DE102016008057A1 - Electric energy storage with discharge circuit - Google Patents

Abstract

The invention relates to an electrical energy store (10) for an electrical system (12) of an electrically driven motor vehicle, comprising at least two energy storage connections (14, 16), at least one galvanic cell (18), a contactor (20), which is for each of the energy storage connections (14, 16) a switching element (22, 24) for the controlled electrical connection of the at least one galvanic cell (18) with the energy storage terminals (14, 16), and a control unit (26) for controlling the contactor (20), wherein the electrical energy store (10) has a to the energy storage terminals (14, 16) connected and controllable by means of the control unit (26) discharge circuit (28) for consuming electrical energy.

Description

The invention relates to an electrical energy store for an electrical system of an electrically driven motor vehicle, with at least two energy storage terminals, at least one galvanic cell, a contactor, which has a switching element for controlled electrical connection of the at least one galvanic cell with the energy storage terminals for each of the energy storage terminals, as well a control unit for controlling the contactor.

Electrical energy storage, electrical systems with such electrical energy storage, as well as motor vehicles of the generic type are known in the art, so that in this respect the reason of a separate documentary proof is not required. The electrical system of the motor vehicle serves to distribute electrical energy between electrical units of the motor vehicle comprised by the electrical system. In addition to an electrical energy store, electrical consumers and / or the like, such units may also be an electrical energy source such as a generator, a fuel cell or the like, and in particular in the case of electrically driven vehicles also an electric drive device which serves to drive the electrically driven motor vehicle. In addition, a number of other electrical units, for example a lighting unit, headlights of the motor vehicle, interior lighting of the motor vehicle and / or the like, but also further functional units such as a car radio, a navigation device, an electrically driven air conditioning compressor and / or the like may be included.

An electrically driven motor vehicle is, for example, an electric vehicle, a hybrid vehicle and / or the like. The motor vehicle is preferably a motor vehicle, in particular a passenger car.

Not only but especially in electrically driven motor vehicles, especially in electric vehicles, the electrical system with a high electrical voltage, in particular a DC voltage, for example, of about 400 V or more, is applied. The size of this electrical voltage is above all a challenge for safety reasons, which is why, for example, special safety requirements must be observed here, which are specified in particular by standardization. For example, by the Standard ECE R100 specified that at an electrical DC voltage greater than 60 V special measures to protect people from electric shock are provided. For this reason, for example, in an electrical energy storage, which may be formed as an accumulator, which is used for example as a traction battery, provided in such an electrical system that the electrical energy storage, also called high-voltage battery, is equipped with an integrated contactor, which due to corresponding control electrical energy storage terminals of the electrical energy storage device, which are electrically connected to corresponding lines of the electrical system, can be electrically separated from the galvanic cells of the electrical energy storage device, which provide its voltage. This device has basically been granted, but there are disadvantages.

In particular, after an accident but also during maintenance of the electrical system or the motor vehicle, it would be advantageous if it could be ensured that an electrical potential of dangerous size could not be touched on the motor vehicle at an undesired location, for example because it is exposed, so that at Touch could endanger people. This case can occur, for example, if the motor vehicle was used shortly before the start of activities on the electrical system or the like during normal operation. In this case, a so-called DC voltage intermediate circuit of the electrical system is still energized, even if the electrical energy storage is already deactivated by means of the contactor provided in it. This results from the basic design of the electrical system, which provides its own energy storage capacity due to capacitive elements, for example by an intermediate circuit capacitor, which is provided by an inverter of the drive device for the motor vehicle and / or the like. Although the DC intermediate circuit is usually discharged over time, for example by the connected electrical units having a certain own power consumption, but usually very large time constants are present, so that when working on the electrical system dangerous electrical potentials may be present.

A similar problem can also occur in an accident in which the motor vehicle is damaged and any security measures, for example, to secure people or the like, must be made. In the event of unfavorable damage to the motor vehicle due to the accident, it may happen that lines exposed to electrical potential can be touched by the electrical system or the DC intermediate circuit or when parts arranged in an isolated condition can be contacted and disposed in an undamaged state thereby making dangerous electrical potentials accessible. This problem can not only arise if the electrical energy storage is not switched off due to a defective contactor, but also due to an intrinsic capacity of the electrical system.

To bring about an improvement here it is for example from the DE 10 2008 061 585 A1 known to connect to a DC voltage intermediate circuit, a discharge circuit, by means of which the intermediate circuit can be discharged when the electrical energy storage is deactivated by means of the contactor. For this purpose, an operating state signal is detected, so that the discharge circuit is activated when the motor vehicle is outside a normal driving operation. Although this doctrine causes an improvement, there are still disadvantages. For example, it proves to be disadvantageous that the discharge circuit is to be arranged as a separate assembly in the electrical system. As a result, faults can occur, in particular if contact problems occur in the field of connection technology with increasing aging, the discharge circuit is damaged in the event of an accident, or the like. The function of the discharge circuit is also not checked.

