DE102013016093B4 - Method for controlling a pyro fuse in a motor vehicle and motor vehicle - Google Patents

Abstract

Method for controlling a pyro fuse (9) provided in an electrical line (4) connecting the generator (6) and the starter (5) of a motor vehicle (1) to a battery (3) of the motor vehicle (1), which pyro fuse (9) is provided when a An accident signal indicating an accident in the motor vehicle (1) is actuated to disconnect the line (4) and is arranged in such a way that a part of an on-board network (2) of the motor vehicle (1) that is not connected to the battery (3) via the line (4) Triggering of the pyrofuse (9) can still be supplied from the battery (3), characterized in that the pyrofuse (9) for disconnecting the line (4) is also faulty when there is an overvoltage signal indicating an overvoltage at the generator (6) and a faulty one permanently closed switching device (14,15) for energizing the starter (5) indicating switch signal is controlled.

Description

The invention relates to a method for controlling a pyrofuse provided in an electric line connecting the generator and the starter of a motor vehicle to a battery of the motor vehicle, which is controlled to disconnect the line when an accident signal indicating an accident of the motor vehicle is present and is arranged in such a way that a part of an on-board network of the motor vehicle that is not connected to the battery via the line can continue to be supplied from the battery when the pyro fuse is triggered.

Pyrofuses are already known in principle in the prior art. These use a pyrotechnic material mixture which, when ignited, mechanically and sustainably interrupts an associated line. Pyrofuses are known, for example, which accelerate a mechanical interrupting element in the direction of the line when it is ignited and thus interrupt it by force. For example, a piston closing an ignition chamber in the non-triggered state can be accelerated by the ignition.

Pyrotechnic fuses (pyro fuses) are always used when conventional fuses are not sufficient to achieve a safe interruption of the electrical line. An example of this is an electric line in a motor vehicle, which connects a battery there to the generator there and the starter there. During the starting process in particular, this line carries currents that can have a current strength of up to 1,000 amperes. A conventional fuse is therefore not suitable for adequately protecting and destroying the line.

According to the usual designation, this is a terminal 30 line.

The purpose of the pyro fuses in series production today is to prevent fires in the event of accidents, particularly in the event of a motor vehicle collision. For this reason, the pyro fuse in a motor vehicle in the known prior art is triggered on the basis of an accident signal, in particular a collision signal, which is determined by evaluating suitable sensor data, which can come from collision sensors, for example. Due to the irreversible triggering of the pyro fuse, the line between the starter and the battery is safely interrupted and the risk of fire in the vehicle is significantly reduced.

DE 197 19 919 A1 discloses an arrangement for the protection of electrical devices, which specifically concerns protection against consumers from damage to a battery caused by polarity reversal. It is proposed to connect a limiting element in parallel with the vehicle electrical system and to disconnect the electrical connection to the vehicle electrical system by a switching isolating element, which can be a thermally activatable explosive switching element, if there is a case of polarity reversal.

DE 10 2007 061 112 A1 describes a sensor arrangement and a diagnostic method for detecting the status of a battery and/or electrical consumers in a motor vehicle. In the process, the electrical state variables current, voltage and temperature should be recorded in the vicinity of the pole terminals of the battery, cf. already summary, in order to also diagnose defects in the generator and the starter. The only measure mentioned is early warning to the driver of the motor vehicle.

In DE 10 2004 031 306 A1 a motor vehicle energy management with additional functionality starter diagnosis is described. It is proposed to integrate the diagnosis of a starter of an internal combustion engine into an energy management system. In this way, starter problems can be detected early and can be read out so that preventive maintenance measures are possible. It is also described that if the cut-off current is too high, an error flag can be set, which indicates sticking relay contacts. Furthermore, the battery disconnect switch can be actuated to separate the starter from the vehicle electrical system, although the switch is also provided here in a line that connects the battery to all consumers, so that these sticky relay contacts would lead to the entire vehicle electrical system is switched off.

DE 10 2011 103 834 A1 relates to a switching system for motor vehicle power conductors, with both a switching device and a disconnecting device for irreversibly disconnecting the current path being provided in the switching system. In the event of an accident or a comparable safety-relevant operating state of the motor vehicle, the disconnecting device can ensure a safe disconnection of the current path in the relevant motor vehicle power conductor. The separating means can have a pyrotechnic auxiliary drive. Specifically, it is about the connection of an energy supply device with an energy consumer, for which an electric drive or auxiliary motor for driving the motor vehicle in hybrid or electric vehicles is mentioned as the only example.

