GB2489101A

GB2489101A - Pyrotechnically actuated fuse for a motor vehicle

Info

Publication number: GB2489101A
Application number: GB1204485.5A
Authority: GB
Inventors: Ja Rgen Tautz
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2011-03-18
Filing date: 2012-03-14
Publication date: 2012-09-19
Also published as: DE102011014343A1; GB201204485D0

Abstract

A safety device for a voltage supply of a motor vehicle comprises a conductor 2 having a breaking point 22 which is cut through by triggering an explosive charge (fig 1, 32) of a pyrotechnic safety element 3. A fuse of the conductor element is cut through by melting when the current is exceeded. The breaking point 22 and the fuse 23 can be connected in series (fig 1) or the fuse 23 can also form the breaking point 22. The pyrotechnic safety element and the fuse can be integrated in a housing that has external connections 61,62 to trigger the explosion and a controller 11 to receive and evaluate plural signals to trigger the drive charge. The conductor 2 can be stamped copper and between a vehicle battery terminal and plural consumers. A second safety device having a fuse but no pyrotechnic element can be between a terminal of the battery and a consumer. The vehicle can have a sensor that detects an accident and outputs a signal causing the drive charge to explode.

Description

SAFETY DEVICE FOR A VOLTAGE SUPPLY OF A MOTOR VEHICLE

DESCRIPTION

The application relates to a safety device for a voltage supply of a motor vehicle. In mo-tor vehicles safety devices are used to protect cable from excessively high currents. If a short circuit occurs in a vehicle, for example, due to an accident, a fuse usually ensures that the circuit is interrupted. This interruption is accomplished by an electrical conduc-tor in the fuse melting as a result of the high short circuit current through this electrical conductor.

DE 694 14 798 T2 discloses a safety cutoff device with the aid of a combination of a fuse and a mechanical switch.

DE 100 49 071 Al discloses a safety device in which both a pyrotechnic safety device and an overcurrent protection are provided in one housing. The pyrotechnic safety de- vice contains a drive charge which, when it explodes, cuts through a conductor ele-ment. At the same time, a constriction is provided in the current-carrying path which is heated when the current exceeds a predetermined switching threshold. The pyrotech-nic safety device is triggered by this heating. In this case, however, the time between the heating in the constriction until the triggering of the drive charge should be taken into account.

It is the object of the application to provide a safety device for a circuit in a motor vehi-cle in which the interruption of the circuit takes place rapidly in critical situations.

This object is solved by the subject matter of the independent claims. Advantageous embodiments are obtained from the particular subclaims.

A safety device is provided for a circuit of a motor vehicle where the safety device comprises a conductor element with a predetermined breaking point. In addition, the safety device contains a pyrotechnic safety element with a drive charge which, when triggered, cuts through the predetermined breaking point of the conductor element. A fuse which, when exceeding a predetermined temperature, cuts through the conductor element by melting is also provided in the safety device.

Two safety concepts are combined with the safety device. On the one hand, cables which are damaged by wear or mechanical impulses are protected by the fuse when the current increases severely. On the other hand, the pyrotechnical safety element can be actively triggered, which is appropriate for example in the case of an accident.

Particularly in the first case in which the cable is defective because, for example, the insulation of a cable is frayed, causing a short circuit, the fuse is activated rapidly.

This means that the increase in the current directly causes a cutting through of the conductor element. This direct triggering of the conductor element is safe compared with the cutting through of the conductor element by the pyrotechnic safety element since the triggering of the pyrotechnic safety element is more complex than the fuse.

The triggering of the pyrotechnic safety element can be accomplished in a controlled fashion for this, Ft is thereby possible to achieve a plurality of conditions in order, for example, to detect an accident. A pyrotechnic safety element is triggered or not de-pending on a combination of these conditions.

In one embodiment the predetermined breaking points and the fuse are connected in series. As a result of the separate arrangement of the predetermined breaking point and the switch fuse, these can be dimensioned independently of one another and therefore precisely for their respective intended purpose.

If, on the other hand, the fuse also forms the predetermined breaking point, a particu-larly compact structure of the safety device is possible which saves space and weight in the vehicle. -3-.

If the safety device has a housing to which electrical external connections are attached by which means the explosive charge of the pyrotechnic safety element can be trig- gered from outside the housing, it is possible to be able to trigger the pyrotechnic safe-ty element by means of a simple cable connection to the safety device.

The cable can thereby be, for example, plugged, soldered or clamped to the external connection according to the type of connection.

Preferably the pyrotechnic safety element and the fuse are integrated in a housing. As a result, only one component is required which is inserted in the current path to be se-cured.