The invention is therefore based on the object to improve the electrical safety of an electrically driven motor vehicle.

As a solution, an electrical energy storage device according to claim 1 is proposed with the invention.

Further advantageous embodiments result from features of the dependent claims.

With regard to the electrical energy storage device, it is proposed, in particular, that it has a discharge circuit connected to the energy storage connections and controllable by the control unit for consuming electrical energy.

The invention makes use of the knowledge that a safety device, which is in any case required for the operation of the electrical energy store, is already present in the electrical energy store with a corresponding control unit. It proves to be particularly advantageous if the discharge circuit is also included in the electrical energy storage and preferably can also be controlled by this control unit. This can also be avoided, inter alia, that in a defective contactor, the discharge circuit is activated, although the electrical energy storage or the galvanic cells are not yet separated from the electrical system by means of the contactor. If, in fact, the discharge circuit is not designed to discharge the electrical energy store or its galvanic cells, this can result in destruction of the discharge circuit. With the invention can thus be ensured that the safety can be further improved by monitoring the switching elements of the contactor, in particular their functions.

In this context, it proves to be advantageous, of course, if the discharge circuit is designed to be able to simultaneously enable a discharge of the galvanic cells of the electrical energy storage. As a result, it can be ensured, in particular in the event of an accident, that the electrical energy stored in the electrical energy store can not cause dangerous states. This can occur, for example, if the electrical energy store itself is damaged or due to damage to the electrical energy store the contactor is unable to properly separate the galvanic cells from the electrical system.

But regardless of this can be achieved with proper deactivation of the galvanic cells, a fast and reliable discharge of the DC voltage intermediate circuit or the electrical system, even if due to damage to the electrical system is no longer fully functional. A reliable discharge can therefore be ensured even if at the DE 10 2008 061 585 A1 the discharge circuit itself would be damaged or a power supply for their intended operation would no longer be available. Namely, in the present invention, the discharging circuit can directly draw electric power required for its intended operation from the galvanic cells. In this respect, increased reliability can be achieved.

It proves to be particularly advantageous if the discharge circuit for detecting an accident signal is electrically coupled to an accident detection device of the motor vehicle, wherein the discharge circuit is designed to be automatically activated upon detection of the accident signal of the accident detection device. The activation can be carried out at the same time with a corresponding actuation of the contactor, by means of which the galvanic cells are separated from the electrical system. For this purpose, the evaluation of a signal at a terminal 30c of the electrical system of the motor vehicle can be used. A signal at this terminal is also often used to trigger, for example, an airbag of the motor vehicle.

The switching elements of the contactor can be designed as electromechanical switching elements and / or as electronic switching elements. If they are designed as electronic switching elements, they can be formed, for example, by a semiconductor switch, for example a bipolar transistor operated in switching mode, a field-effect transistor operated in switching operation, combinations thereof and / or the like.

The discharge circuit preferably has at least one electrically controllable element for consuming the electrical energy. The controllable element can be formed for example by a transistor, a bipolar transistor, a field effect transistor, combinations thereof and / or the like. So that a corresponding energy consumption can be achieved in a predeterminable manner, the electrically controllable element is preferably operated in a linear mode, so that a control can be achieved depending on the energy to be converted and the discharge speed. For this purpose, the electrically controllable element can be connected, for example, to a heat sink, for example a heat sink and / or the like.

In addition, it can of course be provided that the discharge circuit comprises a series connection of an electrically controllable element and an electrical resistance for consuming the electrical energy. In this way, the loss of the electrically controllable element can be reduced.

It proves to be particularly advantageous if the electrically controllable element is formed by an electrically controllable switching element, which may be formed, for example, as an electromechanical switching element or as an electronic switching element. An electronic switching element may be, for example, a transistor which is operated in the switching mode. Again, the transistor may again be a bipolar transistor, a field effect transistor and / or the like. In this embodiment, the predominant part of the electrical energy to be consumed is preferably converted into heat by the electrical resistance connected in series therewith. In this respect, the electrically controllable element essentially only has to be configured electrically for the requirements of the discharge circuit. Furthermore, the energy to be consumed can thereby be consumed in a simple manner at a point at which it can be discharged as well as possible or influences the environment as little as possible.