DE 43 26 527 A1 describes a safety device in motor vehicles for shutting off the electrical current delivered by a motor vehicle battery. The motor vehicle battery is also to be completely disconnected from the vehicle electrical system there, with the problem that safety-relevant systems can then no longer be triggered. It is therefore proposed to provide an additional condition for disconnecting the motor vehicle battery from the vehicle electrical system, namely to check whether a short circuit actually occurs between the battery supply lines.

Out of US 2008/0 151 454 A1 a safety switch for a battery is known, which enables a controllable separation of the battery, ie a reversible separation.

DE 103 52 266 A1 relates to an electrical safety device for a motor vehicle, with both a first safety element for the engine starting device and a further safety element for at least one electrical consumer of the motor vehicle being positively fastened and integrated in one component directly on a pole terminal of the battery. A high-current fuse element designed for high current intensities can be provided as the first fuse element for disconnecting the starter line and thus protecting the motor vehicle from fire damage as a result of overvoltages, in particular a pyrotechnic disconnect element operated by means of a propellant charge. This is triggered by a control signal from the motor vehicle's airbag control unit, which indicates that the airbag has been triggered. The additional security element can relate in particular to safety-relevant electrical loads in the motor vehicle and is in particular designed as a safety fuse. The integration of several safety elements in one component results in a compact and cost-effective electrical safety device for the electrical consumers of the motor vehicle connected to the starter cable on the one hand and for other electrical consumers of the motor vehicle on the other hand.

Proceeding from this, the invention is based on the object of expediently expanding the possible uses of such a pyro fuse in order to increase the safety of the motor vehicle.

To solve this problem, in a method of the type mentioned at the outset, the invention provides that the pyro fuse for disconnecting the line is also activated in the presence of an overvoltage signal indicating an overvoltage at the generator and a switch signal indicating a faulty, permanently closed switching device for energizing the starter.

According to the invention, it was recognized that an irreversible severing of the line between the starter and the generator and the battery can also be expedient in the case of other effects in the motor vehicle in order to increase the safety of the motor vehicle. The first of these cases is an overvoltage of the alternator, which can lead to an overvoltage in the on-board network. This can lead to system failures and have critical consequences in particular when new battery types other than a lead battery are used in the motor vehicle. In particular, the use of lithium batteries has recently been widely proposed, the various variants of which are extremely sensitive to overvoltage, especially when compared to a conventional lead-acid battery. For example, a lithium iron phosphate battery has a maximum permissible charging voltage of 14.7 volts, above which the lithium battery can be damaged or even destroyed, resulting in a total failure of the vehicle electrical system and possibly even further damage to the motor vehicle can bring. It is therefore proposed according to the invention to also trigger the pyro fuse when an overvoltage signal from the generator indicates an overvoltage, so that the line to the generator is destroyed and the overvoltage can no longer reach the rest of the vehicle electrical system.

In this case, however, the motor vehicle can still be supplied with power from the battery, so that safe parking of the motor vehicle is still ensured. The fault on the generator can be eliminated in a workshop, the line can be repaired and the pyro fuse can be replaced. The damage to the motor vehicle is therefore kept as small as possible.

An overvoltage on the generator can occur if a control device of the generator fails, generally speaking "runs away". More voltage is then made available from the generator in the vehicle electrical system after limitation no longer occurs.

The second case in which the present invention can increase safety in the motor vehicle is the undesired permanent energization of the starter, and therefore in particular also of the starter motor of the starter. There are usually two switching devices, implemented in particular as relays, with regard to the starter. A first switching device receives the switched plus of the ignition starter switch (terminal 15) as a control signal and is closed when a start signal (terminal 50) indicating desired operation of the starter is given will. The ignition signal present at the second switching device in turn closes it, so that the operating voltage of the battery can reach the starter motor. However, these switching devices can have a malfunction that ensures that the switching device is closed despite the absence of signals.

When using relays as switching devices, for example, it is possible for an arc to form in the relay when it bounces off (or generally referred to as “bouncing”), which can weld the relay, so to speak, and thus ensure a permanent connection. Another reason why a permanent electrical connection can remain in a relay due to overheating is overheating of the contact resistance. This is often referred to as "sticking" of the relay.

