DE102006017921A1 - Motor vehicle`s electrical system operating method, involves assigning charging and discharging activities of super capacitor to areas for momentary voltage that are separated from one another through area boundaries - Google Patents

Abstract

The method involves connecting a secondary system parallel to a primary system and coupling a super capacitor with a bi-directional direct current/direct current (DC/DC) converter. A supercondenser is supercharged with a momentary voltage. Areas for the momentary voltage are separated from one another through area boundaries. Charging and discharging activities of a super capacitor are assigned to the areas, where the area boundaries are varied based on a vehicle and/or environment parameter. An independent claim is also included for an electrical system of a motor vehicle.

Description

The The present invention relates to a method for operating a Vehicle electrical system of a motor vehicle, wherein the electrical system is a primary system comprising a generator, an on-board battery and at least having a load in parallel, and a secondary system, that to the primary system is connected in parallel and one with a bidirectional DC / DC converter coupled supercapacitor and a control device for control of the DC / DC converter, wherein the supercapacitor on a momentary voltage is charged. It also relates to a corresponding On-board network of a motor vehicle.

Such, in 1 illustrated electrical system is known for example from the EP 1 013 506 A2 , Here is the electrical system 10 a motor vehicle, not shown, in a primary system 20 and a secondary system 30 divided. The primary system 20 comprises a driven by the engine of the vehicle generator G, which is connected to a load L and a vehicle electrical system battery B. In the load L all consumers are summarized in the vehicle.

The secondary system 30 comprises a DC / DC converter W and a supercapacitor K connected thereto. A terminal A1 of the DC / DC converter W is connected to the positive pole of the primary system 20 connected. The port A2 is of the DC / DC converter W connected via a line L1 to one pole of the supercapacitor K The voltage applied to the super capacitor voltage K is denoted by U _K. The other pole of the supercapacitor K is grounded. Both terminals of the DC / DC converter, A1 and A2, are each connected via lines LUB and LUK to a control unit S. The control unit S is further connected via a signal and / or control line L2 to the generator G. This line is shown in dashed lines, because it is not necessarily needed. In conventional generators, this is the so-called DF output. To control the DC / DC converter W is a control line S1, which leads from the controller S to the DC / DC converter W.

For operation: In the control unit S, a distinction between push and pull operation of the internal combustion engine is possible. The information signals necessary for this purpose are provided by an engine control unit (not shown) connected to the control unit S, however. If the motor vehicle is in overrun mode, then the DC / DC converter W is controlled in such a way that the supercapacitor K is charged. For this purpose, the output voltage U _{K of} the DC / DC converter is adjusted accordingly. The electrical energy stored in the supercapacitor K can be delivered independently of the state of charge of the supercapacitor K by appropriate control of the voltage U _{B present} at the terminal A1. In particular, in phases in which the generator G can not provide the entire energy supply of the electrical system, the DC / DC converter W is so controlled by the controller S that the supercapacitor K is discharged. As a result, a load on the vehicle electrical system battery B is largely prevented. The utilization of the generator G is detected in the control unit S via the signal applied to the line L2. If this line L2 does not exist, alternatively the utilization can be determined via the voltage U _B applied to the line LUB. In the cited prior art, it is further proposed to first charge the supercapacitor K at low temperatures after the engine has started, in order then to dispense the energy temporarily stored in the supercapacitor K at a later point in time onto the vehicle electrical system battery B warmed by the engine waste heat. Furthermore, it is proposed that the supercapacitor K always in the primary system 20 or to discharge into the battery B when the vehicle is stopped after an engine stop. Even if the internal combustion engine is in an unfavorable operating state with regard to efficiency and exhaust gas behavior, it is proposed to charge the supercapacitor K, since the additional load on the internal combustion engine can shift the operating point in the direction of an improved operating point. A comparable electrical system is known from the DE 103 13 081 A1 ,

The Object of the present invention is the initially mentioned Method for operating a vehicle electrical system or the aforementioned To further develop the electrical system in such a way that on the one hand a further fuel economy achieve, on the other hand, the life of the electrical system battery is increased.

