.

In this embodiment, the current-conducting foil 4 is on the connection points 3 welded (dotted) and thus reliably connected mechanically and electrically with the line areas 2. Alternatively, the current-conducting foil 4 can also be fastened permanently to the connection points 3 in other ways.

The leadframe 1 comprises a series of tracks and areas that provide electrical connections between various positions in a module or module. The printed conductors of the stamped grid can be embedded in an insulating material. At locations where the interconnects are to be contacted, the insulation material is removed and components or connections can be electrically connected to the conductor track of the stamped grid 1.

Furthermore, an actuator 6 is provided which, when an ambient temperature exceeds a triggering temperature, moves a plunger 7 in the direction of the current-conducting foil 4. The punch 7 has at a free end a cutting edge 8 which slides along a cutting edge 9 of a cutting element and thereby performs a cutting. Between the cutting edge 9 and the cutting edge 8 is in the untripped state of the thermal fuse, the current-conducting film. 4

If the punch 7 is pressed upward when the thermal fuse is activated by activating the actuator 6, the current-conducting foil 4 between the cutting edge 8 and the cutting edge 9 is completely cut to interrupt the flow of current through the foil 4. The current-conducting foil 4 facing the end of the punch 7 has a bevel 11, which presses on a further movement of the punch 7 along the cutting edge 9, a portion of the current-conducting film of a further section at the cutting position. The punch 7 is preferably formed of a non-conductive material, so that after cutting through the current-conducting foil 4 can be reliably ensured that no electrical connection between the Lei 2 areas of the punching plate 1 consists. Furthermore, the material of the punch 7 should be selected so that the cutting edge 8 retains its sharpness throughout the life of the thermal fuse, such as ceramic.

The actuator 6 is preferably configured to move the plunger 7 without using electrical energy. Thus, the triggering of the thermal fuse is not dependent on the availability of a power supply.

In order to define the position of the actuator 6 with respect to the connecting element on the stamped grid 1, the actuator 6 is arranged on a carrier element 12 which is connected to the stamping plate 1 in a defined manner. Thereby, the alignment of the punch 7 of the actuator 6 in the direction of the current-conducting film 4 can be ensured. The support member 12 is preferably highly thermally conductive, e.g. formed of a metal to supply the ambient heat to the actuator 6.

2, a further embodiment of a thermal fuse is shown schematically. Like reference numerals designate like elements or elements of similar function.

The thermal fuse of FIG. 2 comprises a punching plate 1 with two line regions 2, which are connected to one another via a current-conducting film 4 as a connecting element. The current-conducting film 4 is welded via a first connection point 3 to a first of the line regions 2 or otherwise permanently and reliably electrically connected to the

Line area 2 connected. At a second connection point 3 of a second of the line regions 2, another end of the current-conducting film 4 is also electrically connected. However, the electrical contact between the current-conducting film 4 and the second connection point 3 is designed such that the connection between the current-conducting film 4 and the second line region 2 already due to an ambient temperature is released when the actuator 6 triggers.

The actuator 6 has no cutting in this embodiment. The free end of the punch 7 of the actuator 6 may be arbitrarily shaped. The punch 7, which moves in the event of tripping in the direction of the current-conducting film 4, then the current-conducting film 4 in a simple manner with little effort so lift that the other end of the current-conducting film 4 from the second connection point 3 of second line region 2 dissolves and thus interrupts the flow of current. Preferably, also in the second embodiment, the punch is not formed conductive; However, it can also be designed to be conductive, since the interruption of the current flow takes place in the region of the second connection point 3.

The electrically conductive connection between the second connection point and the current-conducting film 4 may be formed by a solder or with another conductive material. Exceeds the ambient temperature, the melting temperature of the solder or the other conductive material, the electrically conductive connection is initially maintained until at a further rise in ambient temperature causes the actuator 6 and due to the molten state of the solder, the current-conducting film without much effort of the can lift the second connection point 3.

Alternatively, both connection points 3 can also be connected to the current-conducting foil 4 by welding or another permanent connection. In this case, the force applied by the plunger 7 in the case of triggering must be so great as to tear the current-conducting foil 4 apart in order to interrupt the flow of current. In order to facilitate the severing of the current-conducting foil 4, the current-conducting foil may have a constriction, a perforation or an area of reduced thickness, at least in the area of impact of the punch 7, in order to create a predetermined breaking point, when the actuator 6 triggers. Furthermore, the current-conducting film 4 may be biased between the connection points 3, so that a separation is facilitated when the free end of the punch 7, the current-conducting film 4 strikes.

In Fig. 3, an example of an actuator 6 is shown in a cross-sectional view, as it can be used in the first and in the second embodiment. The actuator 6 comprises a cylindrical punch 7, which is provided with a stop element 15, which is located in the interior of an actuator housing 16 of the actuator 6. The stop element 15 has a preferably circumferential abutment surface 17, which is held by a fusible material 18 in the form of a fusible body of a cover plate 19, which serves as a further abutment surface 19 and through which the punch 7 protrudes, spaced. The stop element 15 is biased by a spring 19 which is arranged between the actuator housing 16 and an inner surface of a recess in the stop element 15. The spring element 19 thereby causes a spring force of the abutment surface 17 in the direction of the further cover plate 19, between which the fusible element 18 is arranged.