Preferably, therefore, the discharge circuit or the electrically controllable element and / or the electrical resistance is connected to a cooling unit as a heat sink. The cooling unit may be formed by a heat sink, which is cooled, for example by means of air or by means of a coolant. For this purpose, the discharge circuit may also include a corresponding cooling device, which allows to dissipate the energy consumed, which is preferably obtained in the form of heat. It can thereby be achieved that the discharge circuit can also convert large amounts of energy in a short time. This embodiment is particularly advantageous if the discharge circuit is at the same time also intended to be able to discharge the galvanic cells of the electrical energy store. As a rule, the galvanic cells are designed to be able to store a large amount of electrical energy. If the galvanic cells are maximally charged, a correspondingly large amount of energy is available which, for example in the event of an accident, can be implemented by means of the discharge circuit. This can be enabled by a suitable cooling device.

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the figure description and / or alone in the single figure can be used not only in the respectively indicated combination but also in other combinations or alone, without the frame to leave the invention.

Showing:

1 A schematic block diagram of a high-voltage battery, which is connected to an electrical system with a discharge circuit according to the invention.

It shows the only one 1 in a schematic block diagram view, an electrical energy storage, in the present case as a high-voltage battery 10 is designed for an electrical system 12 a not shown electrically driven motor vehicle. The electrical system 12 is shown here only as a block and includes not only an electrical drive device for the motor vehicle further electrical units such as an air compressor, an electric roll stabilization, electrical lighting devices and the like. The electrical system 12 further comprises a DC intermediate circuit 38 which in turn has electrical wiring 40 . 42 includes.

To the electrical wires 40 . 42 are battery connections 14 . 16 as energy storage connections of the high-voltage battery 10 connected by means of which the high-voltage battery 10 to the electrical system 12 connected. In the present case is the battery connection 14 to the electrical line 40 connected, which is acted upon by a HV + potential. The battery connection is the same 16 to the electrical line 42 connected, which is acted upon by a HV - potential.

The high-voltage battery 10 further comprises an unspecified number of galvanic cells connected in series 18 , which are formed here as lithium-ion cells. By means of the galvanic cells 18 is provided by the series connection, a DC electrical voltage, which in the present case is about 400 V.

The galvanic cells 18 are present over a contactor 20 to the battery connections 14 . 16 connected. The contactor 20 has two switching elements 22 . 24 on, which are presently designed as electronic switching elements. The switching elements 22 . 24 are formed by MOSFETs (metal oxide semiconductor field effect transistor) connected to a control unit 26 connected in the high-voltage battery 10 is arranged integrated. By means of the control unit 26 can the switching elements 22 . 24 be controlled in a predeterminable manner, so that the galvanic cells 18 for the intended operation of the motor vehicle over the contactor 20 with the battery connections 14 . 16 are electrically coupled, so that between the electrical wires 40 . 42 through the galvanic cells 18 provided electrical DC voltage is applied.

The control unit 26 is further to an accident detection device 34 of the motor vehicle electrically connected. The electrical connection is in the present case made via a not further shown BUS system of the motor vehicle. In the present case, the BUS system is designed as a CAN-BUS. The accident detection device 34 is formed when detecting an accident of the motor vehicle, an accident signal 36 leave. This signal is from the control unit 26 then detects the switching contacts 22 . 24 of the contactor 20 opens. As a result, then the galvanic cells 18 from the DC intermediate circuit 38 separated.

The high-voltage battery 10 further includes a discharge circuit 28 , Which in the present case consists of a series connection of an electrically controllable element, which in the present case is a semiconductor switch 30 is, with an electrical resistance 32 is formed. The discharge circuit 28 is to the battery connections 14 . 16 connected. This is what it is with the battery connections 14 . 16 directly connected. The electrically controllable element 30 is in turn also to the control unit 26 connected. This allows the discharge circuit 28 - unlike the galvanic cells 18 - through the contactor 20 not from the electrical system 10 be separated.

In the present case, it is provided that the control unit 26 the switch contacts 22 . 24 of the contactor 20 complementary to the electrically controllable element 30 controls, so that when the switch contacts 22 . 24 are closed and the galvanic cells 18 as a result with the battery connections 14 . 16 are electrically coupled, the electrically controllable element 30 in the open state, so that the discharge circuit 28 is disabled. Are however the switching contacts 22 . 24 in the open state to the galvanic cells 18 from the battery connections 14 . 16 to separate, however, is the electrically controllable element 30 in the closed state, leaving the discharge circuit 28 is activated. In this operating state discharges the discharge circuit 28 the DC intermediate circuit 38 the electrical system 12 ,

In the present case, it is provided that a time constant for the discharge by means of the discharge circuit is chosen such that a discharge to a low voltage, that is, a DC electrical voltage of less than 60 V, takes place within one second. Preferably, a shorter time may be provided, for example, half a second, 50 milliseconds or less.