These Task is solved by a method for operating a vehicle electrical system with the features of claim 1 and by an electrical system of a motor vehicle with the features of claim 14.

The present invention is based on the recognition that by means of an intelligent charging / discharging strategy relating to the supercapacitor a further fuel saving or a reduction in the charging cycles of the battery and thus an increase in the service life of the battery can be achieved. In this case, a distinction is made between at least three regions for the instantaneous voltage of the supercapacitor, which are separated from one another by a first range limit and by a second range limit. The at least three areas defined thereby are predefinable loading and / or unloading activities assigned to the supercapacitor. The stated advantages of the invention can be achieved by varying the range limits as a function of at least one vehicle and / or environmental parameter.

in the Prior art had a determination of the range limits in the In terms of priorities done, for the supercapacitor is used: highest priority here the starting process, the second priority is the afterflow, the third priority in fuel saving. The present invention now enables considering of vehicle and / or environmental parameters a change these priorities over a limited Time duration, d. H. above a period in which a higher Priority - with reference to a lower priority - according to experience not comes into consideration. This provides the opportunity for everyone Priority area over one, compared with the prior art, longer period or more often optimal to use.

A preferred embodiment is characterized by the fact that continues to have a third range limit which is also dependent on at least one vehicle and / or environmental parameters is varied.

A Variation of the range limits is dependent on at least one of following vehicle and / or environmental parameters: ambient temperature, Motor temperature, state of charge of the on-board battery, operation of one safety-critical consumer, operation of a high-current consumer, Vehicle speed, engine speed. Under safety-critical Consumers here are consumers to understand, in terms of their supply of energy highest priority enjoy, For example, the anti-lock braking system, a belt restraint system, an electronic Stability program, etc. High-current consumers are consumers who are themselves due to a high current consumption during operation and / or when switching on distinguished. These include, in particular, heaters such as Example, a rear window heating, a windscreen heater, a Seat heating, a heating of the passenger compartment, a catalyst heating, but also an electric steering, etc.

Accordingly, a first range is preferably defined within which the instantaneous voltage U _{K is} greater than or equal to the second range limit U ₂ , and if the instantaneous voltage is in this range, at least one activity for the first range is carried out. This is followed by a second range defined by: first range limit U1 <U _K <second range limit U2, where if U _{K is} in this range, at least one activity is performed for the second range. Finally, a third range is defined by U _K ≤ the first range limit U1, and if U _{K is} in the third range, at least one activity is performed for the third range.

Alternatively, a fourth region can also be provided, in which case the third region is defined by the third region boundary U0 ≦ U _K <first region boundary U1, and the fourth region by U _K <U0. If, therefore, third range limit U0 ≦ U _K <first range limit U1, at least one activity is performed for the third range and if U _K <third range limit U0, at least one activity for the fourth range.

The activities in the first region preferably comprise one or more of the following Activities: A charging of the supercapacitor in thrust or braking mode, and, if the engine is running and a condition is detected that indicates a lack of energy in the electrical system indicates a discharge of the supercapacitor in the electrical system.

The activities in the second region, preferably one or more of the following Activities: Charging the supercapacitor to at least the second range limit U2, if the engine is running in a speed range that has engine efficiency at least 90% of maximum vehicle-specific engine efficiency corresponds and / or during thrust or braking operation. A discharge of the Supercapacitor in the electrical system on the first range limit U1 or the third range limit U0 if the engine is off and a need by follow-up currents exists, taking under secondary flows the streams summarized, which serve to supply consumers, which are active in a parked vehicle, such as immobilizer, central locking, Clock, interior light, coming home light. (These can be about 10 amps for a duration of about 10 minutes.) A discharge of the supercapacitor up to the first range limit U1 in the electrical system, if the engine is on and a condition is detected that indicates a lack of energy in the electrical system indicates, or if the engine in a second speed range running, the engine efficiency of at most 90% of a maximum vehicle-specific Motor efficiency corresponds.