Since this can become safety-critical, for example with regard to self-acceleration of the motor vehicle or a possible vehicle fire, it is known in the prior art to use and monitor two series-connected switching devices, ie in particular two relays.

According to the invention, it is now proposed to also use a switch signal indicating such a permanent undesired energization of the starter, in particular the starter motor, in order to trigger the pyro fuse and to cut through the line. If the pyro fuse is therefore used as an additional switch-off element in the event of a defect in a switching device, one of the redundant switching devices provided in the prior art can be dispensed with, so that cost savings are achieved.

In this way, the pyro fuse that is present anyway is appropriately actuated even in the case of other error states in the motor vehicle, in order to increase overall safety. Ideally, no additional components are required for this, in particular when corresponding means for determining the overvoltage signal and/or the switch signal are already provided.

As has already been noted, the method according to the invention can be used particularly advantageously, in particular with regard to the overvoltage signal, if the battery is a lithium battery. However, it should be pointed out that a conventional lead-acid battery may clamp the voltage and even limit it to approx. 18 volts with a normal vehicle electrical system voltage of 12 volts, nevertheless damage and faster aging of the lead-acid battery occurs there. When using a lithium battery, an overvoltage on the alternator is far more critical for the reasons already outlined.

To determine the overvoltage signal, a voltage measurement can be carried out on the generator and evaluated. In this case, a conventional voltage device can be used, as is usually provided on the generator anyway.

Specifically, it can be provided that the overvoltage signal is given for a predetermined period of time when a threshold value for the voltage at the generator is exceeded and/or when there is an overvoltage at the generator that is in particular below the threshold value but above a defined overvoltage range of the battery . The two criteria mentioned here for generating an overvoltage signal are preferably both used, so that an overvoltage range ending in particular at the threshold value is given, in which different values for the overvoltage are assigned different predetermined time durations. Because it has been shown that even with lithium batteries, a brief overvoltage does not necessarily lead to damage or safety risks, so that lower overvoltages can be permitted for a predetermined period of time without destroying the cable. In this way, short-term voltage fluctuations or the like can be tolerated. However, there is usually an overvoltage, namely the threshold value, which is directly dangerous for the battery used, in particular a lithium battery. If this is reached, the pyro fuse should trigger immediately.

In an advantageous further embodiment of the present invention, a threshold value can be used which corresponds to the maximum permissible charging voltage of the battery or exceeds it by a predetermined amount. The maximum permissible charging voltage of the battery is expediently used as a threshold value in particular when there is no overvoltage range and a high level of safety is to be achieved in any case. If there is an overvoltage range for which predetermined periods of time are present, or if a greater tolerance is to be permitted, the threshold value should be set greater than the maximum permissible charging voltage, for example exceeding this by 5% to 20%. For example, in the case of an iron phosphate-lithium battery with a maximum permissible charging voltage of 14.7 volts, a threshold value of 15.5 volts or 16 volts can be set, even if an overvoltage range up to this threshold value is allowed.

Furthermore, it is preferred if each overvoltage lying in the overvoltage range is assigned a predetermined period of time using a characteristic curve or a look-up table, in particular a predetermined period of time that decreases as the overvoltage increases. Provision can thus be made, for example, for lower overvoltages to be present for a longer period of time before the overvoltage signal is given, but this time decreases the higher the overvoltage becomes. If the overvoltage range is defined as being limited by the maximum permissible charging voltage and the threshold value, the predetermined time period can reach the value zero according to a characteristic curve or a look-up table when the threshold value is reached.

To determine the switch signal, a voltage measurement can expediently be carried out within the starter, in particular on a starter motor of the starter, and the switch signal can be given if an operating voltage is present without a start signal indicating desired operation of the starter being present. Ultimately, a suitable voltage measuring device is used to check whether the operating voltage is present at the starter motor, but at the same time the signal for a desired starting process (terminal 50 signal) is not present. If this is the case, the switch signal is generated since it can be assumed that a switching device is incorrectly and permanently closed.

In a further development of the invention, it can be provided that a control unit assigned to the pyro-fuse is used to activate the pyro-fuse, to which the overvoltage signal and/or switch signal are supplied by at least one diagnostic control unit. A kind of master control unit is therefore provided for the pyro fuse, which takes over its control centrally.

