DE102010029806A1 - Electrical system for e.g. pure electric car, has power source that is selectively short-circuited by actuation of switch for terminating connection between power source and onboard network - Google Patents

Abstract

The system (10) has a control device (20) to activate a switch (18) to disrupt an electrical interconnection between an electrical power source (12) and an onboard network i.e. mains, based on a predetermined state detected by a sensor device (22). A short-circuit line (24) is provided with a defined discharging resistor (26) for controlled discharge of the power source. The short-circuit line is connected with the switch and the source such that the power source is selectively short-circuited by actuation of the switch for terminating the connection between the source and the network. The sensor device is a sensor for determining data of the driving conditions of a vehicle or an airbag sensor. The electrical power source is a lithium ion cell and comprises a thermal inactivatable separator.

Description

The invention relates to an electrical system for a vehicle.

State of the art

To reduce emissions from motor vehicles, hybrid concepts or pure electric drive concepts are currently being developed. The operation of electric machines in motor and generator operation requires an electrical power source or an electrical energy storage in the vehicle. On the one hand to ensure the necessary operational safety by maintaining the permissible voltage ranges of the cells and on the other hand to track the state of charge (SOC) of the batteries, so-called battery management systems (BMS) are used. Especially with electrically driven vehicles often voltages of several hundred volts are necessary, the corresponding battery provides power up to several hundred kilowatts. For safety reasons, an uncontrolled short circuit of individual cells or the entire battery is therefore essential to prevent. A fire or an explosion of the modules could otherwise be the result.

There are therefore safety devices for reducing the risk of persons in an accident with a vehicle comprising an electric motor are known, which are designed such that the connection of the main battery is interrupted to the corresponding electronic consumers in an accident.

That's how it is US 6,157,288 known to provide a fusible electrical connection, which melts in an accident by a heating Thermitkapsel and thus interrupts the flow of electrical current.

According to US 5,757,150 An electrical connection between the battery and consumers is interrupted by switches that are exploded by explosives in the event of an accident.

Out US 5,816,358 It is known to switch the electrical wiring system of the vehicle between the power source and the electric motors used for the driving operation after detecting an accident situation as early as possible by a contactor circuit by the switch contactor interrupts the electrical line connection.

In US 5,389,824 It is disclosed to separate the main battery by a circuit breaker with a switch from the mains.

In particular, in the event of an accident, further, it has not yet been sufficiently clarified what consequences a high mechanical load or a short circuit could have on a battery, such as a lithium-ion tent-pack. It is therefore desirable to prevent an abrupt release of the energy stored in the cells under all circumstances. Because it comes, for example, in a lithium-ion battery to a local short circuit of the internal electrodes, eg. B. because the separating separator is contaminated by an enclosed foreign particles, the short-circuit current can heat the surrounding area of the damaged area so far that the surrounding areas are also affected. This process expands and releases the stored energy in the accumulator abruptly. Such operations are referred to as thermal runaway and should be prevented for safety reasons.

The object of the invention is to provide an electrical system for a vehicle with which the dangers caused by an electric power source, such as after an accident, can be reduced or eliminated altogether.

Disclosure of the invention

The subject matter of the present invention is an electrical system for a vehicle, comprising an electric power source, in particular for driving an electric motor, and a switch, by means of which an electrical connection between the power source and vehicle electrical system of the vehicle can be selectively formed or interrupted, and a control device for this purpose is designed to operate in a detectable by a control device connected to the sensor device predetermined state, the switch to interrupt the electrical connection between the power source and the electrical system, characterized in that a short-circuit line is provided with a defined discharge resistor for controlled discharge of the power source , which is connected to the switch and the power source such that by operating the switch for disconnecting the connection of the power source and the onboard power supply, the power source is selectively short-circuited i st.

The electrical system according to the invention is particularly suitable for reducing, in a vehicle driven by an electric motor, the danger emanating from the power source at predetermined undesired or inadmissible states. Because especially when driven by an electric motor vehicles, it is necessary to adapt the performance as well as the range of conventionally powered vehicles. Such a high performance can be practically realized only with a high voltage and power supply. Vehicles that can be driven by an electric motor therefore often have power sources with voltages of several hundred volts, for example over 500 volts, providing powers of approximately 20 to 500 kW. Such voltage sources and electrical services naturally have great potential for danger, which endangers the occupants or other persons in the event of impermissible conditions.

The electrical system according to the invention can therefore safely reduce the danger emanating from the power source. Such a predetermined state may be, for example, a fault in the electrical system, such as impermissible voltages, currents, temperatures or the like. It is therefore advantageous if corresponding measuring devices or sensors are connected to the control device, which pass on voltage, current or temperature data to the control device. The control device then expediently has an evaluation unit or evaluation logic by means of which it can be recognized from the data whether the electrical system is in a normal state or in a faulty state.