The activities in the third region preferably include one or more of the following activities: charging the supercapacitor to the first range limit U1 prior to starting the engine. A discharge of the supercapacitor for starting assistance at the start of the engine. Charging the supercapacitor to the first range limit U1 if the motor is running. Discharge of the supercapacitor into the vehicle electrical system in case the engine is running and a condition is detected that indicates a lack of energy in the vehicle Wiring system indicates. A charging of the supercapacitor from the electrical system, if the engine is running and a condition is detected, which indicates an excess of energy in the electrical system, in order to mitigate, in particular short-term, surges in the electrical system. Discharge of the supercapacitor into the on-board network up to the first range limit U1, if the engine is off and a demand is indicated by wake-up currents.

The activities in the fourth area preferably comprise one or more of the activities of third area, in which case the electrical system is a voltage converter, in particular a boost converter comprises.

The second range limit U2 is preferably raised if at least one of the following states is determined: drop in the ambient temperature below a specifiable limit value, state of charge of the vehicle electrical system battery falls below a predetermined limit, vehicle speed falls below a predefinable limit value, engine runs in a first speed range, the engine efficiency of at least 90% of a maximum vehicle-specific engine efficiency, turn on a high current consumer.

One Raising the second range limit U2 also has the advantage that the Charge of the supercapacitor with a better efficiency occurs. The higher the voltage range to which the supercapacitor is charged the lower is the necessary Current (P = U · I). Since the losses are proportional to the square of the charging current I, leads one Reduction of the charging current I to a significant reduction of Charging losses.

The second range limit U2 is preferably lowered, if at least one of the following states is determined: increase the ambient temperature over exceeds a predefinable limit value, state of charge of the vehicle electrical system battery exceeds a predefinable limit, vehicle speed a predefinable limit value, engine runs in a second speed range, the engine efficiency of at most 90% of a maximum vehicle-specific engine efficiency corresponds to switching off one High-current load. For example, one indicates over one specifiable limit lying vehicle speed, for example 80 km / h, indicating that not within the next 20 seconds the vehicle is turned off. Therefore, the reserved for caster streams Range can be reduced and in the sense of maximum fuel economy the Rekuperationsbereich be increased. Since a recuperation at voltages greater than the second range limit U2 is made, this is now by lowering the second Area limit U2. This allows for maximizing the for the Recuperation used area in the normal operation of the motor vehicle, whereby then the most fuel is saved. Nevertheless is through the intelligent solution according to this preferred embodiment the requirements for trailing streams Taking into account certain conditions of the vehicle or the environment, as mentioned above, be considered in the determination of the respective range limit U1, U2.

The first range limit U1 is preferably raised if at least one of the following states is determined: drop in the ambient temperature below a predefinable limit value, lowering of the engine temperature below a predefinable Limit. For example, it is known that batteries are not cold can absorb energy quickly enough. Will now be a vehicle operated in the winter in short-haul operation and also a heater from operated the vehicle battery, there is a risk of unloading the battery so that it may be over-discharged around for to provide enough energy to start up. The named preferred embodiment wear that Bill by the supercapacitor within the short drive times short-distance operation to an increased value of the first range limit U1 is charged, this energy after switching off the electrical system battery to disposal is provided. Keeping the range limit U1 constant without consideration the influence of the ambient temperature would become permanent here Discharge the battery and therefore from a certain point in time the starting process is no longer enable. An inherently high value the first range limit U1 while providing a certain reserve of energy for wake streams the recuperation, d. H. the range with voltages greater than or equal to the second range limit U2, restrict and thus to an increased Fuel consumption lead.

The first range limit U1 is preferably lowered, if at least one of the following states is determined: increase the ambient temperature over a predefinable limit, increase the engine temperature over a predefinable limit.

Further advantageous embodiments emerge from the dependent claims.

