Electrical system for a vehicle

Abstract

A vehicle electrical system for a vehicle is described which includes an electrical energy source supplying a first vehicle electrical system branch and a second vehicle electrical system branch. The first vehicle electrical system branch include a first electrical consumer with an inrush current requirement and a first inductance connected in series with the first consumer. The second vehicle electrical system branch includes a second electrical system voltage-sensitive consumer with a minimum system voltage requirement and a second inductance connected to the second consumer in series or in parallel. The first vehicle electrical system branch and the second vehicle electrical system branch are connected electrically in parallel to one another, and the first inductance and the second inductance are magnetically coupled to one another.

Claims

1. A vehicle electrical system comprising: an electrical energy source; a first vehicle electrical system branch electrically connected to the electrical energy source and having at least one first electrical consumer with an inrush current requirement and a first inductance connected in series with the first electrical consumer; a second vehicle electrical system branch electrically connected to the electrical energy source and having at least one second electrical consumer and a second inductance which is connected in series or parallel with the second electrical consumer, wherein the second electrical consumer is voltage-sensitive having a minimum system voltage requirement; wherein the first vehicle electrical system branch and the second vehicle electrical system branch are connected in parallel with one another, and wherein the first inductance and the second inductance are magnetically coupled to one another.

2. The vehicle electrical system according to claim 1, wherein the second inductance is connected in series with the second consumer.

3. The vehicle electrical system according to claim 1, wherein the electrical energy source comprises an electrical energy storage unit.

4. The vehicle electrical system according to claim 1, further comprising; a primary winding associated with the first inductance between a first supply line and the first consumer; and a secondary winding associated with the second inductance between a second supply line to the second consumer.

5. The vehicle electrical system according to claim 4, wherein a number of windings of the primary winding is lower than a number of windings of the secondary winding.

6. The vehicle electrical system according to claim 4, further comprising a common magnetic core for the first and second inductances.

7. The vehicle electrical system according to claim 1, wherein the first inductance and the second inductance are magnetically coupled to one another in an anti-parallel manner.

8. The vehicle electrical system according to claim 1 further comprising: a coupling circuit arranged in parallel with the second consumer and electrical energy source, the coupling circuit having a discharge circuit including a first system node connecting the electrical energy source to the discharge circuit between the second inductance and the electrical energy source, and a second system node connecting the second consumer the discharge circuit; wherein the first inductance and the second inductance are coupled magnetically in parallel to one another and the second vehicle electrical system branch; and wherein the energy storage element counteracts the system voltage drop in the case of a system voltage drop.

9. The vehicle electrical system according to claim 8, further comprising a switching pulse generator operably coupled to the discharge circuit of the coupling circuit in the second vehicle electrical system branch for interaction therewith.

10. The vehicle electrical system according to claim 1, wherein the first consumer in the first vehicle electrical system branch is an electric starter motor of an internal combustion engine.

11. The vehicle electrical system according to claim 1, wherein the second consumer in the second vehicle electrical system branch is a system voltage-sensitive control unit.

12. The vehicle electrical system according to claim 1, wherein the second consumer in the second vehicle electrical system branch is a system voltage-sensitive ESP module, ECU-module or an automatic transmission control module.

13. A vehicle in combination with the vehicle electrical system according to claim 1.

14. The vehicle according to claim 13, wherein the vehicle comprises a start/stop system operable for automatically starting and stopping an internal combustion engine of the vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and:

(2) FIG. 1 shows a schematic representation of a vehicle with consumers in a vehicle electrical system;

(3) FIG. 2 shows a diagram of a vehicle electrical system according to a first embodiment in accordance with the present disclosure;

(4) FIG. 3 shows a diagram of a vehicle electrical system according to a second embodiment; and

(5) FIG. 4 exemplarily shows a diagram with voltage and current profiles in a vehicle electrical system during the switching-on of a starter motor during the first 100 milliseconds.

DETAILED DESCRIPTION

(6) The following detailed description is merely exemplary in nature and is not intended to limit the present disclosure or the application and uses of the present disclosure. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.

