DE102007037937A1 - Motor vehicle power supply system has power supply system branch with load and voltage source connected in parallel, and power supply system branch is coupled by direct current converter with former power supply system branch - Google Patents

Abstract

The motor vehicle power supply system has a power supply system branch (Branch1) with a load and a voltage source connected in parallel. Another power supply system branch (Branch2) is coupled by a direct current converter (DC-DC) with the former power supply system branch. Another load is coupled by a switchgear (S1,S2b,S2c) with the former power supply system branch or alternatively with the latter power supply system branch.

Description

The The invention relates to a motor vehicle electrical system.

By A motor vehicle electrical system will be various consumers with electrical Energy supplied. Consumers include "sensitive" consumers, their operation only at the highest possible and / or higher Tension is possible. On the other Side, there are "critical consumers", their use too short-term high energy requirements. "Critical" consumers, like the motor starter or the electric steering, as well as functions, like the Intelligent Generator Control (IGR), therefore, can significant dips and fluctuations in the voltage of the Create motor vehicle electrical system. In addition to the initial startup The engine after a stance phase are also engine starts during the driving operation, such as in hybrid vehicles with the Option of electric driving or after an MSA (engine start-stop Automatic) stop phase, conceivable. Fluctuations or burglaries The voltage in a motor vehicle electrical system can for Impairment or failure of the function more sensitive Consumers, such as an entertainment system lead. Such a functional failure or functional impairment is specific to certain sensitive consumers, especially during the Driving or the MSA stance phases intolerable.

The response of the generator (load response) is often throttled by a regulator under certain conditions, such as low engine speed (0 <N _engine <N _limit ), to reduce the torque feedback. The unthrottled response of the generator has a not negligible compared to the dynamics of the consumer in the electrical system inertia. Due to the inertia of the generator response, whether unthrottled or not, voltage dips due to load increases can not be compensated. Furthermore, this can, in particular with full and / or cold battery, critical voltage overshoots are generated due to load drops. An "unthrottled" generator response would affect the smoothness of the engine, especially at low speeds or idle due to load fluctuations in the electrical system.

By central measures, such as increasing capacity and performance of the battery (higher sizing), Although this would be a limitation of the voltage dips and - fluctuations in the motor vehicle electrical system as a result of Operation of critical consumers, both while driving as well as in stance phases (engine off) possible. A higher one However, dimensioning the battery leads to an increase vehicle weight and higher requirements the space requirement. In unfavorable conditions such as low temperature and bad condition of the battery itself would be one Measure no guarantee of undisturbed Operation of sensitive consumers.

By an adaptation of the generator dimensioning and control (more Performance, faster response) would also be a limitation the voltage dips and fluctuations during the Driving operation possible. An increase in generator dimensioning and adjusting its regulation does not lead to a reduction of voltage fluctuations and - burglary during the phases with the engine off (as with the MSA stop). Furthermore would be an increase in generator sizing and adapting its scheme to noticeable disturbing ones Torque effects on the engine lead (restless running).

Also by a sensitive consumers in the supply path upstream permanently operated voltage regulation stage, such as in DE 101 49 111 A1 or DE 100 19 847 A1 is described, the provision of a stable supply voltage would be possible. The use of such a voltage regulation stage ensures the stabilization of the supply of sensitive consumers but at the expense of a higher cumulative energy input. The losses in the voltage regulation stage are converted into heat, which can only be dissipated with a high technical outlay

By decoupling the critical consumers into separate buffered sub-networks, it is possible to relieve the base on-board network and limit voltage dips and voltage fluctuations ( DE 102 59 879 A1 ). However, such decoupling of the critical load requires additional energy storage with high capacity and performance and, where appropriate, electronic components for feeding such memory and consumers

Of the The present invention is therefore based on the object, a simple, in particular economically producible, motor vehicle electrical system with different, in particular "critical" and "sensitive", consumers through which consumers are energy efficient and reliable be supplied with the necessary electrical energy.

These The object is solved by the features of claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

One inventive motor vehicle electrical system has a first electrical system branch or wiring system area, which has a first, especially "critical", electrical consumers and one parallel to it connected voltage source, and a second On-board network branch or wiring system area, which has a second, in particular contains "sensitive" consumers and a third consumer. The term "consumer" is representative in the context of the invention for a consumer or a group of consumers.

moreover is a, in particular undirectional, DC-DC converter provided by the first electrical system branch coupled to the second electrical system branch is, in particular to the second electrical system branch with an opposite to supply the voltage in the first electrical system branch more stable voltage.

By a first switching device is the second consumer with the coupled to the first or the second electrical system branch. By a second Switching device is the third consumer with the first or coupled to the second electrical system branch.

Thereby can be the first and the second consumer depending from the needs of these consumers and depending from the current energetic conditions in the motor vehicle electrical system with the first electrical system branch or with the second electrical system branch be coupled.

Especially in the first electrical system branch, in addition to the first, in particular "critical", electrical consumer yet another, especially "insensitive" Consumers are included.

By a preferred parallel to the DC-DC converter switched third switching device, the DC-DC converter in the closed Switching state (the third switching device) bridged become. The first and second electrical system branch are then over the third switching device coupled together.

By the third switching device can therefore be the second electrical system branch even without the interposition of the DC-DC converter with energy be supplied. In particular, the second electrical system branch via the third switching device with inactive DC-DC converter niederimpendant be connected to the first electrical system branch. Thereby be electrical losses in a DC-DC converter occur, temporarily (with the third switching device closed) reduced or even avoided.

Preferably contains the second Bordnetzzweig an energy storage, In particular, a capacitor, by the first and second switching device switchable parallel to the second or third consumer or by the second or third consumer can be decoupled. This allows the Condenser as energy storage as needed the second or third consumer are connected or disconnected become. A node between the capacitor is preferred and the second and third switching means provided, with the the DC-DC converter in particular connected on the output side is.

Especially with closed third switching device can at appropriate energetic conditions, the voltage in the first electrical system branch supported by the voltage in the second electrical system branch or be stabilized. This is especially true with a fully charged capacitor possible.

According to one preferred development is a charging of the capacitor then prefers the DC-DC converter when the third Switching device is open.

Especially the invention is advantageous if it is the capacitor is a supercap or double-layer capacitor. At least it is for the temporary power supply of a second and / or third consumer in a motor vehicle electrical system advantageous if the capacity of the capacitor is greater than 50 millifarads.

The Voltage source (power source) preferably comprises a generator, a vehicle battery (rechargeable battery) and / or one, in particular via a further DC-DC converter, coupled to the motor vehicle electrical system High-voltage vehicle electrical system branch. In the latter case is in the motor vehicle electrical system (Low voltage onboard) a generator not required but possible.

The Invention is particularly advantageous in the context of a motor vehicle with a so-called engine start-stop system. It is the Motor of the motor vehicle automatically in a variety of vehicle standstill situations stopped and then restarted automatically. In known electrical systems leads the high power requirement of Motor starters during starting, especially when starting the Motors, regularly to voltage fluctuations in the Motor vehicle electrical system with negative effects on the rest Consumer. In particular, therefore, the first on-board network, especially as a "critical consumer" and / or first consumer, an engine starter, from which then the second and / or third consumer decoupled is.

Particularly preferred is a Steuereinrich tion, such as a processor device, provided for controlling the third shaft device, which, for example, programmatically set such that the third switching device during an engine start phase (for example, with the engine starter motor) in the open switching state, or that the third switching device in the open switching state is offset when the voltage falls below a predetermined limit in the first electrical system branch. The control device may also be part of the DC-DC converter.

Especially is doing the third switching device with (shortly before or shortly after that) the start of an engine start process (engine starter active) opened and / or with (shortly before or shortly thereafter) the Closed at the end of an engine start process.

alternative or in addition, the control device is for control the first switching device set such that during an engine start phase of the second consumer through the first switching device is coupled to the second electrical system branch, and / or that the second Consumer through the first switching device with the second electrical system branch is coupled, if in the first electrical system branch, the voltage below falls below a predetermined limit. Accordingly, preferably the first switching device with (shortly before or shortly thereafter) the Start of an engine start process (engine starter active) on the second electrical system branch switched and / or with (shortly before or shortly after that) the end of an engine start process on the first electrical system branch connected.

alternative or in addition, the control device is for control the second switching device configured such that during an engine start phase of the third consumer through the second switching device is coupled to the first electrical system branch, and / or that the third Consumer through the second switching device with the first electrical system branch is coupled, if in the first electrical system branch, the voltage below falls below a predetermined limit. Accordingly, preferably the second switching device with (shortly before or shortly thereafter) the Start of an engine start process (engine starter active) on the first electrical system branch switched and / or with (shortly before or shortly after that) the end of an engine start process on the second electrical system branch connected.

The Switching devices can also be indirect or immediate triggered by the command to start the engine or to deactivate it of the motor starter or triggered by the recognized incipient strong voltage dip or the recognized onset of voltage stabilization - such as just described - to be controlled.

embodiments The invention will be described in greater detail below with reference to drawings explained. Show it:

1 a simplified representation of a motor vehicle electrical system;

2 a representation of a state matrix;

3 an illustration of a state diagram;

4 a representation of the time course of the engine speed and associated electrical system states.

1 shows a motor vehicle electrical system with a first on-board network branch (branch 1) and a second board network branch (branch 2).

Of the first electrical system branch (branch 1) contains a first "critical" Consumers, like a motor starter S, another "insensitive" Consumer (consumer group A), an energy producer or energy supplier, such as a generator G, and optionally an energy storage ES1, such as a car battery, especially a battery.

Of the second electrical system branch (branch 2) contains a second "sensitive" Consumers (consumer group B), such as entertainment devices, and a third consumer (consumer group C), as well as one Energy storage ES2, such as a capacitor or a supercap.

Of the second consumer (consumer group B) can through the first switching device S2b, in particular a changeover switch, with the first electrical system branch or be coupled to the second electrical system branch. The third consumer (Consumer group C) can be detected by the second switching device S2c, in particular a changeover switch, also with the first electrical system branch or be coupled to the second electrical system branch.

The two electrical systems branches are by a DC-DC converter (DC) DC / DC coupled together, wherein the DC-DC converter DC / DC through the third switching device S1 can be bridged. The energy storage ES2 can by means of a DC-DC converter DC / DC or via the closed switch S1 from the first On-board network branch are loaded. The voltage U2 in the second electrical system branch can be regulated by the DC-DC converter DC / DC and / or with be buffered the energy storage ES2.

The switching devices S2b, S2c, S1 who controlled by a control device, not shown.

Of the Operation of the second consumer B (eg audio components, telephone, Displays, MOST scopes) can be subject to fluctuations and in particular Voltage drops in certain situations (eg when starting the engine). In such Situations, consumer group B is decoupled from branch 1 and fed in branch 2 with a stabilized voltage.

Of the third consumer C in this example also includes "sensitive" Consumers (eg indoor and outdoor light scopes), which is decoupled from branch 1 at another time and by branch 2 as the second consumer B.

alternative In addition, the third consumer C consumer with high transient Include power requirements ("transient interferers"), due to their load characteristics in certain operating conditions of the Vehicle (eg while driving) from the base board network (branch 1) decoupled and fed with a buffered voltage U2 in branch 2 should. Transient interferers include systems that which during the stance phase or during the startup process not mandatory need a stabilized supply (for example VVT, DSC or ABS).

Next The mentioned consumer groups can of course further consumer groups in the first and / or second on-board network branch be included, and on the said or other switching devices be coupled to the first and / or second electrical system branch.

in the The following is an operating strategy for the electrical system and in particular the switching devices S1, S2b and S2c an example explained in which the second consumer group B includes sensitive consumers, and the third consumer group comprises C transient interferers.

there is provided that with open switching device S1, the switchable Consumer groups B and C are fed selectively from branch 2 (eg only one consumer group at a time). The operating strategy for the switching devices S2b, S2c and the feeding device DC / DC is designed such that a consumer group decoupled and fed from branch 2, if the quality the voltage from branch 1 is not sufficiently guaranteed would be and / or the load characteristic of this consumer group affect the stability of the tension in branch 1 would.

The two electrical systems branches are by the switching device S1 only then connected (U1 = U2), if a sufficient voltage stability guaranteed for sensitive consumers throughout the vehicle electrical system and the characteristic of the "transient interferers" the on-board network stability not endangered.

In 2 a possible state matrix is shown, are assigned by which different operating conditions of a vehicle or the electrical system different switch positions of the switching devices or functions of the DC-DC converter DC / DC. In the "stand-by" state, the entire system is switched off. In the "charge / discharge" state, the state of charge of the energy store ES2 and the voltage U2 in the branch 2 are adapted to the voltage U1 or another desired target value by means of the feed device (DC / DC converter).

The States A, B and C correspond to regular operating conditions of the electrical system.

In state A, the switching device S1 is closed; both electrical systems branches are coupled by it. Both switchable consumer groups B, C are supplied in this case with U1 = U2 (s. 1 ).

in the State B, the switching device S1 is open. In state B will consumer group B (sensitive consumers) decoupled from branch 1 and fed with a stabilized voltage in branch 2. The consumer group C is decoupled from branch 2 and fed with the voltage from branch 1.

in the State C, the switching device S1 is also open. The consumer groups A and C are fed from branch 1. In state C becomes the consumer group C or the "transient interferers" from branch 1 decoupled and supplied by branch 2. Consumer group B (sensitive consumers) can then decoupled from branch 2 and with the tension in branch 1 are fed.

in the State B and C can be different voltages U1 and U2 be.

The state diagram in 3 shows an exemplary embodiment for the states of the electrical system with corresponding stimuli for the state transitions. N denotes the engine speed.

The system assumes state A when the engine is off (N _motor = 0) or when it is running at a high speed (above a defined threshold N _motor > N _limit > 0). As a result, in particular voltage dips in the state due to load fluctuations (generator off) and voltage overshoot due to the dynamic control behavior during load shedding are contained. The energy to feed consumers from the consumer A, B and C are taken directly from the base network (branch 1). The DC / DC converter transmits no energy.

State B is maintained for the duration of a sharp dip of U1 ( 1 ), for example as a result of an engine starting process. At the same time, the sensitive consumers are not experiencing a break in the supply voltage.

In the event that the engine is running at a speed 0 <N _motor <N _limit , the system is in state C ( 3 ). If, at 0 <N _motor <N _limit , the maximum generator output power is throttled and / or the response is restricted, in state C the on-board network is not loaded with the transient interferers. These are supplied from the buffered branch 2. The speed threshold N _limit can be carried out for the transitions from state A to state C and vice versa with a hysteresis. As a stimulus for the transition from state A to state C and vice versa, the speed threshold N _{limit can be} linked to another condition (eg temperature / state of charge of ES1).

Of the Energy storage ES2 buffers the load transients in the states B and C in branch 2. As a result, the DC / DC converter does not have the maximum but provide the average power to feed them.

An assignment of these electrical system states to vehicle / engine states is in 4 in the context of the representation of an exemplary engine speed curve over time.

• – an den Zustand des Fahrzeugs und die Energie-/Leistungsverfügbarkeit angepasste Lastverteilung;
• – Stabilisierung der sensiblen Verbraucher bei drastischen Einbrüchen der Bordnetzspannung wird ermöglicht;
• – die Spannung im Basisbordnetz kann durch das Zuschalten von ES2 sowohl im Stand als auch während der Fahrt stabilisiert werden (dadurch wird die Leistungsverfügbarkeit im gesamten Bordnetz gesteigert, der Primärenergiespeicher (ES1) entlastet, der Generator stetiger und somit effizienter geregelt werden);
• – die transienten Störer können vom Basisbordnetz entkoppelt werden, wenn die statische und dynamische Leistungsfähigkeit des Generators eingeschränkt ist (dadurch wird die Spannung im Basisbordnetz nicht destabilisiert, der Primärenergiespeicher (ES1) entlastet, der Generator stetiger und somit effizienter geregelt);
• – der DC/DC-Wandler wird für die selektive und nicht gesamtheitliche Speisung der schaltbaren Verbraucher ausgelegt (niedrigere Dimensionierung des DC/DC-Wandlers möglich);
• – beim Einsatz des Energiespeichers ES2 kann der DC/DC-Wandler mit Hinblick auf die durchschnittlich erforderliche Leistung zur Speisung der Verbrauchergruppe B oder C dimensioniert werden;
• – die Speisung der schaltbaren Verbraucher B und C erfolgt nur dann aus dem Zweig 2, wenn es die Betriebstrategie erfordert; im Übrigen werden eine, mehrere oder alle schaltbaren Verbrauchergruppen direkt aus dem Basisbordnetz gespeist, wodurch im DC/DC-Wandler keine Verluste entstehen;
• – bei Ausfall der Einspeisevorrichtung und/oder des Speichers ES2 existiert für die Speisung der schaltbaren Verbrauchergruppen mit der Speisung aus Zweig 1 ((S1 geschlossen) oder (S1 offen und erste und zweite Schalteinrichtung auf Zweig geschaltet)) eine Rückfalllösung.

By the invention or its developments, in particular the following advantages are achieved:

• - load distribution adapted to the condition of the vehicle and the energy / power availability;
• - Stabilization of sensitive consumers in case of drastic drops in the vehicle electrical system voltage is made possible;
• - the voltage in the base on-board network can be stabilized by connecting ES2 both while stationary and while driving (this increases the power availability in the entire on-board network, relieves the primary energy storage (ES1), the generator becomes more stable and thus more efficient);
• - the transient interferers can be decoupled from the base board network, if the static and dynamic performance of the generator is limited (thereby the voltage in the base board network is not destabilized, the primary energy storage (ES1) relieved, the generator more steadily and thus more efficiently controlled);
• - The DC / DC converter is designed for the selective and non-integral supply of the switchable consumers (lower dimensioning of the DC / DC converter possible);
• When using the energy storage device ES2, the DC / DC converter can be dimensioned to supply the consumer group B or C with regard to the average power required;
• - The supply of the switchable loads B and C takes place only from the branch 2, if it requires the operating strategy; Incidentally, one, several or all switchable consumer groups are fed directly from the base board network, resulting in the DC / DC converter no losses;
• - In case of failure of the feeder and / or the memory ES2 exists for the supply of switchable load groups with the supply of branch 1 ((S1 closed) or (S1 open and first and second switching device switched to branch)) a fallback solution.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10149111 A1 [0006]
• - DE 10019847 A1 [0006]
• - DE 10259879 A1 [0007]

Claims (11)

Motor vehicle electrical system - with a first electrical system branch, the first consumer (S) and a contains voltage source connected in parallel thereto, - With a second electrical system path, which by a DC-DC converter (DC / DC) can be coupled or coupled to the first vehicle electrical system branch, - With a second consumer (B) passing through a first switching device (S2b) with the first electrical system branch or alternatively with the second electrical system branch is coupled, and - with a third consumer by a second switching device (S2c) with the first electrical system branch or alternatively with the second On-board network branch can be coupled. Motor vehicle electrical system according to claim 1, - With a third parallel to the DC-DC converter (DC / DC) connected Switching device (S1), by the closed switching state the DC-DC converter (DC / DC) bridges becomes. Motor vehicle electrical system according to one of the preceding Claims, wherein the second electrical system branch a capacitor (ES2) provided by the first switching device (S2b) switchable parallel to the second consumer (B) or from the second Consumer is decoupled, and by the second switching device (S2c) switchable parallel to the third consumer (C) or of the third consumer is decoupled. Motor vehicle electrical system according to one of the preceding Claims with a node between the capacitor (ES2) and the first and / or second switching device (S2b, S2c), with which is connected to the DC-DC converter. Motor vehicle electrical system according to one of the preceding Claims in which the capacitor (ES2) via the DC-DC converter (DC / DC) can be charged and / or discharged is when the third switching device (S1) in the open Switching state is located. Motor vehicle electrical system according to one of the preceding Claims in which the capacitor comprises a supercap. Motor vehicle electrical system according to one of the preceding Claims in which the voltage source is a generator, a vehicle battery and / or one, in particular via another DC-DC converter (DC / DC) coupled, Hochvoltbordnetzzweig comprises or is formed thereby. Motor vehicle electrical system according to one of the preceding Claims in which the first on-board network branch, in particular as the first consumer that contains a motor starter. Motor vehicle electrical system according to one of the preceding Claims, with a control device for controlling the third switching device (S1), which is set up in such a way - that the third switching device (S1) during an engine start phase is in the open switching state, or - that the third switching device (S1) placed in the open switching state is, if in the first electrical system branch, the voltage below a predetermined limit falls Motor vehicle electrical system according to one of the preceding Claims, with a control device for controlling the first switching device (S2b) arranged such - that during an engine start phase, the second consumer through the first switching device (S2b) with the second electrical system branch coupled, and / or - that the second consumer coupled by the first switching device (S2b) with the second electrical system branch is, if in the first electrical system branch, the voltage below a predetermined Limit falls. Motor vehicle electrical system according to one of the preceding Claims, with a control device for controlling the second switching device (S2c) arranged such - that during an engine start phase, the third consumer through the second switching device (S2c) with the first electrical system branch coupled, and / or - that the third consumer by the second switching device (S2c) with the first vehicle electrical system branch is coupled, if in the first electrical system branch, the voltage below falls below a predetermined limit.