Furthermore, it is provided in the present case that the electrically controllable element 30 while in the closed state remains until the control unit 26 the switching elements 22 . 24 should proceed again in the closed state. If this condition should be taken, before the electrically controllable element 30 opened and thus the discharge circuit 28 disabled. This can be achieved that the discharge circuit 28 not with electrical energy from the galvanic cells 18 is charged. The discharge circuit 28 therefore only needs for the discharge of the DC voltage intermediate circuit 38 the electrical system 12 to be designed.

But it can also be provided that a voltage state of the DC voltage intermediate circuit 38 is detected and falls below a predetermined reference voltage, the switching element 30 from the control unit 26 is opened again. This will cause the DC link 38 the electrical system 12 only so far discharged that no unacceptably high electrical voltage in relation to the electrical safety in the electrical system 12 more is available.

In the present case it is further provided that the control unit, the discharge circuit 28 always then activated when the motor vehicle has finished its intended driving operation.

In an alternative embodiment, moreover, it can be provided that the control unit 26 an accident signal 36 evaluates and the switching elements 22 . 24 opens and at the same time the switching element 30 closes, so that the DC link 38 unloaded. The control unit 26 may also be configured to detect whether the high-voltage battery 10 has been damaged. If such damage can be detected, the control unit can 26 further be adapted to the switching elements 22 . 24 upon detection of the accident signal 36 continue to be closed and at the same time the electrically controllable element 30 the discharge circuit 28 to close, in addition to a discharge of the DC intermediate circuit 38 also a discharge of the galvanic cells 18 to enable. For this operating state is the discharge circuit 28 interpreted accordingly, since usually the galvanic cells 18 provide a much larger amount of electrical energy than the capacity of the DC link 38 ,

Preferably, the discharge circuit 28 connected in a manner not shown to a corresponding cooling device, which allows to dissipate the preferably converted into heat electrical energy or supply a heat sink.

The embodiment is merely illustrative of the invention and is not limitative of it. Furthermore, it should be noted that the advantages and features and embodiments given for the energy store according to the invention apply equally to the electrical system and to the corresponding electrically drivable motor vehicle or a corresponding method and vice versa. In particular, device features can therefore also be provided according to process features.

LIST OF REFERENCE NUMBERS

10

High-voltage battery

12

Electrical system

14

Batterieanschuss

16

battery terminal

18

galvanic cells

20

contactor

22

switching element

24

switching element

26

control unit

28

discharge

30

Semiconductor switches

32

resistance

34

Crash detector

36

accident signal

38

Dc link

40

electrical line

42

electrical line

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

• DE 102008061585 A1 [0007, 0014]

Cited non-patent literature

• Standard ECE R100 [0004]

Claims (7)

Electric energy storage ( 10 ) for an electrical system ( 12 ) of an electrically driven motor vehicle, with at least two energy storage connections ( 14 . 16 ), at least one galvanic cell ( 18 ), a contactor ( 20 ), which for each of the energy storage connections ( 14 . 16 ) a switching element ( 22 . 24 ) for the controlled electrical connection of the at least one galvanic cell ( 18 ) with the energy storage connections ( 14 . 16 ), and a control unit ( 26 ) for controlling the contactor ( 20 ), characterized by a to the energy storage terminals ( 14 . 16 ) and connected by means of the control unit ( 26 ) controllable discharge circuit ( 28 ) for consuming electrical energy. Electrical energy store according to claim 1, characterized in that the discharge circuit ( 28 ) an electrically controllable element ( 30 ) for consuming the electrical energy. Electrical energy store according to claim 1 or 2, characterized in that the discharge circuit ( 28 ) a series connection of the electrically controllable element ( 30 ) and an electrical resistance ( 32 ) for consuming the electrical energy. Electrical energy store according to claim 3, characterized in that the electrically controllable element ( 30 ) is formed by an electrically controllable switching element. Electrical energy store according to one of claims 1 to 4, characterized in that the discharge circuit ( 28 ) is connected to a cooling unit. Electrical energy store according to one of claims 1 to 5, characterized in that the discharge circuit ( 28 ) for detecting an accident signal ( 36 ) with an accident detection device ( 34 ) of the motor vehicle is electrically coupled, wherein the discharge circuit ( 28 ) is formed upon detection of the accident signal ( 36 ) of the accident detection device ( 34 ) to be activated automatically. Electrical energy store according to one of claims 1 to 6, characterized in that the discharge circuit ( 28 ) is formed at least in relation to a power in the galvanic cell ( 18 ) consume stored electrical energy.

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