(7) FIG. 1 shows a schematic representation of a vehicle 40 in the form of a motor vehicle with consumers 3 and 6 in a vehicle electrical system 20. The vehicle electrical system 20 includes a first vehicle electrical system branch 2 and a second vehicle electrical system branch 5. In the first vehicle electrical system branch 2 a starter motor 19 as a first consumer 3 is arranged, which for example in a start/stop mode starts an internal combustion engine 22 with the help of a start/stop system 23. Such a starter motor 19 has a high inrush current requirement in the first milliseconds, which can amount to several hundred compares. The vehicle electrical system 20 with its two electrical system branches 2 and 5 is supplied with current and voltage from an electrical energy source in the form of an electrical energy storage unit 1.

(8) With each starting operation, a drop of the voltage in the vehicle electrical system branches 2 and 5 occurs through the high inrush current increase of several 100 amperes per millisecond for the starter motor 19. In order to counteract this drop in the vehicle electrical system branches 2 and 5, a first inductance 4 is arranged in the vehicle electrical system branch 2 in series with the first consumer 3, which via a magnetic core 12 is coupled to a second inductance 7, which is arranged in the second vehicle electrical system branch 5 in series with a second consumer 6.

(9) Such a second consumer 6 in this embodiment is a control unit 21 with a microprocessor. Such microprocessors are system voltage sensitive and have a minimum vehicle system voltage requirement, such as for example 7V, which should not be undershot in order to ensure the functionality of the control unit 21 despite multiple start/stop operation of the vehicle 40.

(10) Through the anti-parallel magnetic coupling of the first inductance 4 to the second inductance 7 indicated here with dots, the high current increase in the first vehicle electrical system branch 2 of several hundred volts per millisecond generates an induction voltage in the second inductance 7 of the second vehicle electrical system branch 5, which counteracts and thereby cushions the dropping of the vehicle electrical system voltage in the vehicle electrical system branch 5. While in FIG. 1 the interaction of internal combustion engine 22, energy storage unit 1, starter motor 19 and start/stop system 23 in the vehicle electrical system branch 2 is schematically shown in principle, a diagram of a vehicle electrical system 20 according to a first embodiment of the invention is shown by FIG. 2.

(11) In FIG. 2, the limits of the storage unit and of the individual branches of the vehicle electrical system are illustrated with the help of double-dotted interrupted lines. The vehicle electrical system 20, which in this case has a first vehicle electrical system branch 2, which is arranged in parallel with a second vehicle electrical system branch 5, is supplied by an electrochemical energy storage unit 1. The electrochemical energy storage unit 1 is connected to a vehicle electrical system voltage pole 17 and an earth pole 26, between which a vehicle electrical system voltage UB is formed.

(12) The schematically shown electrochemical energy storage unit 1 can generate via its complex internal resistance R.sub.i an inner source voltage U.sub.i of this vehicle electrical system voltage U.sub.b between the vehicle electrical system voltage pole 17 and the earth pole 26. However, through the complex internal resistance R.sub.i, which includes both ohmic as well as capacitive and inductive components, the vehicle electrical system voltage is not maintained in the case of a high increase of an inrush current.

(13) In order to counteract this voltage drop, the vehicle electrical system 20 in the embodiment according to FIG. 2 is divided into two parallel vehicle electrical system branches. In doing so, the first vehicle electrical system branch in addition to a first consumer 3 has a parallel branch with the starter motor 19, in which a starter relay 24 is arranged, which can be controlled by a start/stop system 23, wherein the starter relay 24 triggers a solenoid switch 25 which is closed in series, which is likewise part of the automatic start/stop system 23 and which connects the supply line 8 to the first consumer 3, the supply line 8 having a complex line resistance R.sub.L. The inductive component of the complex line resistance R.sub.L can be amplified by forming a primary winding 10 to a first inductance, which in the first vehicle electrical system branch 2 is arranged in series with the first consumer 3.

(14) Because of the high current, such a primary winding 10 can have a small number of windings, which is significantly lower than a second inductance 7, which is formed as secondary winding 11 of the supply line 9 to the second consumer 6 and has significantly more windings than the primary winding 10. Because of the high inrush current requirement in the first vehicle electrical system branch 2, an induction voltage is generated in the first vehicle electrical system branch 2 via magnetic coupling through a common magnetic core 12 in the secondary winding, which counteracts the lowering of the vehicle electrical system voltage.

(15) Thus, through this connection, it can be made possible that the vehicle electrical system voltage at least in the second vehicle electrical system branch 2 maintains a level which corresponds to the minimum vehicle electrical system requirement of the second consumer 6 of for example 7V with a nominal battery voltage of 12V. Nominal battery voltage U.sub.b in this connection is to mean a battery voltage that is exposed to a time-invariant constant load.

(16) FIG. 3 shows a diagram of a vehicle electrical system 30 according to a second embodiment of the invention. Components with same functions as in FIG. 2 are marked with the same reference characters and are not discussed separately. The electrochemical energy storage unit 1 is maintained unchanged and the first vehicle electrical system branch 2 is structured corresponding to FIG. 2. Merely the voltage supply in the second vehicle electrical system branch 5 was further improved by providing an additional coupling circuit 41. The coupling circuit 41 includes the second inductance 7, an additional energy storage element 13 in the form of a capacitor 27, a discharge circuit 15 and a first system node 14 and a second system node 18, with which the coupling circuit 41 is integrated in the second vehicle electrical system branch. With one connection, the second inductance is connected to the earth pole 26 via an electric line 42 and to the first system node 14 with a second connection. The additional energy storage element 13 is connected to the earth pole 26 with a first connection via an electrical line 43 and is connected to the first system node 14 with a second connection via the electrical line 44. The discharge circuit 15 is arranged between the first system node 14 and the second system node 18 and connected via the electrical lines 45 and 46 respectively.

(17) The second system node 18 is in connection with the second consumer and is connected to the vehicle electrical system voltage pole via an impedance element 16. Through the integration of this coupling circuit 41 into the second vehicle electrical system branch 5 an additional energy storage element 13 is available in this second vehicle electrical system branch 5, which in this case is formed by a capacitor 27, and which interacts with the second inductance via the first system node.

(18) This additional energy storage element 13 is able to make available the stored charge of the capacitor 27 to the second consumer 6 relatively quickly for offsetting a voltage drop in the second vehicle electrical system branch 4. The voltage drop is thus cushioned since the second consumer 6 in the form of a control unit 21 is connected to the additional energy storage element 13 via the second system node 18 in the second vehicle electrical system 5 and the discharge circuit 15.

(19) FIG. 4 shows a diagram with voltage and current profile in a vehicle electrical system during the switching-on of a starter motor during the first 100 milliseconds, which was obtained by means of a simulation. To this end, the time T in seconds is shown on the abscissa and on the left side of the ordinate the current i in ampere (A) and the rotational speed n in revolutions per minute (rpm) and on the ordinate on the right-hand side the voltage in volt (V) are plotted, wherein the voltage range is from zero to 14V and the current range is from zero to 1,200A.

(20) As the curve a shows, the rotational speed n of the starter motor increases from zero to 400 rpm in the first 100 milliseconds. A current of up to 1,000A is drawn from the first 6 milliseconds from the electrochemical energy storage unit for this, as is shown by curve b. Within the first 100 milliseconds, this inrush current of the starter motor drops to 400A. This steep inrush current increase from 1,000A per 6 milliseconds causes a drop in the battery voltage, as shown by the curve d, wherein the battery voltage of initially 12V drops to 8V within the first 6 milliseconds and then recovers to approximately 10V during the first 100 milliseconds.

(21) The voltage in the first vehicle electrical system branch, in which the steep current increase has the greatest effect, drops, as shown by the curve c, to far below 6V without the mentioned measures according to embodiments of the invention, as shown by FIG. 2, and remains below 7V for 8 milliseconds. This is not tolerable for some control units so that with the curve e it is shown how this voltage drop can be reduced in such a manner through the employed and magnetically coupled supply line inductances shown in the FIGS. 2 and 3 can be reduced in such a manner that a voltage of 7V within the circuit of the second consumer is not undershot.

(22) While exemplary embodiments have been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment is only an example, and are not intended to limit the scope, applicability, or configuration of the present disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the present disclosure as set forth in the appended claims and their legal equivalents.