Abstract:
In a vehicle electrical system, a method supplies a number of consumers of the system, which consumers are classified with different safety classifications, the differently classified consumers being supplied power from either one or more of a plurality of electrical subsystems according to their classifications or lack of classification.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is the national stage of International Pat. App. No. PCT/EP2015/067614 filed Jul. 31, 2015, and claims priority under 35 U.S.C. §119 to DE 10 2014 219 133.5, filed in the Federal Republic of Germany on Sep. 23, 2014. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a vehicle electrical system, in particular to a vehicle electrical system for a motor vehicle having a plurality of consumers, and to a method for supplying consumers in a vehicle electrical system of a motor vehicle. 
       BACKGROUND 
       [0003]    Vehicle electrical systems in motor vehicles have a multitude of electrical consumers that are supplied with electrical energy from an energy supply, e.g., as a battery or a generator. In addition, vehicle electrical systems also have electromechanical or electronic components such as switches and voltage converters. 
         [0004]    The electrical energy in the motor vehicle should be available such that the motor vehicle is able to be started at any time and a sufficient current supply is ensured during the operation so that, as a minimum, safety-related devices such as the brakes, the steering system and also the lights are supplied in a reliable and uninterrupted manner. In the off state, electrical consumers should still be operable for an adequate period of time without making a subsequent start impossible. It should be noted that an interruption in the supply of the consumers may occur in case of a malfunction in the voltage supply or a short-circuit in the vehicle electrical system, which in turn results in a failure of functionalities of the motor vehicle. 
         [0005]    The introduction of novel electronic and mechatronic systems in the motor vehicle, such as electrical steering systems or novel assistance systems, e.g., the brake assistant or an adaptive cruise control, which lower the energy consumption of the vehicle and markedly enhance the safety and comfort for the driver, is currently on the rise. In the future, further systems that allow for autonomous or partially autonomous driving are in the planning stage or are currently being developed. If such systems are installed in a vehicle, they, too, must operate reliably and meet the demands of functional safety. Specifically to be avoided in this context are what are termed common cause errors or single errors, which then lead to an abrupt malfunction of the entire system or subsystem. 
         [0006]    Thus, the use of such new systems also places higher demands on the safety and availability of the vehicle electrical system inasmuch as these systems are, for the most part, supplied from the standard 12V vehicle electrical system of the vehicle. Vehicle electrical systems with a higher voltage are also used, especially for commercial vehicles. Under no circumstances should a failure of the vehicle electrical system on the basis of a single error lead to a failure of a safety-related system that is indispensable for the safe functioning of the vehicle and which draws its energy from the 12V vehicle electrical system. 
         [0007]    A single fault, such as a short circuit in the vehicle electrical system or the failure of a battery or the generator, should not lead to the loss of the steering or braking ability of the vehicle. A defect of this type may also not lead to the abrupt failure of a system for the autonomous or partially autonomous control of the vehicle, for example. A driver of an automobile who relies on the system and possibly just happens to be inattentive might then perhaps react too late or incorrectly in the event of a sudden failure, which could lead to a dangerous situation. 
         [0008]    The currently most frequently installed vehicle electrical system with a generator and a 12V battery is largely sufficient for the presently installed electrical systems. Novel safety-related systems, whose function is indispensable for the safe operation of the vehicle, require novel vehicle-electrical system topologies, which ensure the energy supply for these safety-related consumers in a reliable manner. 
         [0009]    As already mentioned, safety-relevant consumers that carry out important functions in the motor vehicle and must not fail under any circumstances are provided in modern vehicle electrical systems to an increasing extent. In order to ensure this, it is known to connect safety-related consumers to one or multiple vehicle electrical subsystems, each vehicle electrical subsystem having its own energy supply that may include a battery and/or a generator, for instance. In the event of a failure of the energy supply of a vehicle electrical subsystem, safety-related consumers are able to be supplied from other vehicle electrical subsystems and can thereby maintain their operation. 
         [0010]    The printed publication DE 10 2005 004 330 A1 describes a vehicle electrical system for safety-related consumers, which includes at least two vehicle electrical subsystems, in which a safety-related consumer is to be supplied with a supply voltage via two different supply paths, the supply paths being able to be decoupled from each other with the aid of decoupling means. In addition, the safety-related consumer is able to be connected to at least two energy accumulators by way of at least four supply paths. 
         [0011]    Known from the printed publication DE 102 51 589 A1 is a vehicle electrical system having at least two vehicle electrical subsystems in which a respective supply voltage is available. Provided in the vehicle electrical system is a safety-related consumer, which is connected to one of the vehicle electrical subsystems. A supply voltage is able to be applied to this consumer via two different supply paths, and the supply paths are able to be decoupled from each other with the aid of decoupling means, such a switches. 
       SUMMARY 
       [0012]    Against this background, example embodiments of the present invention provide a vehicle electrical system and a method. 