If a faulty or impermissible state is detected by the sensor device, the switch is actuated by the control device, whereby the electrical connection between the power source and the vehicle electrical system is disconnected. As a result, the lines are de-energized within the vehicle, so that these cables of the electrical system do not form a hazard.

In addition, characterized in that the Leistungsqueue is short-circuited by the operation of the switch and in the short-circuit line a predefined discharge resistor, in particular a low-resistance load resistor is arranged, a short circuit closed with a defined resistance, whereby the power source discharges or controls the energy stored in the power source is reduced via the load resistor. The controlled degradation of at least a portion of the stored energy thereby reduces the potential hazard of the power source, such as spontaneous, uncontrolled energy degradation, such as a fire or explosion, after an accident or in case of failure. The power source thus loses its voltage, so that only a very small danger emanates from the power source itself.

In this case, the resistor preferably has a variable resistance value. Thereby, the degree of discharge as well as the heat generated by the short-circuit current can be adjusted or reduced.

In a preferred embodiment, the sensor device is designed as a sensor device for acquiring data of the driving situation of the vehicle. As a result, even a dangerous driving situation, in particular an accident of the vehicle, can be detected by the sensor (s) and passed on to the control device. The control device can then actuate the switch in such driving situations and thus disconnect the electrical power source from the electrical system. In this way, vehicle occupants as well as helping people after an accident can no longer be injured by electric shocks or the like. Therefore, according to the present invention, a predetermined state in which the switch is to be operated can also be an improper driving situation such as an accident.

It is particularly advantageous here if the sensor device is the sensor device of an airbag. As a result, the already existing in the vehicle peripherals or equipment can be used in a simple manner. In particular, an airbag sensor can deliver important and useful according to the invention, indicating an accident as a predetermined condition.

In the context of a further advantageous embodiment, the electrical power source comprises at least one lithium-ion cell. Due to their high energy density compared to other battery systems, lithium-ion cells are particularly advantageous for electrical systems according to the invention. In this case, the power source may in particular also comprise a plurality of lithium-ion cells, which are connected accordingly, in particular in series.

In the context of a further advantageous embodiment, the electrical power source has a thermally inactivatable separator. A separator is here an element that allows a circuit, but separates the different electrodes of the electric power source from each other and is thus elementary for the construction of the voltage. In this embodiment, it is exploited that a high heat energy is generated by the short-circuit current in the short-circuit line, in the discharge resistor but also in the electrical power source itself. The thermal energy generated by the short-circuit current thus deactivates the thermally inactivatable separator, with the result that the power source is irreversibly deactivated.

Inactivating the separator in the context of the invention means in particular that the separator becomes impermeable in such a way that the two Electrodes of the power source are completely separated, so the separator breaks the circuit. The inactivation therefore requires, according to the invention, an impermeability to ions. As a result, the power source is irreversibly deactivated and thus can no longer produce a terminal voltage at the battery poles. The power source then no longer has any risk potential.

For example, inactivation may be deforming, such as simple melting, in which the structure of the separator is changed to become impermeable to ions.

However, instead of melting it may also be advantageous that the thermal inactivation can be carried out by a chemical reaction. Inactivation may therefore also be a material change due to a chemical reaction that is activated by the heat generated by the short-circuit current. For example, a polymerization reaction is possible here.

To achieve a rapid and effective inactivation of the separator, it is therefore advantageous if the separator has an inactivation temperature or an inactivation point which is in the range from ≥ 60 ° C to ≦ 200 ° C, in particular in a range of ≥ 100 ° C. to ≤ 120 ° C, lies. It is fundamental that the inactivation point is above the operating temperature of the power source. The inactivation point is understood here to mean the temperature at which the separator is inactivated.

In particular, it is advantageous if the separator is made of plastic. The plastic can then have a low melting point, whereby a rapid deactivation of the separator and thus a rapid deactivation of the power source is possible.

In another embodiment, the discharge resistor and / or the short-circuit line and / or the power source is thermally connected to a cooling element. A cooling element may reduce or dissipate the heat generated by the short-circuit current from the short-circuit line and / or the discharge resistor and / or the power source and thus effectively prevent a thermal runaway when discharging the battery, for example. In particular, a cooling element protects adjacent vehicle parts and, for example, persons who are helping after an accident or are in the vehicle.

The subject matter of the present invention is furthermore a vehicle which has an electrical system according to the invention.

Further advantages and advantageous embodiments of the objects according to the invention are illustrated by the drawing and explained in the following description. It should be noted that the drawing has only descriptive character and is not intended to limit the invention in any way. It shows

1 a schematic representation of an electrical system according to the invention.

In 1 is an inventive electrical system 10 shown. The electrical system 10 is preferably part of a vehicle, which at least at times relates at least a portion of the drive torque via at least one electric motor. For example, this vehicle may be both a pure electric vehicle and a hybrid electric vehicle (HEV).