In one embodiment a control device is provided for triggering the drive charge of the pyrotechnic safety element, where the control device is adapted to receive and evalu-ate a p(urality of input signals. With the aid of a plurality of input signals, it is thereby determined in the control device whether the drive charge should be triggered. For ex- ample, a plurality of sensors can be used to detect an accident, where it can be deter- mined in the control device which and how many of the sensors must display the acci-dent in order to actually trigger the drive charge of the pyrotechnic safety device.

ln one embodiment the control device is provided in the same housing as the pyro-technic safety element. it is therefore not necessary to provide its own housing for the control device, which overall simplifies the assembly in the vehicle.

In a further embodiment, the conductor element contains a stamped part made of cop-per in which in particular the predetermined breaking point is formed. Copper is known for its very good conductivity.

A vehicle having a safety device presented hereinbefore is also provided. In this case, the safety device is switched in the path between a negafive terminal of the vehicle bat- tery on one hand and a plurality of first consumers on the other hand. The safety de-vice thus serves as a safety device for a plurality of first consumers which are switched -4-.

off in their entirety if a short circuit or another process occurs which necessitates an ignition of the drive charge of the pyrotechnic safety element.

The conductor element can be configured as one part but it can also consist of several parts.

Preferably a safety device which contains a fuse but no pyrotechnic element is provid- ed in the path between the terminal of the vehicle battery and at least one second con-sumer. Thus, those consumers which should not be separated from their power supply in the event of an accident can be switched as second consumers. This can be, for ex-ample, the lighting apparatus of the vehicle and the automatic door closing system which should still be energised after the accident so that the vehicle can still be identi-fied from outside and the vehicle occupants can climb out.

Attempts are made to ensure that as many consumers as possible belong to the first consumers. The power supply is thus interrupted for as many consumers as possible by the pyrotechnic safety element. In the case of an accident there is an increased risk that cables will be damaged and thus cause short circuits. Cables leading to the first consumers can, however, after triggering of the pyrotechnic element, no longer cause short circuits. Merely those cables leading to the voltage supply connections of the se- cond consumers are at risk. However, these must still be supplied with electrical ener- gy so that the vehicle occupants can climb out and so that the vehicle is still illuminat-ed.

A method for triggering a safety device presented hereinbefore is also provided. In this case, the vehicle has a sensor for detecting an accident. The sensor outputs a signal after detecting an accident, which causes the drive charge of the pyrotechnic safety element to explode.

A circuit breaker in the form of the pyrotechnic safety element is thus combined with a fuse. The separation is started with the fuse as soon as a short circuit has occurred, thereby preventing the predetermined current limits being exceeded. An external acti-vation is not required for this.

The pyrotechnic circuit breaker is started by external activation. If, for example, an air- bag control module detects an accident, a signal is sent to the pyrotechnic safety ele- ment so that the conductor element is interrupted immediately. The principle of the cir- cult breaker is based on a piece of metal that is, for example, cut through by a non-conducting piston where the piston is driven by the pyrotechnic element.

The subject matter of the application is now explained with reference to an exemplary embodiment. In the figures: Figure 1 shows a first embodiment of a safety device with a fuse and a predeter-mined breaking point which are connected in series; Figure 2 shows the safety device from Figure 1 when the fuse is triggered; Figure 3 shows the safety device from Figure 1 after triggering a pyrotechnic safety element; Figure 4 shows a second embodiment of a safety device; Figure 5 shows the safety device from Figure 4 when the fuse is triggered; Figure 6 shows the safety device from Figure 4 when a pyrotechnic safety ele-ment is triggered; Figure 7 shows the housing of a safety device; Figure 8 shows a vehicle with a safety device integrated in the voltage supply.

Figure 1 shows a first embodiment of a safety device with a series-connected fuse and a predetermined breaking point for insertion in a circuit of a motor vehicle. The safety device I contains a housing 4 and a conductor element 2, which runs partially in the housing 4 and projects in each case to the right and left from the housing. A connecting region 8 is provided on the left side and a connecting region 9 is provided on the right side for connection of external cables. The conductor element 2 tapers inside the hous-ing 4. A further tapering of the conductor element 2 is provided in the area of a fuse 23.

In addition, a predetermined breaking point 22 is provided in the conductor element 2.

The housing is filled with an elastomer 5. Located in this elastomer 5 is a cavity 10 which comprises a pyrotechnic safety element 3 and a sealing plate 70. A control de- vice II is additionally provided inside the elastomer, said control device having an in-put F and an output A. The input E is electrically connected to an external connection 6 located on the outer side of the housing 4. This external connection 6 is adapted for connection to a signal line 7. The control device is connected with its output A to an input of the pyrotechnic safety element 3. The pyrotechnic safety element comprises a drive charge 32 and a trigger circuit 33.