The with reference to the inventive method presented preferred embodiments and their advantages apply accordingly, as far as applicable, for the electrical system according to the invention of a motor vehicle.

in the Below will now be an embodiment of the invention with reference to the attached Drawings closer described. Show it:

1 in a schematic representation of a known from the prior art wiring system of a motor vehicle;

2 in schematic representation, different voltage ranges of a supercapacitor associated charging and discharging activities;

3 a representation of the losses when charging the supercapacitor as a function of the voltage at the supercapacitor.

2 shows a schematic representation of an exemplary selection of charging and discharging activities of a supercapacitor K as a function of four illustrated regions of the voltage U _{K of} the supercapacitor K. The left side shows each charging activities, the right side discharge activities. Below the range limit U0, which is preferably between 10 and 12 V, the supercapacitor K can only be used to a limited extent. Use is especially considered when the DC / DC converter W, see 1 , an up-conversion allows, for example by implementation as a boost converter.

First, to the charging activities: between the range U0 and U1, the supercapacitor is charged from the electrical system. Between the range U2 and U1, the supercapacitor is slowly charged from the vehicle electrical system when the engine is running, or quickly when recuperation in Schubbetreb. Between the voltage U _Kmax , which corresponds to the maximum voltage to which the supercapacitor K can be charged, and the voltage range U2, the supercapacitor is charged during recuperation in overrun mode.

About Discharge Activities: Between U1 and U0, the supercapacitor is discharged to the startup assistance, thereby relieving the battery. Between the range limit U2 and U1, the charge of the supercapacitor is used for follow-up currents and for on-board network stabilization, which also leads to a discharge of the battery. Finally, in the area between U _Kmax and U2, the charge of the supercapacitor is used for an energy supply to the vehicle electrical system and to the on-board network stabilization.

• – Umgebungstemperatur;
• – Motortemperatur;
• – Ladezustand der Bordnetzbatterie;
• – Betrieb eines sicherheitskritischen Verbrauchers;
• – Betrieb eines Hochstromverbrauchers;
• – Fahrzeuggeschwindigkeit;
• – Motordrehzahl.

As indicated by the double arrows, the range limits U0, U1 and U2 are not fixed but may be varied depending on at least one of the following vehicle and / or environmental parameters:

• - ambient temperature;
• - engine temperature;
• - state of charge of the vehicle electrical system battery;
• - operation of a safety-critical consumer;
• - operation of a high current consumer;
• - vehicle speed;
• - engine speed.

• – Absinken der Umgebungstemperatur unter einen vorgebbaren Grenzwert;
• – Ladezustand der Bordnetzbatterie unterschreitet einen vorgebbaren Grenzwert;
• – Fahrzeuggeschwindigkeit unterschreitet einen vorgebbaren Grenzwert;
• – Motor läuft in einem zweiten Drehzahlbereich, der einem Motorwirkungsgrad von mindestens 90 % eines maximalen fahrzeugspezifischen Motorwirkungsgrads entspricht; und
• – Einschalten eines Hochstromverbrauchers.

The second range limit U2 is preferably raised when at least one of the following conditions is detected:

• - Lowering the ambient temperature below a predefinable limit;
• - State of charge of the vehicle electrical system battery falls below a specifiable limit value;
• - Vehicle speed falls below a predefinable limit;
• The engine is operating in a second range of speeds corresponding to engine efficiency of at least 90% of maximum vehicle-specific engine efficiency; and
• - switching on a high current consumer.

• – Erhöhung der Umgebungstemperatur über einen vorgebbaren Grenzwert;
• – Ladezustand der Bordnetztemperatur überschreitet einen vorgebbaren Grenzwert;
• – Fahrzeuggeschwindigkeit überschreitet einen vorgebbaren Grenzwert;
• – Motor läuft in einem zweiten Drehzahlbereich, der einem Motorwirkungsgrad von höchstens 90 % eines maximalen fahrzeugspezifischen Motorwirkungsgrads entspricht;
• – Abschalten eines Hochstromverbrauchers.