         [0013]    According to an example embodiment of the present invention, the vehicle electrical system is designed to supply electrical energy from one of at least two electrical subsystems to consumers having what is termed an average safety relevance. For this purpose, the consumer is connected to the vehicle electrical subsystems by way of switches, for instance, and can be connected between the two vehicle electrical subsystems in a symmetrical manner. In addition, consumers without safety relevance are provided, which are likewise supplied with energy. It is of course possible to provide further consumers with a high safety relevance. 
         [0014]    Thus, topologies of vehicle electrical systems are introduced that ensure a reliable supply of safety-related consumers and supply the “usual” consumers in an efficient manner. This is achieved with little effort. The main focus is on topologies that supply consumers of average safety relevance and no safety relevance. 
         [0015]    A vehicle electrical subsystem is characterized by its own energy supply, which is typically independent of the other vehicle electrical subsystems. For example, a battery and/or a generator can serve as energy supply. In addition, a vehicle electrical subsystem can be equipped with an energy accumulator. 
         [0016]    Consumers in the vehicle electrical system are allocated to devices or components of the vehicle such as electronic brake systems, light systems and electronic steering systems. Depending on the assigned component, the respective consumer is assigned a safety classification. 
         [0017]    For example, each vehicle electrical subsystem is supplied with energy via a base vehicle electrical system from a generator situated therein; the vehicle electrical subsystem is separated from the base vehicle electrical system by a voltage converter or a switch and can have a separate energy accumulator so that consumers in this vehicle electrical subsystem are able to be supplied at a high voltage quality and with great reliability. In addition to the consumers, it is also possible to provide monitoring devices in the vehicle electrical subsystems. 
         [0018]    Additional advantages and further developments of the present invention result from the description and the attached drawings. 
         [0019]    It is understood that the aforementioned features and the features still to be discussed in the following text can be used not only in the respective combination indicated, but also in other combinations or can be used on their own without departing from the scope of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a diagram of a circuit system according to an example embodiment of the present invention. 
           [0021]      FIG. 2  is a diagram of a circuit system according to another example embodiment of the present invention. 
           [0022]      FIG. 3  is a diagram of a circuit system according to another example embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Example embodiments of the present invention are schematically shown in the figures and are described in detail in the following text with reference to those figures. 
         [0024]    Consumers are basically able to be subdivided into multiple categories in accordance with their safety relevance. The topologies introduced in the following text are based on consumers of the following three categories.
       Consumer R 1 : high safety relevance and redundant supply, where the consumer is assigned a high safety classification;   Consumer R 2 : average safety relevance, where the consumer is assigned an average safety classification; and   Consumer R 3 : no safety relevance, where the consumer is assigned no safety classification.       
 
         [0028]      FIG. 1  shows a vehicle electrical system  10  according to an example embodiment, in which a consumer having an average safety relevance is supplied from two vehicle electrical subsystems. The illustration shows a first vehicle electrical subsystem  12  and a second vehicle electrical subsystem  14 . A first generator  16  and a first battery  18  are allocated to first vehicle electrical subsystem  12 . A second generator  20  and a second battery  22  are allocated to second vehicle electrical subsystem  14 . In addition, the illustration shows a consumer R 3   a    24 , a consumer R 2   26 , and a consumer R 3   b    28 . Moreover, a first switch unit  30  having a first switch  32  and a first diode  34  as well as a second switch unit  40  having a second switch  42  and a second diode  44  are depicted. 
         [0029]    Hereinafter, consumers R 3   a    24  and R 3   b    28  are independent consumers of safety category  3 , or in other words, they are consumers without safety relevance. This means that no redundant supply of a consumer is involved as would be the case with consumers of category  1 , i.e., consumers of high safety relevance. Consumer R 2   26  is a consumer of safety category  2  and thus a consumer of average safety relevance. It is disposed symmetrically with respect to the two vehicle electrical subsystems  12 ,  14 . 
         [0030]    The consumers are integrated into vehicle electrical system  10  in accordance with this classification. As described at the outset, in the vehicle electrical system topologies introduced herein, consumers having at most an average safety relevance are supplied predominantly or even exclusively. Vehicle electrical system  10  of  FIG. 1  is basically made up of the two vehicle electrical subsystems  12 ,  14  to the left and right; each has a generator  16  or  20  and battery  18  or  22 , which supply a consumer of average safety relevance, i.e., consumer R 2   26 , by way of intelligent switch units  30 ,  40 . Intelligent switch units  30 ,  40  have a diode function, which means that they permit a current flow only from one of the vehicle electrical subsystems  12  or  14  to consumer R 2   26 . In the event that a source, e.g., a generator  16  or  20 , of a vehicle electrical subsystem  12  or  14  causes an overvoltage, respective intelligent switch unit  20  or  40  carries out a separation as well. Generators  16 ,  20  may exist as two separate generators  16 ,  20  or as two generators  16 ,  20  on a shaft and possibly inside a housing. 
         [0031]    The advantage of the topology in  FIG. 1  is that if either the right or the left vehicle electrical subsystem  12  or  14  fails completely, e.g., also with a short circuit, the supply of consumer R 2   26  is still ensured on a permanent basis. In theory it is also possible to supply a plurality of consumers of category  2  in parallel. However, it must then be ensured that no such consumer causes a short circuit or an overvoltage that leads to the failure of the other consumers. 