A triggering of this actuator occurs when the temperature has reached or exceeded a melting temperature at which the fusible material 18 melts and exits through an opening 21 between the cover plate 19 and the punch 7 from the actuator. Then, the stopper member 15 moves with the punch 7 in the direction of the force of the spring member 19 and the punch 7 is moved out of the actuator. Instead of such an actuator, other actuators may be provided which trigger when exceeding a certain ambient temperature and thereby perform a movement of an element which is used for a passage of a current-conducting connection, such as a translational movement of the punch 7, as in the Embodiments of FIGS. 1 and 2 is shown. FIG. 4 a shows a thermal fuse according to a third embodiment of the invention. Between the connection points 3 on the line regions 2 of the punching plate 1, a rigid connecting element 25 is applied, which is electrically conductive and electrically connected to the connection points 3 via a conductive, melting at a certain temperature material 26, such as a solder. The melting point of the material 26 is preferably below the trigger temperature of the actuator 6. The actuator 6 is designed, for example, as a primer in which, for example, two materials 27, 28 which react with one another can be separated from one another by a fusible partition 29. Alternatively, it is also possible to provide beads which contain one of the materials and an envelope of the fusible material of the

Have partition. When the trigger temperature is exceeded, the cladding melts and the two materials reacting with each other come into contact.

According to a further alternative, an ignitable material may be provided therein which ignites at a corresponding trip temperature, wherein an exothermic reaction takes place, which causes a corresponding change in volume. Preferably, the ignition material is selected to react in an exothermic reaction that accelerates itself.

As shown in FIG. 4b, as soon as the triggering temperature has been reached or exceeded, the dividing wall 29 melts and causes the two mutually reacting materials 27, 28 to come into contact and react with one another. The reaction causes a volume expansion in the direction of the connecting element 25, which is then lifted or displaced from the connection points 3, on which the already molten material 26 is located, and thereby interrupts the conductive connection between the line regions 2, as shown in FIG 4c, which shows the trigger case, is shown. Further embodiments are possible, which use as a bimetallic actuator actuator or a memory metal actuator as a triggering element.

Also, an actuator may include a biased spring element that is biased by a fuse element. Upon reaching the release temperature, the melting element melts and the spring element gives way and interrupts the foie 4 or generally the flat conductor.

In all embodiments, care must be taken that the corresponding actuator does not contain flammable materials.

In all embodiments, the connecting element 4, 25 designed so that at the maximum current for which the thermal fuse is designed, no appreciable increase in temperature of the connecting element occurs, i. the electrical resistance or the cross section is chosen so that the maximum current can be well supported by the connecting element. The triggering of the thermal fuse should only be done mechanically by the activation of the actuator and be irreversible, i. Under no circumstances should the opened fuse become conductive again.

Claims

claims

1. thermal fuse, in particular for use in an electrical module in the automotive sector, comprising: - a connecting element (4, 25) which is electrically and mechanically connected to a plurality of connection points to provide a permanent, electrically conductive connection via this; an actuator (6) formed separately from the connecting element (4, 25), which triggers without receiving electrical energy when an ambient temperature reaches a triggering temperature, and thereby the electrical connection formed by the connecting element (4, 25) to mechanical Way interrupts.

2. Thermal fuse according to claim 1, wherein the actuator (6) with a punch (7) is provided which is movable in a triggering case in the direction of the connecting element (4, 25), thereby to solve the electrical connection.

3. Thermal fuse according to claim 1 or 2, wherein the actuator (6) with a cutting mechanism (8, 9) is formed to NEN durchzutren- NEN when triggering the connecting element (4).

4. Thermal fuse according to one of claims 1 to 3, wherein the connecting element (4) is designed as a current-conducting flat conductor, in particular as a foil or sheet.

5. thermal fuse according to claim 4, wherein the flat conductor (4) is provided with a Sollauftrennstelle.

6. Thermal fuse according to one of claims 1 to 5, wherein the connection points are arranged on line areas of a punched grid (1).

7. thermal fuse according to one of claims 1 to 6, wherein the actuator (6) is arranged on a carrier element (12) that is connected to the stamped grid (1) to a Alignment of the actuator (6) with respect to the connecting element (4, 25) set.

8. A thermal fuse according to any one of claims 1 to 7, wherein the actuator (6) comprises one or more mutually reactive materials (27, 28) which are separated by a fusible partition (29), wherein the melting temperature of the partition (29) the triggering temperature corresponds, wherein the actuator (6) is arranged on the connecting element (25), that in the case of triggering a volume change due to the mutually reactive materials interrupts the electrical connection formed by the connecting element (25).

9. thermal fuse according to claim 8, wherein the connecting element (25) at the connection points (3) by a fusible material at a melting temperature (26) is connected, wherein the melting temperature of the fusible material is equal to or less than the triggering temperature.

10. A thermal fuse according to any one of claims 1 to 7, wherein the connecting element (4, 25) with each of the connection points (3) either fixedly connected or connected by means of a fusible material at a melting temperature, wherein the melting temperature of the fusible material is equal to or less than the trip temperature.