In particular, the second range limit U2 is lowered when at least one of the following conditions is detected:

• - Increase of the ambient temperature over a predefinable limit value;
• - State of charge of the vehicle electrical system temperature exceeds a specifiable limit value;
• - Vehicle speed exceeds a predefinable limit value;
• The engine is running in a second speed range corresponding to engine efficiency of at most 90% of maximum vehicle-specific engine efficiency;
• - Switching off a high current consumer.

• – Absinken der Umgebungstemperatur unter einen vorgebbaren Grenzwert;
• – Absinken der Motortemperatur unter einen vorgebbaren Grenzwert.

The first range limit U1 is raised when at least one of the following conditions is detected:

• - Lowering the ambient temperature below a predefinable limit;
• - Lowering the motor temperature below a predefinable limit.

• – Erhöhung der Umgebungstemperatur über einen vorgebbaren Grenzwert;
• – Erhöhung der Motortemperatur über einen vorgebbaren Grenzwert.

The first range limit U1 is lowered, in particular if at least one of the following states is detected:

• - Increase of the ambient temperature over a predefinable limit value;
• - Increasing the motor temperature over a predefinable limit.

3 shows the dependence of the losses P _UK when charging the supercapacitor K as a function of the voltage U _K , to which the supercapacitor K is charged, for one embodiment. As you can clearly see, the losses go down with one almost quadratic dependence on a voltage rise U _K. An example selected value provides a power loss of 139 W at a voltage U _K of 24 V.

Claims (14)