         [0032]    If no permanent supply independent of a random single fault is required, then an example topology according to  FIG. 2  can be selected, including a vehicle electrical system having two vehicle electrical subsystems, including a battery in each case, which are supplied from a generator.  FIG. 2  shows a vehicle electrical system, which is denoted by reference numeral  100  as a whole. It includes a first vehicle electrical subsystem  102  and a second vehicle electrical subsystem  104 . Both vehicle electrical subsystems  102 ,  104  are allocated a generator  106 . It supplies a first battery  108  in first vehicle electrical subsystem  102  and a second battery  110  in second vehicle electrical subsystem  104 . 
         [0033]    The illustration furthermore shows a first switch unit S 1   a    120  having a first switch  122  and a first diode  124 , a second switch unit S 1   b    130  having a second switch  132  and a second diode  134 , a third diode D 2   a    140 , a fourth diode  142 , a consumer R 3   a    150 , a consumer R 2   152 , as well as a consumer R 3   b    154 . 
         [0034]    In this specific example embodiment, a generator is dispensed with and the two vehicle electrical subsystems  102 ,  104 , each having a respective battery  108  and  110 , are supplied via a single generator, i.e., generator  106 , and if necessary, are decoupled from it via intelligent switch units S 1   a    120 , S 1   b    130 . If generator  106  causes a short circuit or an overvoltage, then both vehicle electrical systems  102 ,  104  are separated from it and may continue to operate until batteries  108 ,  110  are drained. Consumer R 2   152 , which represents a consumer of average safety relevance, can thus still be supplied until both vehicle electrical subsystems  102 ,  104  have failed. 
         [0035]    Instead of diodes D 2   a    140  and D 2   b    142 , it is also possible to use intelligent switches that have a diode function. If generator  106  fails in such a case, then the driver should be warned that his or her vehicle or safety-related systems might fail in the foreseeable future. In the event of a battery short circuit, affected battery  108  or  110  is separated from consumer R 2   152  via corresponding diode  140  or  142 , and generator  106  is likewise separated from battery  108  or  110  via intelligent switch unit  120  or  130 . Consumer R 2   152 , having an average safety relevance, can continue to be supplied via other battery  108  or  110 . During the operation, consumer R 3   a    150  without safety relevance is supplied from first vehicle electrical subsystem  102 , and consumer R 3   b    154  without safety relevance is supplied from second vehicle electrical subsystem  104 . 
         [0036]    To simplify matters, it is also possible to omit the second battery. An example of such a topology including a generator and a battery is illustrate in  FIG. 3 .  FIG. 3  shows a vehicle electrical system  200 . 
         [0037]    In this case, a vehicle electrical subsystem made up of generator and consumer could be indicated in the event of a failure of the battery, and a vehicle electrical subsystem made up of battery and consumer could be indicated in the event of a failure of the generator. 
         [0038]    The illustration shows a generator  206 , a battery  208 , a first switch  210  parallel to a first diode D 1   212 , a switch unit  220  having a switch S 1   222  and a diode  224 , a switch S 2   226  in series with a second diode  228 , a switch S 3   230  as well as a consumer R 2   240  of average safety relevance, a consumer R 3   a    242  with no safety relevance, and a consumer R 3   b    244  with no safety relevance. 
         [0039]    In this specific example embodiment, consumer R 2   240  having an average safety relevance may be supplied either by way of generator  206  or battery  208  in the event that the other component fails. Generator  206  may fail both with a short circuit and an overvoltage. Vehicle electrical system  200  is effectively shielded from such a failure via switch S 1   222  or switch S 2   226 . A battery, in this case battery  206 , exhibits no overvoltage. As a result, only the short circuit of battery  208  is separated from vehicle electrical system  200  via diode D 1   212 . 
         [0040]    However, in this case it should be taken into account that with a non-available battery  208 , its buffer effect is lost as well. Consumers that draw steep and high power pulses from vehicle electrical system  200  are therefore unable to be supplied or can be supplied only with derating, i.e., choking. Provided battery  208  exhibits no short circuit, and parallel first switch  210  enables charging also via energy currents from vehicle electrical system  200 , e.g., during braking of electrical drives. 
         [0041]    If a consumer without safety relevance, in this case consumer R 3   a    242  or consumer R 3   b    244 , causes a short circuit or an overvoltage, such an event is kept away from consumer R 2   240  by switch S 3   230  opening. Switch unit  220  between battery  208  and generator  206  prevents that a short circuit of generator  206  or battery  208  also short-circuits the respective other component, and enables charging of battery  208  by generator  206 . 
         [0042]    In the illustrated specific example embodiments of  FIGS. 1 through 3 , switches are therefore provided by which back-and-forth switching between the two vehicle electrical subsystems is possible for consumer R 2  with an the average safety classification. In addition, switches are provided that make it possible to separate vehicle electrical subsystems, energy supplies, i.e., battery and/or generator, and/or consumers from the vehicle electrical system.