The electrical system 10 according to the invention comprises a power source 12 , The power source 12 can be any type of power source or voltage source that can be used for an electrically powered vehicle. Consequently, the power source is 12 a traction battery, which is designed in particular as an accumulator. Preferably, the power source 12 a lithium-ion cell or a plurality of lithium-ion cells or comparable cells or accumulators or primary batteries.

The power source 12 is via lines 14 . 16 connected to the vehicle electrical system. Under the electrical system of the vehicle is understood in particular the line network, which is connected to the one or more electric motors. In at least one of the lines, for example in the line 14 , is a switch 18 arranged. Through the switch 18 is the electrical connection between the power source 12 and the vehicle electrical system of the vehicle selectively formable or interruptible.

This is indicated by the switch 18 at least two switch positions, namely the position AB and the position AC. In the switch position AB is the electrical connection between the power source 12 and electrical system designed so that the power source 12 can supply the vehicle electrical system with energy. In this normal position of the switch 18 can be the power source 12 drive the electric motor (s). In contrast, in the switch position AC, the electrical connection between the power source 12 and the vehicle electrical system interrupted, the battery thus decoupled from the electrical system, so that a supply of the electrical system with energy is not possible. The switch position AC is the emergency position of the switch 18 ,

The electrical system according to the invention 10 further comprises a control device 20 that with the switch 18 connected is. The control device 20 is adapted to switch at a predetermined state 18 to press. This will make the switch 18 brought from its normal position AB in an emergency position AC.

A predetermined state is one in which an increased risk from the power source 12 can go out. In particular, these are conditions with unwanted or unacceptable voltage, current or temperature in the electrical system as well as damage to the vehicle, which damage the power source 12 can bring with it. A typical erfindungsgmäß predetermined state is here an accident of the vehicle.

To detect such a predetermined state, is a sensor device 22 intended. The sensor device 22 may include a single sensor, or preferably a plurality of sensors. Exemplary sensors are sensors for acquiring data of the driving situation of the vehicle, such as acceleration sensors that monitor the driving behavior of the vehicle. As a result, an accident of the vehicle can be detected. Suitable sensors for detecting an accident situation are, in particular, those sensors which determine a longitudinal or lateral acceleration of the vehicle. Separate sensors can be used. Advantageously, however, it is possible to resort to sensors already in the vehicle, such as those of an airbag system. In this case, it is also advantageous if the control unit 20 the control unit with evaluation logic of the airbag system is. Then in an accident, the decoupling of the power source 12 be coupled by the electrical system to the deployment of the airbag.

In addition, the sensor device 22 include other sensors such as current, voltage or temperature sensors to detect a faulty operating state of the electrical system.

Will now be such a predetermined state of the sensor device 22 detected or detected and by the control device 20 evaluated, causes the controller 20 a switchover of the switch 18 from its normal position AB to the emergency position AC. In this way, the electrical connection of the power source 12 and the electrical system interrupted and so the power source 12 disconnected from the electrical system. The electrical system is therefore no longer with the electrical power source 12 and thus connected to the high voltage, so that an increased risk from the electrical system no longer runs out. The switching time from the normal position AB of the switch 18 in the emergency position AC should be in a range ≤ 50 ms, more preferably ≤ 35 ms.

In addition to the electrical disconnection of the power source 12 of the electrical system is inventively provided that the power source 12 is at least partially unloaded. This is a short circuit line 24 provided with the switch 18 as well as with the power source 12 connected is. Here is the short circuit line 24 arranged such that upon actuation of the switch 18 in its emergency position AC the power source 12 shorted. In the short circuit line 24 is a resistance element as a discharge resistor 26 arranged by the occurrence of a discharge current, the power source 12 at least partially, preferably completely discharged.

In an at least partially discharged state is also from the power source 12 even a much lower risk.

Especially if the power cell 12 a lithium-ion cell or a lithium-ion battery, a separator is arranged in this, which separates the two electrodes spatially and electrically from each other. Particularly suitable materials for the formation of the separator are in particular plastics, such as microporous plastics, and glass fiber nonwovens or polyethylene used. In order to reduce the risk even further, it is provided in a development of the invention that this separator is thermally inactivated. As a result, the separator, due to the heat generated by the short-circuit current in the short-circuit line 24 as well as in the discharge resistor 26 and in particular in the power source 12 is generated, inactivated or becomes impermeable, whereby the ion flow is impossible. The power source 12 is then irreversibly disabled, creating a threat from the power source 12 is essentially completely excluded.

The discharge resistance 26 should be selected so that the short-circuit current deactivates the separator but does not cause any uncontrolled reactions, such as a thermal runaway. This can be achieved, for example, by the discharge resistor 26 has a variable resistance. Because by the setting of the resistance, the discharge of the power source 12 as well as the heat generated by the short-circuit current are regulated and adjusted.

