Method for providing a power supply for at least one electrically heatable catalyst of a motor vehicle situated in an exhaust gas tract, and a motor vehicle comprising at least one electrically heatable catalyst situated in an exhaust gas tract of the motor vehicle

Abstract

A method for providing a power supply for at least one electrically heatable catalyst of a motor vehicle situated in an exhaust gas tract, wherein the motor vehicle comprises a first battery, by means of which a first voltage U.sub.1 is generated, and a second battery, by way of which a second voltage U.sub.2 is generated, wherein the at least one catalyst during a start phase immediately following the start of an internal combustion engine of the motor vehicle is supplied by a power P.sub.1 provided by the first battery such that the voltage U.sub.1 of the first battery is imposed on the at least one catalyst, wherein the at least one catalyst is additionally supplied during the start phase by a power P.sub.2 provided by the second battery such that the voltage U.sub.2 of the second battery is transformed by a DC converter to the value of the voltage U.sub.1 which is imposed on the at least one catalyst.

Claims

1. A method for providing a power supply for at least one electrically heatable catalyst situated in an exhaust gas tract of a motor vehicle, comprising: generating a first voltage U1 using a first battery of the motor vehicle; generating a second voltage U2 using a second battery of the motor vehicle; during a start phase immediately following a start of an internal combustion engine of the motor vehicle, supplying the at least one electrically heatable catalyst with a first power P1 provided by the first battery such that the voltage U1 of the first battery is imposed on the at least one electrically heatable catalyst; and during the start phase, supplying the at least one electrically heatable catalyst with a second power P2 provided by the second battery such that the voltage U2 of the second battery is transformed by a DC converter to the voltage U1 which is imposed on the at least one electrically heatable catalyst; wherein the first battery only provides the power P1 in a particular region of its state of charge SoC, and this region is bounded by a lower value SoC0 and an upper value SoC1, wherein the lower value SoC0 is 25% and the upper value SoC1 is 80% of a maximum state of charge of the first battery, and energy EEHC consumed during the start phase of the at least one electrically heatable catalyst is apportioned between the first battery and the second battery such that, upon ending of the start phase, the state of charge SoC of the first battery corresponds at least to the lower value SoC0.

2. The method according to claim 1, wherein the at least one electrically heatable catalyst is supplied in addition by the power P2 provided by the second battery during the start phase only.

3. The method according to claim 1, wherein the at least one electrically heatable catalyst is also supplied by the power P2 provided by the second battery after the ending of the start phase.

4. A method for providing a power supply for at least one electrically heatable catalyst situated in an exhaust gas tract of a motor vehicle, comprising: generating a first voltage U1 using a first battery of the motor vehicle; generating a second voltage U2 using a second battery of the motor vehicle; during a start phase immediately following a start of an internal combustion engine of the motor vehicle, supplying the at least one electrically heatable catalyst with a first power P1 provided by the first battery such that the voltage U1 of the first battery is imposed on the at least one electrically heatable catalyst; and during the start phase, supplying the at least one electrically heatable catalyst with a second power P2 provided by the second battery such that the voltage U2 of the second battery is transformed by a DC converter to the voltage U1 which is imposed on the at least one electrically heatable catalyst; wherein the power P1 which can be provided by the first battery depends on its current state of charge SoC, while the energy EEHC consumed during the start phase by the at least one electrically heatable catalyst is apportioned between the first battery and the second battery such that, upon ending of the start phase, the power P1 which can be provided by the first battery corresponds at least to the power of the at least one electrically heatable catalyst which is required at this time.

5. The method according to claim 4, wherein a known characteristic curve and/or a lookup table and/or a model, is used to apportion the energy EEHC consumed during the start phase by the at least one electrically heatable catalyst between the first battery and the second battery, which describes the region of the state of charge SoC of the first battery in which it provides the power P1, and/or the dependency of the power P1 which can be provided by the first battery on its state of charge SoC, in temperature-dependent manner.

