METHOD FOR OPTIMISING THE POWER OF AN ELECTRIFIED VEHICLE, AND VEHICLE

Abstract

A method for optimising the power of an electrified vehicle having at least one electrical energy accumulator, at least one electrical drive and at least one auxiliary unit, the electrical energy accumulator having a maximum discharge power and a continuous discharge power. The power available from the electrical energy accumulator is distributed intelligently in order to make vehicle operation which is acceptable to the driver of the electrified vehicle possible.

Claims

1. A method for optimizing the power of an electrified vehicle, which includes at least one electrical energy accumulator, at least one electrical drive, and at least one auxiliary unit, the electrical energy accumulator having a maximum discharge power and a continuous discharge power, characterized in that the maximum discharge power is made available to the electrical drive and/or the at least one auxiliary unit in a certain energy contingent, the maximum discharge power is reduced to the continuous discharge power after the energy contingent is used up, and the power of the at least one auxiliary unit is reduced depending on the still available energy contingent of the maximum discharge power if a certain limit value is exceeded by the power demand for the electrical drive and the power of the at least one auxiliary unit.

2. The method according to claim 1, wherein the limit value is defined by the continuous discharge power of the electrical energy accumulator.

3. The method according to claim 1, wherein a certain ratio between the instantaneous discharge power of the electrical energy accumulator and the maximum discharge power of the electrical energy accumulator is selected as the limit value, preferably a ratio between 40% and 80%, particularly preferably a ratio between 50% and 70%.

4. The method according to claim 1, wherein the power of the at least one auxiliary unit is reduced depending on the temperature of the electrical energy accumulator.

5. The method according claim 1, wherein the power of the at least one auxiliary unit is reduced depending on the state of charge of the electrical energy accumulator.

6. The method claim 1, wherein at least two auxiliary units are provided, priorities are assigned to the auxiliary units, and the power of the auxiliary units is reduced depending on the assigned priority.

7. The method according to claim 6, wherein least one comfort system is supplied with power by an auxiliary unit, and a low priority is assigned to this auxiliary unit.

8. The method according to claim 1, wherein, upon dropping below a second limit value for the first time, after exceeding the limit value, the power of the at least one auxiliary unit is increased again.

9. The method according to claim 1, wherein the electrical energy accumulator is heated if the temperature of the electrical energy accumulator drops below a temperature limit value.

10. The method according to claim 1, wherein the instantaneous discharge power of the electrical energy accumulator is signaled to a driver of the electrified vehicle.

11. A vehicle, which includes at least one electrical energy accumulator, at least one electrical drive, at least one auxiliary unit, and at least one power control unit, the electrical energy accumulator having a maximum discharge power and a continuous discharge power, wherein the power control unit makes the maximum discharge power available to the electrical drive and/or the at least one auxiliary unit in a certain energy contingent, the power control unit reduces the maximum discharge power to the continuous discharge power after the energy contingent is used up, and the power control unit reduces the power of the at least one auxiliary unit depending on the still available energy contingent of the maximum discharge power if the power demand for the electrical drive and the power of the at least one auxiliary unit exceed a certain limit value.

12. The vehicle according to claim 11, wherein the electrical energy accumulator is a high-voltage battery.

13. The vehicle according to claim 11, wherein at least one heating element is provided for the electrical energy accumulator.

14. The vehicle according to claim 11, wherein at least one display device is provided, which has at least one display region for displaying the instantaneous discharge power of the electrical energy accumulator.

15. The vehicle according to claim 11, wherein the power control unit carries out a method.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0039] FIG. 1 shows a schematic representation of one exemplary embodiment of a vehicle according to the invention;

[0040] FIG. 2 schematically shows the relationship of individual parameters of a method according to the invention; and

[0041] FIG. 3 show an example of a profile of a performance indicator.

DETAILED DESCRIPTION

[0042] FIG. 1 shows an electrified vehicle 10, which includes an electrical energy accumulator 12 in the form of a high-voltage battery. Vehicle 10 includes two electrical drives 14, which are used for the locomotion of vehicle 10. Two auxiliary units 16 are also provided, which are understood to be auxiliary engines of vehicle 10. These auxiliary units 16 do not directly effectuate the locomotion of the vehicle, but rather supply power, for example to the electrical generator, which is not illustrated here. A maximum discharge power 18, a continuous discharge power 20, and an instantaneous discharge power 22 are assigned to electrical energy accumulator 12 (cf. FIG. 2). Electrical drive 14 and auxiliary units 16 are supplied with energy during the discharge of electrical energy accumulator 12.

[0043] A power control unit 24 is provided to optimize the power of electrified vehicle 10. If the performance of electrical energy accumulator 12 in vehicle 10 is not longer sufficient to adequately supply all auxiliary units 16 and fulfill the driver's request, i.e., the power for electric drive 14 requested by actuating the pedal for acceleration, a way must be found to intelligently distribute the available power to facilitate an acceptable vehicle operation for the driver.

[0044] In cold weather, in particular, if the power of the electrical energy accumulator is limited, due to the cold, a corresponding power management function which is carried out by power control unit 24 is advantageous.

[0045] For this purpose, it is provided that power control unit 24 performs a reduction and re-enabling of the power of auxiliary units 16 depending on instantaneous discharge power 22 of electrical energy accumulator 12. Vehicle control unit 24 ascertains how high instantaneous discharge power 22 is in relation to maximum discharge power 18 in the instantaneous operating state of electrical energy accumulator 12 according to the battery characteristic map of electrical energy accumulator 12 designed as a high-voltage battery. Maximum discharge power 18 in the instantaneous operating point of electrical energy accumulator 12 is available only in a certain time contingent. After the time contingent has been used up, maximum discharge power 18 is reduced to continuous discharge power 20. In the case of a high power demand above continuous discharge power 20, this takes place faster; with a moderate power demand above continuous discharge power 20, this takes place more slowly.

[0046] Due to a low cell temperature of electrical energy accumulator 12, and/or due to a low state of charge, continuous discharge power 20 may provide too little power for electrical drive 14 after deducting the power of auxiliary units 16 in order to adequately fulfill the driver's request. In the extreme case, continuous discharge power 20 is not sufficient to supply electric drive 14 and all auxiliary units 16 at the same time. To fulfill the driver's request as effectively as possible, power control unit 24 reduces the power for auxiliary units 16 depending on the still available contingent of maximum discharge power 18.

[0047] Before maximum discharge power 18 drops to continuous discharge power 20, a portion of the power of auxiliary units 16 has already been left out, and the power is available to electrical drive 14. In this way, a large portion of continuous discharge power 20 is always available for the drive. If a system recovering is detected by power control unit 24, the contingent for the demand of instantaneously maximum discharge power 18 is again increased. During the course thereof, a power enable takes place for auxiliary units 16 whose power was previously reduced. In this way, it remains ensured that the function of auxiliary units 16 does not cease entirely even in the case of greater power limitations of electrical energy accumulator 12. Auxiliary units 16 receive power if the driver does not request a lot of it for electrical drive 14.

[0048] The method carried out by power control unit 24 takes into account not only the general power limitation of electrical energy accumulator 12, for example due to a low cell temperature or a low state of charge, but explicitly also takes into account instantaneous discharge power 22, which results to a great extend from the driving actions performed by the driver. The method thus takes into account the instantaneous power demand by the driver in situations, in which vehicle 10 would have limited drivability, solely due to taking into account the limited system state of electric energy accumulator 12. The special feature is thus the redistribution of power between auxiliary units 16 and electrical drive 14. The crucial advantage consequently lies in a compromise, in which power is divided between auxiliary units 16 and electrical drive 14 in such a way that a preferably long and acceptable vehicle operation is possible, while simultaneously retaining some comfort systems, which are not illustrated here, despite the greatly limited power availability on the part of electrical energy accumulator 12.

[0049] Since maximum discharge power 18 of electrical energy accumulator 12 is highly temperature-dependent, and great losses in maximum discharge power 18 of electrical energy accumulator 12 are to be feared, particularly in cold weather, a heating element 26 for heating electrical energy accumulator 12 is provided to counteract a power drop. Heating element 26 is arranged in the immediate vicinity of electrical energy accumulator 12.

[0050] FIG. 2 graphically illustrates the method carried out by power control unit 24. The graphical representation may also be represented in a display region of a display device 28. A graphical representation, for example of instantaneous discharge power 22 or a profile of maximum discharge power 18, may provide the driver of vehicle 10 with pieces of information about the state of electrical energy accumulator 12. Due to the illustrated pieces of information, the driver may himself actively contribute to a power optimization, in that he adapts his mode of driving to the individual circumstances and, for example, does not request an excessive about of power from electrical drive 14 when maximum discharge power 18 approaches continuous discharge power 20.

[0051] An example of a profile of the power availability of electrical energy accumulator 12 is illustrated in FIG. 2. In the beginning, instantaneous discharge power 22 is briefly increased and subsequently drops back below continuous discharge power 20. This is followed by a phase, in which the maximum discharge power is requested, due to the interplay between the weather and the mode of driving of the driver of vehicle 10. Maximum discharge power 18 continuous to be requested until the time contingent for the use is consumed, and maximum discharge power 18 is reduced to continuous discharge power 20. This is apparent in the drop in maximum discharge power 18. To ensure the lifespan of electrical energy accumulator 12, maximum discharge power 18 is made available without limitation only for a maximum of 10 to 20 seconds, after which a reduction to continuous discharge power 20 takes place. The dashed line indicates maximum discharge power 18 if the time contingent for requesting maximum discharge power 18 were not used up.

[0052] Instantaneous discharge power 22 subsequently drops below continuous discharge power 20. The system recovers, and maximum discharge power 18 is again increased to its original value. The time contingent for using maximum discharge power 18 is also restored. So-called performance indicator 30, which is exampled in greater detail in FIG. 3, is illustrated in the lower diagram.

[0053] FIG. 3 shows the possibility for illustrating the method based on performance indicator 30. This type of representation is also possible on display device 28. Performance indicator 30 is indicated in percentage and supplies information about the availability and load-related limitation of maximum discharge power 18. In the case of a continuously low load below continuous discharge power 20, performance indicator 30 takes on the value 200%. If instantaneous discharge power 22 of electrical energy accumulator 12 is above continuous discharge power 20, the value continuously decreases in proportion to the amount of the excess. At 100%, the time contingent of maximum discharge power 18 is used up, and the active withdrawal of maximum discharge power 18 begins. Still available maximum discharge power 18 is scaled directly with unlimited maximum discharge power 18 via the value of performance indicator 30. If the load below continuous discharge power 20 is withdrawn, performance indicator 30 increases again.

[0054] If performance indicator 30 drops below an applicable threshold of 150%, the power of auxiliary units 16 is reduced from a higher power level to a lower one in proportion to performance indicator 30, down to a lower applicable threshold of 110% of performance indicator 30. If the power was only partially reduced, i.e., if performance indicator 30 has not dropped to 110%, power is again enabled only if performance indicator 30 exceeds a third applicable threshold of 180%. The higher power level is then enabled again on an ad-hoc basis. The applicable thresholds may also be adapted according to the requirements.

[0055] IN the range between 200% and 100%, maximum discharge power 18 of electrical energy accumulator 12 is available for a period of 30 seconds, or a lower power above the continuous discharge power is available for a correspondingly longer time. In the range between 100% and 0%, the available power is reduced from maximum discharge power 18 to continuous discharge power 20. A recovery takes place if power values of less than continuous discharge power 20 are requested.

[0056] In the exemplary embodiment described here, exactly two functions are reduced in power during the transition from the higher power level to the lower one. These are heating element 26 for heating electrical energy accumulator 12 and a base air conditioning system, which is not illustrated. If the lower power level is therefore reached, no power is available anymore to these two consumers. If the high power level is present, the two functions receive the power they request.

[0057] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.