In addition to the method, the present invention also relates to a motor vehicle, comprising an on-board electrical system with a battery, a starter, a generator and a line connecting the starter and the generator to the battery, which line can be interrupted by a pyro fuse controlled by at least one control unit, wherein the control unit is designed to carry out the method according to the invention. All explanations regarding the method according to the invention can be applied analogously to the motor vehicle according to the invention, with which the same advantages can therefore be achieved. There is also an expansion of the field of application of the pyro fuse, in that corresponding signals processed to trigger the pyro fuse, namely the overvoltage signal and/or the switch signal, are determined and used.

• 1 eine Prinzipskizze eines erfindungsgemäßen Kraftfahrzeugs,
• 2 eine konkrete Verschaltung bezüglich des Starters, und
• 3 eine Kennlinie für vorbestimmte Zeitdauern in einem Überspannungsbereich.

Further advantages and details of the present invention result from the exemplary embodiments described below and from the drawing. show:

• 1 a schematic diagram of a motor vehicle according to the invention,
• 2 a specific connection with regard to the starter, and
• 3 a characteristic for predetermined periods of time in an overvoltage range.

1 shows a schematic diagram of a motor vehicle 1 according to the invention. This has a 12 volt electrical system 2, which is fed by a battery 3, here a lithium battery. A starter 5 (also referred to as a starter) and a generator 6 are connected to the battery 3 via a line 4 . A further line 7 here only hints at further loads 8 connected to the battery 3 .

A pyro fuse 9 is provided in the line 4 and is designed to irreversibly interrupt the line 4 when a corresponding activation signal is received from a control unit 10 that is assigned to the pyro fuse 9 . For example, a mechanical element, for example a piston, can be accelerated in the direction of the line 4 and break through it by igniting a pyrotechnic material mixture.

The pyro fuse 9 is triggered when an accident signal indicating an accident, which can be determined, for example, from data from a number of sensors, in particular including collision sensors, is present. However, two further signals are also provided in the motor vehicle 1, which result in the pyro fuse 9 being triggered when they are supplied to the control unit 10.

These two additional signals relate to starter 5 and generator 6 and are determined by a diagnostic control unit 11 . For this purpose, a first voltage measuring device 12 measures the voltage at the starter motor of the starter 5, and a second voltage measuring device 13 measures the voltage at the generator 6.

The voltage in the starter 5, specifically at the starter motor, is evaluated together with a start signal (terminal 50 signal) indicating a desired operation of the starter 5 in order to determine a switch signal which indicates that the operating voltage is present at the starter 5 despite the absence of a start request , Therefore, at least one of the starter 5 associated switching device is permanently closed incorrectly, which with regard to 2 should be explained in more detail.

2 FIG. 1 shows the wiring with regard to the starter 5 in more detail, with the diagnosis control unit 11 also taking on the general activation of the starter 5 in the present case. The operation of the starter 5 is controlled via a first switching device 14 and a second switching device 15 . Both switching devices 14, 15 are designed as relays. The first switching device 14 forwards an ignition signal (“ignition on”), terminal 15, see feed 16, to the second switching device 15 when the switching device 14 is closed. If the diagnostic control unit 11 receives the start signal, supply 17, indicating the desired operation of the starter 5, the first switching device 14 is closed as long as it is present.

If the ignition signal is present at the second switching device 15 , this is closed again and the operating voltage is made available to the starter motor 18 by means of the line 4 .

If one of the two switching devices 14, 15 is permanently closed, the operating voltage is constantly present at the starter motor 18, regardless of the start signal, which is monitored by the voltage measuring device 12, which supplies its data to a diagnostic component 19 of the diagnostic control unit 11.

If it is determined there that an operating voltage is present at the starter motor 18 without a start signal (terminal 50) indicating the desired operation of the starter 5, a switch signal is generated and transmitted to the control unit 10 via a connection 20, which triggers the pyro fuse 9 to interrupt the line 4 controls.