6. A method for providing a power supply for at least one electrically heatable catalyst situated in an exhaust gas tract of a motor vehicle, comprising: generating a first voltage U1 using a first battery of the motor vehicle; generating a second voltage U2 using a second battery of the motor vehicle; during a start phase immediately following a start of an internal combustion engine of the motor vehicle, supplying the at least one electrically heatable catalyst with a first power P1 provided by the first battery such that the voltage U1 of the first battery is imposed on the at least one electrically heatable catalyst; and during the start phase, supplying the at least one electrically heatable catalyst with a second power P2 provided by the second battery such that the voltage U2 of the second battery is transformed by a DC converter to the voltage U1 which is imposed on the at least one electrically heatable catalyst; wherein the energy EEHC transferred during the start phase and/or after the end of the start phase from the first battery and the second battery to the at least one electrically heatable catalyst is apportioned by a fixed or adjustable provision quotient Q between the first battery and the second battery; wherein the provision quotient is set with the help of at least one state of charge information item describing the state of charge SoC of the first battery and/or the state of charge SoC of the second battery, wherein the state of charge information is ascertained by at least one sensor of the motor vehicle and/or is present in the context of a controlling of the motor vehicle which can be done by a control unit.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) Further details and benefits emerge from the following schematic drawings as well as the described embodiments.

(2) FIG. 1 shows an energy balance diagram of a first battery of a motor vehicle.

(3) FIG. 2 shows a characteristic curve of a first battery of a motor vehicle.

(4) FIG. 3 shows a motor vehicle.

DETAILED DESCRIPTION

(5) While FIGS. 1 and 2, which will also be taken up later on, show the energy balance diagram 18 and the characteristic curve 14 already described in the introduction, FIG. 3 presents a schematic view of a motor vehicle 1, with the aid of which corresponding embodiments of the method will be explained.

(6) The motor vehicle 1 comprises an internal combustion engine 2 and an exhaust gas tract 3 connected to the internal combustion engine 2. The internal combustion engine 2 is a gasoline engine, for example. The exhaust gases produced by the internal combustion engine 2 are channeled into the exhaust gas tract 3, which comprises two exhaust gas channels 4, for example. In the region of the exhaust gas channels 4 there is arranged a respective electrically heatable catalyst 5 (EHC) as well as other components for the cleaning of the exhaust gas, such as further catalysts like oxidation and/or SCR catalysts, as well as particulate filers and/or the like, not otherwise represented. After passing through the exhaust gas tract 3, the exhaust gas goes across mufflers 6 into the surroundings 7 of the motor vehicle 1.

(7) For the power supply of the EHCs 5 there is a first battery 8, by means of which a first voltage U.sub.1 is generated, and a second battery 9, by means of which a second voltage U.sub.2 is generated. The first battery 8 serves furthermore for the power supply of a first onboard network 10 and the second battery 9 for the power supply of a second onboard network 11. For example, a voltage of U.sub.1=48 V can be generated by means of the first battery 8 and a voltage of U.sub.2=12 V by means of the second battery 9.

(8) A control mechanism 12 of the motor vehicle 1 is adapted to control the power supply of the EHC 5 by means of the first battery 8 and the second battery 9. Thus, the first battery 8, the second battery 9 and the EHCs are directly connected by means of an electrical circuit 19 such that they can be interconnected with each other by two possible circuit conditions, wherein the control mechanism 12 is adapted to send corresponding control commands to set the current circuit condition. The electrical circuit 19 is realized by means of components based on semiconductor technology, such as transistors or the like, which are actuated on the part of the control mechanism 12 by appropriate control signals. Details regarding circuits such as the circuit 19 are sufficiently known to the person skilled in the art and therefore will not be further explained.

(9) In a first circuit condition, the EHCs 5 are only energized by the first battery 8. In a second circuit condition, the EHCs 5 are additionally energized by the second battery 9. In the second circuit condition, the system composed of the first battery 8, the second battery 9 and the DC converter 13 works such that two parallel-switched voltage sources of identical voltage U.sub.1 are present on the EHCs 5, for their part switched in parallel, one of these voltage sources being the first battery 8 and the second of these voltage sources being formed so to speak by the second battery 9 and the DC converter 13. A switching between the first and the second circuit condition thus has the effect, in terms of the power supply of the EHCs 5, that either only the first battery 8 or the first battery 8 together with the second battery 9 is used, and in both circuit conditions the voltage U.sub.1 is present on each of the two EHCs.