Method for operating a vehicle electrical system ( 10 ) of a motor vehicle, the on-board network ( 10 ) a primary system ( 20 ) comprising a generator (G), a vehicle electrical system battery (B) and at least one consumer (L) connected in parallel, and a secondary system ( 30 ), which is the primary system ( 20 ) is connected in parallel and comprises a supercapacitor (K) coupled to a bidirectional DC / DC converter (W) and a control device (S) for controlling the DC / DC converter (W), the supercapacitor (K) being connected to the instantaneous Voltage (U _K ) is charged, characterized in that at least three areas for the instantaneous voltage (U _K ) are distinguished by a first area boundary (U1) and by a second area boundary (U2) are separated from each other, the at least three Areas are assigned to predetermined charge and / or discharge of the supercapacitor (K), wherein the first (U1) and the second range limit (U2) depending on at least one vehicle and / or environmental parameters are varied. Method according to claim 1, characterized in that that a third range limit (U0) is used, which depends on at least one vehicle and / or environmental parameter is varied. Method according to claim 1 or 2, characterized that the first range limit (U1), the second range limit (U2) and the third range limit (U0) depending on at least one of following vehicle and / or environmental parameters are varied: - ambient temperature; - engine temperature; - State of charge the electrical system battery; - Business a safety-critical consumer; - operation of a high current consumer; - vehicle speed; - engine speed. A method according to claim 1, characterized in that a) a first region is defined by U _K ≥ U2, wherein, if U _{K is} in the first region, at least one activity is performed for the first region; b) a second region is defined by U1 <U _K <U2, wherein if U _{K is} in the second region, at least one activity is performed for the second region; c) a third region is defined by U _K ≤ U1, wherein if U _{K is} in the third region, at least one activity is performed for the third region. A method according to claim 4, characterized in that the third region is defined by: U 0 ≤ U _K <U1, wherein a fourth region is defined by U _K <U0 wherein c1) if U 0 ≤ U _K <U1, at least one activity for the third area is executed; c2) if U _K <U 0, at least one activity for the fourth range is performed. Method according to one of claims 4 or 5, characterized in that the activities in the first region comprise one or more of the following activities: - in overrun or braking operation: charging the supercapacitor (K); - if the engine is running and a condition is detected that indicates a lack of energy in the electrical system ( 10 ): Discharge of the supercapacitor (K) into the electrical system ( 10 ). Method according to one of claims 4 to 6, characterized in that the activities in the second region comprises one or more of the following activities: - if the engine is running in a first speed range, which corresponds to a motor efficiency of at least 90% of a maximum vehicle-specific engine efficiency, and / or in the case of push or brake operation: charging the supercapacitor (K) to at least the second range limit (U2); - if the engine is off and there is a need for wake-up currents: discharge the supercapacitor (K) into the vehicle electrical system ( 10 ) except for the first range limit (U1) or the third range limit (U0); - if the engine is on and a condition is detected that indicates a lack of energy in the electrical system ( 10 ), or if the engine is running in a second speed range, which corresponds to a motor efficiency of at most 90% of a maximum vehicle-specific engine efficiency: unloading the supercapacitor (K) to the first range limit (U1) in the electrical system ( 10 ). Method according to one of claims 4 to 7, characterized in that the activities in the third region comprise one or more of the following activities: - before starting the engine: charging the supercapacitor (K) to the first range limit (U1); - when starting the engine: discharge of the supercapacitor (K) to the start support; - if the engine is running: charging the supercapacitor (K) to the first range limit (U1); - if the engine is running and a condition is detected that indicates a lack of energy in the electrical system ( 10 ): Discharge of the supercapacitor (K) into the electrical system ( 10 ); - if the engine is running and a condition is detected that is due to an excess of energy in the electrical system ( 10 ) indicates: charging the supercapacitor (K) from the electrical system ( 10 ); - if the engine is off and there is a need for wake-up currents: discharge the supercapacitor (K) into the vehicle electrical system ( 10 ) except for the first range limit (U1). Method according to one of claims 5 to 8, characterized in that the activities in the fourth area comprise one or more of the activities of the third area, the on-board network ( 10 ) comprises a voltage converter, in particular a step-up converter. Method according to claim 3, characterized, that the second range limit (U2) is raised if at least one the following states becomes: - sink the ambient temperature below a predefinable limit; - State of charge the vehicle electrical system battery falls below a specifiable limit value; - Vehicle speed falls below a predefinable limit; - Engine runs in a first speed range, the engine efficiency of at least Corresponds to 90% of maximum vehicle-specific engine efficiency; - Turn on a high current consumer. Method according to claim 3, characterized, that the second range limit (U2) is lowered if at least one the following states is detected: - increase of Ambient temperature over a predefinable limit value; - Charge state of the on-board battery exceeds a predefinable limit value; - Vehicle speed exceeds a predefinable limit value; - Engine is running in a second speed range, the engine efficiency of at most 90% of a maximum vehicle-specific engine efficiency corresponds; - Switch off a high current consumer. Method according to claim 3, characterized, that the first range limit (U1) is raised if at least one the following states is detected: - sink the ambient temperature below a predefinable limit; - sink the engine temperature below a predefinable limit. Method according to claim 3, characterized, that the first range limit (U1) is lowered if at least one the following states is detected: - increase of Ambient temperature over a predefinable limit value; - Increasing the engine temperature via a predefinable limit. Electrical system ( 10 ) of a motor vehicle, the on-board network ( 10 ) a primary system ( 20 ) comprising a generator (G), a vehicle electrical system battery (B) and at least one consumer (L) connected in parallel, and a secondary system ( 30 ), which is the primary system ( 20 ) is connected in parallel and comprises a supercapacitor (K) coupled to a bidirectional DC / DC converter (W) and a control device (S) for controlling the DC / DC converter (W), the supercapacitor (K) being connected to the instantaneous Voltage (U _K ) is charged, characterized in that at least three areas for the instantaneous voltage (U _K ) are defined, which are separated by a first area boundary (U1) and by a second area boundary (U2), wherein the at least three Areas are assigned to predetermined charge and / or discharge of the supercapacitor (K), wherein the first (U1) and the second range limit (U2) in dependence of at least one vehicle and / or environmental parameters are variable.