The second in addition to the accident signal, which according to 2 Likewise, cf. arrow 21, which can be added to the control unit, the triggering signal provided for the pyro fuse 9 is an overvoltage signal indicating an overvoltage at the generator 6, which is determined in the diagnostic control unit 11 using the voltage measured by the voltage measuring device 13. There are two different criteria for triggering the pyro fuse 9, depending on how high the overvoltage is. First, an overvoltage range is specified, which ranges from a maximum allowable charging voltage of the battery 3 to a threshold value above the maximum allowable charging voltage. Within this overvoltage range, an overvoltage must be present for a predetermined period of time that depends on the value of the overvoltage in order to generate the overvoltage signal, after briefly exceeding the maximum permissible charging voltage does not necessarily lead to damage to the battery 3, which is designed as a lithium battery, or to a safety risk got to. Only when the threshold value for the voltage at the generator 6 is exceeded is the overvoltage signal output immediately and the pyro fuse 9 ignited.

When using an iron phosphate-lithium battery as battery 3, for example, in which the maximum permissible charging voltage for a 12-volt network can be 14.7 volts, the threshold value can be selected as 15.5 or 16 volts, for example.

In order to determine how long an overvoltage in the overvoltage range must be present in order to generate the overvoltage signal, a characteristic curve 25 is stored in diagnostic control unit 11, as shown in FIG 3 is shown. In 3 the voltage U at the generator 6 is plotted against the corresponding predetermined period of time Δt. As can be seen, the characteristic curve 25 is only defined for the overvoltage range 22 which is limited by the maximum permissible charging voltage 23 and the threshold value 24 . At the threshold value 24, the characteristic curve reaches a value of zero for the predetermined period of time, so that there is a constant transition here. However, the maximum permissible charging voltage 23 may also be present for a longer predetermined period of time, for example 20 seconds. The progression between these values can be linear, for example.

If there is an overvoltage in the overvoltage range 22 , it is therefore checked whether this overvoltage is maintained for the corresponding predetermined period of time and only then is the overvoltage signal transmitted to the control unit 10 , which triggers the pyro fuse 9 .

Claims (9)

Method for controlling a pyro fuse (9) provided in an electrical line (4) connecting the generator (6) and the starter (5) of a motor vehicle (1) to a battery (3) of the motor vehicle (1), which pyro fuse (9) is provided when a An accident signal indicating an accident in the motor vehicle (1) is actuated to disconnect the line (4) and is arranged in such a way that a part of an on-board network (2) of the motor vehicle (1) that is not connected to the battery (3) via the line (4) Triggering of the pyrofuse (9) can still be supplied from the battery (3), characterized in that the pyrofuse (9) for disconnecting the line (4) is also faulty when there is an overvoltage signal indicating an overvoltage at the generator (6) and a faulty one permanently closed switching device (14,15) for energizing the starter (5) indicating switch signal is controlled. procedure after claim 1 , characterized in that the battery (3) is a lithium battery. procedure after claim 1 or 2 , characterized in that to determine the overvoltage signal, a voltage measurement is carried out on the generator (6) and evaluated. procedure after claim 3 , characterized in that the overvoltage signal when a threshold value (24) for the voltage at the generator (6) is exceeded and/or when there is an overvoltage range defined in particular below the threshold value (24) but above a nominal voltage of the battery (3). (22) lying overvoltage at the generator (6) is given for a predetermined period of time. procedure after claim 4 , characterized in that a threshold value (24) is used, which corresponds to the maximum permissible charging voltage (23) of the battery (3) or exceeds it by a predetermined amount. procedure after claim 4 or 5 , characterized in that each overvoltage in the overvoltage range (22) is assigned a predetermined period of time using a characteristic curve (25) or a look-up table, in particular a predetermined period of time that decreases as the overvoltage increases. Method according to one of the preceding claims, characterized in that to determine the switch signal, a voltage measurement is carried out within the starter (5), in particular on a starter motor (18), and if an operating voltage is present without a desired operation of the starter (5) indicating start signal the switch signal is given. Method according to one of the preceding claims, characterized in that a control unit (10) assigned to the pyro-fuse (9) is used to actuate the pyro-fuse (9) and is supplied with the overvoltage signal and/or the switch signal from at least one diagnostic control unit (11). Motor vehicle (1) comprising an on-board network (2) with a battery (3), a starter (5), a generator (6) and a line connecting the starter (5) and the generator (6) to the battery (3). (4) which can be interrupted by a pyro fuse (9) after activation by at least one control device (10), which is arranged in such a way that a part of an on-board network (2) that is not connected to the battery (3) via the line (4) of the motor vehicle (1) can continue to be supplied from the battery (3) when the pyro fuse (9) is triggered, the control unit (10) being designed to carry out a method according to one of the preceding claims.

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