The resistance of the discharge resistor 26 should be adjustable so that he reaches a minimum value, whereby a maximum short-circuit current flows. The value of the short-circuit current determines the discharge speed. The cheapest resistance value is system-dependent. The minimum resistance R _min results from the quotient of the minimum voltage of the electrical power source U _Leist and the current I _inact which can inactivate the separator by the generated heat. Therefore, the minimum resistance value is calculated according to R = U _{min Leist} / I _inact. Due to the high heat generated, it is also advantageous if in particular the discharge resistor 26 is arranged in a well-ventilated and safe to touch location in the vehicle so as to prevent unwanted hazards. For example, the resistance at the underbody of the vehicle may be similar to the hot exhaust train in conventionally powered vehicles.

In addition, it is possible to provide cooling elements through which the short-circuit line 24 as well as the discharge resistance 26 or the power source 12 is cooled. As a result, on the one hand an unwanted uncontrolled reaction, such as a thermal runaway can be prevented. In addition, it is possible, although the power source 12 over the short circuit line 24 but disabling the separator and thus deactivating the power source 12 to selectively prevent.

As a result, depending on what kind of predetermined state of the sensor 22 is detected, various approaches in particular by the controller 20 to be triggered. For example, if there is a fault in the electrical system, a so-called mild discharge may take place. In this case, the resistance value of the discharge resistor 26 be set comparatively high. In this case, although the power source 12 discharged, but inactivation of the separator does not take place due to the low heat. The power source 12 can be recharged and used afterwards.

For this it is advantageous if the control device 20 in the case of a mild discharge, the switch 18 pressed again to bring it back to its normal position AB. It can thus be provided that the control device 20 the switch 18 depending on the state of the vehicle, not only returns from its normal position AB to its emergency position AC, but also from its emergency position AC back to its normal position AB. This can be done both automatically, as described above, as well as manually, by an input of the driver, for example by pressing an input unit on the dashboard of the vehicle.

Accordingly, in an accident can be set very low as a predetermined state, the resistance value, in particular more than or exactly according to the above formula R = U _{min Leist} / I _inact to a rapid discharge of the power source 12 and at the same time generate a great deal of heat so that the separator inactivates.

It is advantageous if the cooling elements and / or the discharge resistor 26 with the control device 20 are connected so that it performs a cooling and an adjustment of the resistance value depending on the occurred state. As a result, the electrical system can react selectively to the situation that has occurred, for example faulty system or accident.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 6157288 [0004]
• US 5757150 [0005]
• US 5816358 [0006]
• US 5389824 [0007]

Claims (10)

Electrical system for a vehicle, comprising an electric power source ( 12 ), in particular for driving an electric motor, and a switch ( 18 ), through which an electrical connection between power source ( 12 ) and vehicle electrical system of the vehicle is selectively formable or interruptible, and a control device ( 20 ), which is adapted, at one of a with the control device ( 20 ) connected sensor device ( 22 ) detectable predetermined state the switch ( 18 ) to control the electrical connection between the power source ( 12 ) and electrical system, characterized in that a short-circuit line ( 24 ) having a defined discharge resistance ( 26 ) for controlled discharging of the power source ( 12 ) provided with the switch ( 18 ) and the power source ( 12 ) is connected in such a way that by actuating the switch ( 18 ) to disconnect the service queue ( 12 ) and electrical system the power source ( 12 ) is selectively short-circuitable. Electrical system according to claim 1, characterized in that the discharge resistor ( 26 ) has a variable resistance value. Electrical system according to one of claims 1 or 2, characterized in that the sensor device ( 22 ) is formed as a sensor for acquiring data of the driving situation of the vehicle. Electrical system according to claim 3, characterized in that the sensor device ( 22 ) is the sensor device of an airbag. Electrical system according to one of claims 1 to 4, characterized in that the electrical power source ( 12 ) comprises at least one lithium-ion cell. Electrical system according to one of claims 1 to 5, characterized in that the electrical power source ( 12 ) has a thermally inactivatable separator. Electrical system according to claim 6, characterized in that the separator has an inactivation temperature which is in the range of ≥ 60 ° C to ≤ 200 ° C, in particular in a range of ≥ 100 ° C to ≤ 120 ° C. Electrical system according to one of claims 6 or 7, characterized in that the thermal inactivation by a melting and / or a chemical reaction is executable. Electrical system according to one of claims 1 to 8, characterized in that the discharge resistor ( 26 ) and / or the short-circuit line ( 24 ) and / or the power source ( 12 ) is thermally connected to a cooling element. Vehicle, characterized in that the vehicle is an electrical system ( 10 ) according to one of claims 1 to 9.

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