The safety device I is used for connection into a current path of a voltage supply of a motor vehicle. To this end, a cable leading to the negative terminal of a vehicle battery is connected to one of the connecting regions 8 and 9 whilst a cable leading to voltage supply connections of a plurality of first consumers is connected to the other one of the connecting regions 8 and 9. This results in a current flow through the conductor ele-ment 2 from the vehicle battery to the first consumers. If, for example, the cable leading to the first consumers is defective because the insulation is damaged and at the dam-aged location a short circuit leads to the positive terminal of the battery, the current I through the conductor element 2 is increased.

The fuse 23 is configured so that when a predetermined threshold is exceeded, for ex-ample, 60 A, the fuse 23 melts, whereby the conductor element 2 is broken through. It should be noted that the conductor element 2 can consist of one part. Frequently, how-ever, a different material from that for the conductor element 2 is used for the fuse 23 so that the conductor element 2 consists of several parts. At an increased current the conductor element 2 is directly interrupted since no evaluation circuit is required.

If, on the other hand, an accident is detected, this is detected by an airbag sensor which applies a corresponding signal to the signal line 7. The signal is received via the signal line 7 and the external connection 6 from the control device 11 at the input E of the control device 11. The control device 11 outputs a signal at its output A, which leads to ignition of the trigger circuit 33 causing the drive charge 32 to explode. The sealing plate 70 is thereby pressed downwards, breaking the predetermined breaking point 22. The current 1 can therefore no longer flow through the conductor element 2.

The cavity 10 is used to receive the fragments of the predetermined breaking point 22 * and the sealing plate 70. The elastomer 5 is compressive so that it is compressed dur-ing the explosion of the drive charge 32. This prevents the housing of the safety device -7-.

1 from being damaged overall and the drive charge 32 causing damage outside the housing 4.

Figure 2 shows the safety device from Figure 1 at a time after the conductor element 2 has been cut through by the fuse 23. The fuse 23 is heated when the current through the fuse 23 exceeds 60 A. This heating leads to a melting of the leads in the fuse. The leads become deformed and bring about an interruption of the current J through the conductor element.

Figure 3 shows the safety device 1 from Figure 1 after triggering of the pyrotechnic safety element. It can be seen that the conductor element 2 is broken through at the position of the former predetermined breaking point. Fragments 100 of the conductor element 2, the sealing plate and the pyrotechnic safety element are located in the lower region 120 of the cavity 10.

Figure 4 shows a second embodiment of the safety device 1. In this case, the prede-termined breaking points 22 and the fuse 23 are integrated with one another at one point. This means that that region of the conductor element 2 that forms the fuse 23 is also a predetermined breaking point 22 which is cut through by the sealing plate 70 in the event of the pyrotechnic safety element being triggered.

In a vehicle in which there are several airbags and airbag control modules, each of the modules outputs a signal which indicates whether it has detected an accident. The dif-ferent signals can be received by the control device. In this embodiment according to Figure 4, the output signals from two airbag control modules are output via signal lines 71 and 72. The safety device I from Figure 4 has two external connections 61 and 62, where the control device 11 is connected at a first input El to the external connection 61 and at a second input E2 to the external connection 62. The signal line 71 is con-nected to the external connection 61 and the signal line 72 is connected to the external connection 62.

In the control device lithe signals are received at the inputs El and E2 and according to the input signals it is decided whether the pyrotechnic safety device should be trig- gered. For example, the pyrotechnic safety device should only be triggered if both air-bag control modules have detected an accident. It is understood that by modification of the safety device 1, a plurality of other signals from various sensors can be taken into account when making the decision.

Figure 5 shows the safety device I from Figure 4 after the fuse 23 has been triggered.

The current 1 through the conductor element 2 was greater than 60 A so that the con- ductor element 2 is melted in the region of the fuse 23, thereby interrupting the conduc-tor element 2.

Figure 6 shows the safety device 1 according to Figure 4 after triggering the pyrotech-nic safety element. The conductor element 2 is interrupted in the lower region 120 of the predetermined breaking point 22. Fragments 100 of the sealing plate, the conductor element 2 and the pyrotechnic safety element are located in the lower region 120 of the cavity 10.

Figure 7 shows a safety device in a plan view obliquely from above. The safety device I can be configured according to the first exemplary embodiment according to Figure 1 or according to the second exemplary embodiment according to Figure 4. The connect-ing region 8 projects to the left and the connecting region 9 projects to the right. The external connection 6 can be identified on the front part of the housing 4. This can be configured as an electrical external contact, it can be soldered onto a cable or config-ured as a plug. The connecting regions 8 and 9 each have openings 30 which each serve to receive a screw connection.

Figure 8 shows a motor vehicle 40 with a safety device 1 which is provided in the path between the negative terminal of a vehicle battery and a plurality of voltage supply connections from first consumers 42. A second safety device 50 which merely contains a fuse is provided between the negative terminal of a vehicle battery 41 and a supply connection of a second consumer 43. The second supply connections of the first con-sumers 42 and the second consumers 43 are each connected to the positive terminal of the vehicle battery 41. The second consumers 43 comprise safety-critical consumers which must still be supplied with electrical energy in the case of an accident. These are, for example, automatic door closing systems and lighting devices of the motor ve- hicle. The first consumers are consumers which are switched off in the case of an acci- dent so that no current-carrying conductors cause further damage. These are consum-ers such as engine control, driver assistance systems and infotainment devices. Figure B additionally shows a first airbag control module 200 and a second airbag control module 201 which are connected with signal outputs to the signal lines 71 or 72.

The safety device is particularly suitable for vehicles in which the main supply line is guided below the vehicle from the battery to the consumers. The main supply line should be interrupted if mechanical damage occurs. At the same time, it should be en-sured that in the event of an accident sufficient electrical energy is available to unlock the doors. In addition, alarm signals should be transmitted electrically and the lighting in the vehicle and outside the vehicle should still be supplied.

Although at least one exemplary embodiment was shown in the preceding description, various changes and modifications can be made. The said embodiments are merely examples and not provided to restrict the range of validity, the applicability or the con-figuration in any way. On the contrary, the preceding description provides the person skilled in the art with a plan for implementing at least one exemplary embodiment, where numerous changes in the function and the arrangement of elements described in one exemplary embodiment can be made without departing from the scope of pro-tection of the appended claims and their legal equivalents.

-10 -Reference list 1 Safety device 2 Conductor element 3 Pyrotechnic safety element 4 Housing Elastomer 6 External connection 7 Signal line 8 Connecting region 9 Connecting region Cavity 11 Control device 22 Predetermined breaking point 23 Fuse Opening 32 Drive charge 33 Trigger circuit Motor vehicle 41 Vehicle battery 42 First consumer 43 Second consumer Safety device 61 External connection 62 External connection Sealing plate 71 Signal line 72 Signal line Fragments Lower region -1_i -First airbag control module 201 Second airbag control module

Claims

-12 -QLAIMS1. Safety device (1) for a voltage supply of a motor vehicle comprising: -a conductor element (2) that has a predetermined breaking point (22), -a pyrotechnic safety element (3) with a drive charge (32), which when trig- gered, cuts through the predetermined breaking point (22) of the conductor el-ement, -a fuse (23) in the conductor element (2), which cuts through the conductor element by melting when a predetermined current is exceeded.
2. The safety device according to claim 1, wherein the predetermined breaking point (22) and the fuse (23) are connected in series.
3. The safety device according to claim 1, where the fuse (23) also forms the predetermined breaking point (22).
4. The safety device according to any one of claims I to 3, wherein the safety device (I) comprises a housing (4), wherein electrical external connections are attached to the housing (4) by which means the explosive charge of the pyrotechnic safety element (3) can be triggered from outside the housing (4).
5. The safety device according to any one of claims I to 4, wherein the pyro-technic safety element (3) and the fuse (23) are integrated in a housing (4).
6. The safety device according to any one of claims 1 to 5, wherein a control de-vice (11) is provided for triggering the drive charge (32) of the pyrotechnic safety element (3), wherein the control device (Ii) is adapted to receive and evaluate a plurality of input signals.
7. The safety device according to claim 6, wherein the control device (11) is pro-vided in the same housing (4) as the pyrotechnic safety element (3).
-13 - B. The safety device according to any one of claims 1 to 6, wherein the conduc-tor element (2) contains a stamped part made of copper.
9. Vehicle having a safety device according to any one of claims I to 8, wherein the safety device (1) is switched in the path between a terminal (-) of the vehi- cle battery (41) on one hand and a plurality of first consumers (42) on the oth-er hand.
10. The vehicie according to claim 9, wherein a second safety device (50) which contains a fuse (23) but no pyrotechnic element is provided in the path be- tween the terminal of the vehicle battery (41) and at least one second con-sumer (43).
11. Method for triggering a safety device according to any one of claims I to 9 in a vehicle, where the vehicle has a sensor for detecting an accident, wherein the sensor outputs a signal after detecting an accident, which causes the drive charge (32) of the pyrotechnic safety element (3) to explode.