(10) The method involves a start phase occurring immediately after the start of the internal combustion engine 2 and lasting for around 30 seconds. During this phase, the requirements for the EHCs 5 are particularly high. This is because the rate of production of pollutants of the internal combustion engine 2 is especially high during the start phase, as compared to other operating phases. During the start phase, the EHCs 5 are supplied on the one hand with a power P.sub.1 provided by the first battery 8. On the other hand, the voltage U.sub.2 of the second battery 9 is transformed during the start phase by means of a DC converter 13 to the value of the voltage U.sub.1 of the first battery 8, the EHCs 5 being additionally supplied by means of the power P.sub.2 provided by the second battery 9. In this case, the control mechanism 12 ensures that the EHCs are supplied with an adequate power during the entire start phase, for example with at least their known operating powers P.sub.EHC.

(11) In the motor vehicle shown in FIG. 3, the voltage U.sub.1 provided by means of the first battery 8 and the voltage U.sub.2 provided by the second battery 9 and transformed by means of the DC converter 13 to the value U.sub.1 are imposed directly on the two EHCs 5. Likewise, however, it may be provided that the voltage provided by the second battery 9 and transformed by means of the DC converter 13 is imposed on the first battery 8 and charges it. There is so to speak an indirect power supply of the EHCs 5 by means of the second battery 9, namely, across the first battery 8.

(12) In the embodiments which are explained with the aid of the figures, the specific aspects mentioned in the introduction and only to be understood as examples will be explicitly assumed, as long as they are not inconsistent with the present descriptions. Thus, it is provided that the first battery 8 is a 48V battery with an overall capacity E.sub.ges of 850 Wh and the two EHCs 5 each have a maximum operating power of 5 kW, so that the overall power required by the EHCs 5 is at most E.sub.EHC=10 kW.

(13) In the following, refer once again to FIG. 2. As already explained, this characteristic curve 14 pertains to the first battery 8, the abscissa 15 or x-axis referring to the state of charge SoC of the first battery 8 in percent and the ordinate 16 or y-axis referring to the power P.sub.1 in kW which can be provided by the first battery 8. It is seen from the characteristic curve 14 that a power P.sub.1 can only be provided by means of the first battery 8 in a certain region of its state of charge SoC, this region being bounded for example by a lower value of SoC.sub.0=25% and an upper value of SoC.sub.1=80%. Furthermore, the characteristic curve 14 shows that the power P.sub.1 which can be provided by the first battery 8 is dependent on the current state of charge SoC of the first battery 8. The power P.sub.1 which can be provided by means of the first battery 8 depends furthermore on the current temperature, the characteristic curve 14 represented in FIG. 2 being plotted at a temperature of −10° C. Thus, multiple characteristic curves 14 or corresponding numerical values each pertaining to a temperature value are saved in the control mechanism 12, especially in the context of a lookup table or an analytical model. The control mechanism 12 is adapted to select the particular characteristic curve 14 in dependence on a metered value of a temperature sensor 17 describing the current temperature. The temperature sensor 17 meters either the current temperature in the surroundings 7 of the motor vehicle 1 or the immediate temperature of the first battery 8.

(14) Thus, it shall first be assumed in one embodiment of the method that the state of charge of the first battery 8 does not fall below the value of SoC.sub.0=25% during the entire start phase and that this value should be present at the end of the start phase. It follows from the characteristic curve 14 presented in FIG. 2 that the power P.sub.1 which can be provided by the first battery 8 at the end of the start phase, which SoC is supposed to be SoC.sub.0=25%, corresponds to around 5 kW. Assuming that the power required by the EHCs at this time is P.sub.EHC=10 kW, there necessarily results a corresponding power demand on the part of the second battery 9 of P.sub.2=5 kW. Due to the circumstance that the first battery 8 can provide a power P.sub.1 only at a state of charge of SoC≥25%, it further emerges that the EHCs 5 also need to be supplied at the end of the start phase in addition by means of the power P.sub.2 provided by the second battery 9.

(15) If, according to one embodiment of the method, it is provided that the EHCs 5 are only supplied in addition by means of the power P.sub.2 provided by the second battery 9 during the start phase or, in other words, no further energy transport should occur from the second battery 9 to the EHCs 5 immediately after the ending of the start phase, then it must be ensured that the first battery 8 can also provide sufficient power P.sub.1 for the two EHCs 5 after the ending of the start phase. It is shown by means of the dotted lines in FIG. 2 that, upon ending of the start phase, a state of charge SoC of the first battery of at least around 50% must be present, as long as it is assumed that the power required by the two EHCs at this time is P.sub.EHC=10 kW. In addition, or alternatively, the internal combustion engine 2 may drive an electric machine of the motor vehicle 1, not shown, in order to provide an additional power after the end of the start phase.

(16) In one embodiment of the method, the energy supply of the EHCs during the start phase is apportioned between the first battery 8 and the second battery 9 according to a firmly set provision quotient amount to a value of 2. The provision quotient is defined as the ratio of the energy E.sub.1 provided by the first battery 8 during the start phase and the overall energy E.sub.EHC required by the EHCs 5 during the start phase. Since the energy required by the EHCs amounts to E.sub.EHC=85 Wh, each of the batteries 8, 9 therefore provides 42.5 Wh. Given an overall storage capacity of the first battery 8 of E.sub.0=850 Wh, therefore 5% of the maximum cumulative energy of the first battery 8 is required. Since, during the start phase, the state of charge of the first battery 8 should not fall below the value of 25%, the first battery 8 at the beginning of the start phase must have a state of charge of 30%. Thus, the above calculated value of SoC.sub.crit=50% can basically be reduced to a value of as much as SoC.sub.crit=30%, as long as the second battery 9 and especially the DC converter 13 and the onboard network stability of the second onboard network 11 allow for providing a power of P.sub.2=5 kW for the EHCs 5 by the second battery 9 during the start phase.

(17) In one embodiment of the method, the power which can be provided by the second battery 9 is bounded at the top, namely, at P.sub.2.sup.max=2-3 kW, for example due to the stability of the second onboard network 11 not being otherwise assured, in which case a specific value of P.sub.2.sup.max=3 kW is assumed. In order to allow for this circumstance, it is advisable to apportion the power or energy supply of the EHCs 5 between the batteries 8, 9 during the start phase by a provision quotient of Q=0.3, as long as the EHCs have a constant power demand during the entire start phase. In this regard, it may be further provided that the provision quotient Q is additionally set with the help of a state of charge information describing the state of charge SoC of the batteries 8, 9, which is either ascertained by sensor and/or is present any way in the context of a controlling of the motor vehicle 1 by means of a control unit, which may be the control mechanism 12, for example.

(18) Thus, if the first battery 8 during the start phase should not fall below the state of charge SoC of 30% and if the power which can be provided by the second battery 9 is limited to P.sub.2.sup.max=3 kW, the EHCs 5 must continue to be supplied by the second battery 9 after the end of the start phase. Thus, as is also evident from the characteristic curve of FIG. 2, it is no longer possible to assure the overall power required by the EHCs of P.sub.EHC=10 kW solely by means of the first battery 8 at a state of charge of SoC=30%. The corresponding limitation of the power P.sub.2 is also particularly advantageous because in this way no further components need to be provided, which would increase the performance or onboard network stability of the second onboard network 11.

(19) Assuming that the power required by the EHCs 5 during the entire start phase is constant at P.sub.EHC=10 kW and that the second battery provides a maximum of P.sub.2=3 kW, the first battery must therefore deliver a power of P.sub.1=7 kW. From the characteristic curve 14 presented in FIG. 2 it follows that the state of charge of the first battery 8 should not fall below the value of SoC≈37%, i.e., 7% more than the above calculated value of SoC.sub.crit, corresponding to an energy quantum of around 60 Wh. Consequently, the second battery 9 must provide an energy of 25 Wh, in view of the overall energy of E.sub.EHC=85 Wh, which is the case at P.sub.2=3 Wh and a start phase duration of 30 seconds. As long as P.sub.2.sup.max takes on a value of up to 5 kW, the second battery 9 can still provide an energy during the start process of up to around 42 Wh.

(20) Speaking in general, this means that the power or energy supply of the EHCs 5 during the start phase is apportioned according to the adjustable provision quotient Q between the first battery 8 and the second battery 9. For sake of completeness, it should be mentioned in this place that the power or energy supply of the EHCs 5 can be apportioned even after the ending of the start phase according to a fixed provision quotient Q between the batteries 8, 9. It becomes clear from the concrete example just presented that the usable energy E.sub.use available on the part of the first battery 8 can be significantly increased, and in particular the so-called P/E ratio of the batteries involved, i.e., the ratio of power to energy, describing the power uptake characteristic, can be optimally utilized.

(21) German patent application no. 10 2021 103481.7, filed Feb. 15, 2021, to which this application claims priority, is hereby incorporated herein by reference, in its entirety.

(22) Aspects of the various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled.