Drive Train and Method for Operating a Drive Train

Abstract

A drive train, which is configured to electrically operate a vehicle, includes an electric motor and a first and second energy store, each of which is electrically connected to the electric motor. The drive train also includes a first inverter and a second inverter, where the first inverter is provided between the first energy store and the electric motor, and where the second inverter is provided between the second energy store and the electric motor. The electric motor has four phases.

Claims

1. A drive train configured to electrically operate a vehicle, comprising: an electric motor; a first energy store and a second energy store, each of which is electrically connected to the electric motor; and a first inverter and a second inverter, wherein the first inverter is provided between the first energy store and the electric motor, wherein the second inverter is provided between the second energy store and the electric motor, and wherein the electric motor has four phases.

2. The drive train according to claim 1, wherein at least one of the four phases is only connected to the first inverter, and another of the four phases is only connected to the second inverter.

3. The drive train according to claim 2, wherein the first inverter and the second inverter are exclusively connected on the four phases of the electric motor.

4. The drive train according to claim 3, wherein the first inverter and the second inverter are two-phase inverters.

5. The drive train according to claim 1, wherein the first energy store and the second energy store are electrically interconnected by a DC voltage converter.

6. The drive train according to claim 2, wherein the first energy store and the second energy store are electrically interconnected by a DC voltage converter.

7. The drive train according to claim 3, wherein the first energy store and the second energy store are electrically interconnected by a DC voltage converter.

8. The drive train according to claim 4, wherein the first energy store and the second energy store are electrically interconnected by a DC voltage converter.

9. The drive train according to claim 1, wherein the energy stores are batteries, accumulators, capacitors and/or fuel cells.

10. A vehicle comprising a drive train configured to electrically operate the vehicle, wherein the drive train comprises: an electric motor; a first energy store and a second energy store, each of which are electrically connected to the electric motor; and a first inverter and a second inverter, wherein the first inverter is provided between the first energy store and the electric motor, wherein the second inverter is provided between the second energy store and the electric motor, and wherein the electric motor has four phases.

11. The vehicle according to claim 10, wherein at least one of the four phases is only connected to the first inverter, and another of the four phases is only connected to the second inverter.

12. The vehicle according to claim 11, wherein the first inverter and the second inverter are exclusively connected on the four phases of the electric motor.

13. The vehicle according to claim 12, wherein the first inverter and the second inverter are two-phase inverters.

14. The vehicle according to claim 10, wherein the first energy store and the second energy store are electrically interconnected by a DC voltage converter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1: shows a schematic circuit diagram of a first form of embodiment of a drive train according to the invention.

[0025] FIG. 2: shows a schematic circuit diagram of a second form of embodiment of a drive train according to the invention.

[0026] FIG. 3: shows a schematic circuit diagram of a third form of embodiment of a drive train according to the invention.

[0027] FIG. 4: shows a schematic circuit diagram of a fourth form of embodiment of a drive train according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 shows a schematic representation of a drive train 10. The drive train 10 is, for example, a drive train for an electrically operated vehicle, such as an all-electric vehicle (BEV or FCEV), a hybrid or plug-in hybrid vehicle.

[0029] The drive train 10 comprises a first energy store 12, a second energy store 14, a first inverter 16, a second inverter 18 and an electric motor 20.

[0030] The two energy stores 12 and 14 are, for example, batteries, accumulators or capacitors. The energy stores 12, 14 can be constituted of smaller units, such as smaller batteries or accumulator cells.

[0031] However, it is also conceivable that more than two energy stores are provided in the drive train 10.

[0032] The first inverter 16 of the drive train 10 is assigned to the first energy store 12, and the second inverter 18 is assigned to the second energy store 14.

[0033] In the form of embodiment represented in FIG. 1 and FIG. 2, the first inverter 16 and the second inverter 18 are three-phase inverters, such that the inverters 16, 18 can convert direct current into an alternating current, in this case a three-phase alternating current.

[0034] The inverters 16, 18 are arranged between the energy stores 12, 14 and the electric motor 20, such that an electrical connection between one of the energy stores 12, 14 and the electric motor 24 is established by means of the respective inverter 16, 18.

[0035] The electric motor 20 has a plurality of phases 22. In the forms of embodiment represented in FIG. 1 and FIG. 2, six phases are provided.

[0036] In each case, three of the phases 22 are connected to one of the inverters 16, 18 by means of electrical lines, such that the first inverter 16 and the second inverter 18 are exclusively connected to the electric motor 20 on different phases 22.

[0037] This means that, by implication, each of the phases 22 is electrically connected either to the first inverter 16 or to the second inverter 18.

[0038] The first inverter 16 is electrically connected to the first energy store 12 by two electrical connecting lines 24, and the second inverter is electrically connected to the second energy store 14 by two further connecting lines 26.

[0039] Accordingly, a direct electrical connection is constituted between the first energy store 12 and the electric motor 20 by means of the first inverter 16, without the provision of further components between the electric motor 20 and the first inverter 16. The same applies to the second energy store 14 with respect to the second inverter 18, which connects the second energy store 14 directly to the electric motor 20.

[0040] For the operation of the drive train, i.e. for the propulsion of the vehicle or for braking, a control unit (not represented) of the drive train 10 or of the vehicle controls the drive train 10.

[0041] To this end, the following different modes of operation of the drive train 10 are available.

[0042] For moderate acceleration, energy is delivered to the electric motor 20 from the first energy store 12 or from the second energy store 14, by means of the first inverter 16 or the second inverter 18. Accordingly, the electric motor 20 assumes a maximum power, which corresponds to the maximum capacity of the first energy store 12 or of the second energy store 14.

[0043] If more power is required by the electric motor 20, or is demanded by the driver of the vehicle, additionally to the energy from the first energy store 12 (or the second energy store 14), energy is simultaneously delivered to the electric motor 20 from the second energy store 14 (or from the first energy store 12) by means of the second inverter 18 (or the first inverter 16), such that the maximum power of the electric motor now corresponds to the combined capacity of the two energy stores 12 and 14. Rapid acceleration is possible accordingly.

[0044] For braking maneuvers of the vehicle, similar modes of operation of the drive train are available. If a substantial deceleration is required, the first inverter 16, together with the first energy store 12, and simultaneously the second inverter 18 with the second energy store 14, can be regeneratively operated, such that the electric motor 20 generates electrical energy, which is simultaneously fed back to both the energy stores 12 and 14.

[0045] However, if a lesser deceleration is adequate, it is sufficient if only one of the inverters 16, 18, together with the associated energy store 12, 14 is operated regeneratively, such that electrical energy from the electric motor 20 is fed back to one of the energy stores 12 or 14.

[0046] The preference as to whether energy is to be fed back from the electric motor 20 to the first energy store 12 or to the second energy store 14 is determined by the control unit. For example, energy can consistently be fed back to the energy store 12, 14 in which less energy is momentarily stored.

[0047] In a further mode of operation of the drive train 10, energy can be transferred from one energy store 12, 14 to the other energy store 14, 12.

[0048] If, for example, energy is to be transferred from the first energy store 12 to the second energy store 14, in a braking maneuver, the second inverter 18, together with the second energy store 14, can be regeneratively operated for this purpose. At the same time, although a braking maneuver is currently in the course of execution, the first inverter 16, together with the first energy store 12, will operate in drive mode, such that energy is delivered from the first energy store 12 to the electric motor 20.

[0049] However, this energy delivered from the first energy store 12 to the electric motor 20 (in addition to the energy recovered during deceleration) is immediately fed back from the electric motor 20 to the second energy store 14 such that, effectively, a transfer of energy from the first energy store 12 to the second energy store 14 has been achieved.

[0050] In an equivalent manner, a transfer of energy can proceed between the second energy store 14 and the first energy store 12.

[0051] This type of energy transfer between the two energy stores 12, 14 is not restricted to a braking maneuver, but can also be executed during an acceleration maneuver, or during travel at a constant speed.

[0052] Thus, by means of the drive train 10, all the functions required for the operation of the drive train 10 can be executed, specifically a transfer of energy between the two energy stores 12, 14.

[0053] FIG. 2 shows a second form of embodiment of the drive train 10, which essentially corresponds to the first form of embodiment. Consequently, hereinafter, only the differences will be described, and identical or functionally equivalent components are identified by the same reference numbers.

[0054] Conversely to the drive train according to the first form of embodiment, the drive train 10 according to the second form of embodiment comprises a DC voltage converter 28. The DC voltage converter 28 is thus connected, on one side by means of the connecting lines 24 to the first energy store 12, and on the other side by means of the connecting lines 26 to the second energy store 14.

[0055] The DC voltage converter, additionally to the electrical connection via the electric motor 20, thus constitutes an additional connection between the first energy store 12 and the second energy store 14.

[0056] Via the DC voltage converter 28, energy can also be transferred from the first energy store 12 to the second energy store 14, or vice versa.

[0057] However, the DC voltage converter 28 is not employed for the transfer of the maximum energy from one of the energy stores 12, 14 to the electric motor 20, such that the selected maximum power rating of the DC voltage converter 28 can be significantly lower than the maximum capacity of one of the energy stores 12, 14. Moreover, the transfer of energy between the two energy stores 12, 14, in comparison with the energy transfer to the electric motor 20, also proceeds slowly, such that a low power rating of the DC voltage converter 28 can be selected, without influencing the function of the drive train 10.

[0058] In this manner, an efficient exchange of energy between the energy stores 12, 14 is possible, without the necessity for a large, heavy and/or expensive DC voltage converter 28.

[0059] FIG. 3 shows a schematic representation of a further form of embodiment of the drive train 10. The drive train 10 is, for example, a drive train for an electrically operated vehicle, such as an all-electric vehicle (BEV or FCEV), a hybrid or plug-in hybrid vehicle.

[0060] The drive train 10 comprises a first energy store 12, a second energy store 14, a first inverter 16, a second inverter 18 and an electric motor 20.

[0061] The two energy stores 12 and 14 are, for example, batteries, accumulators or capacitors. The energy stores 12, 14 can be constituted of smaller units, such as smaller batteries or accumulator cells.

[0062] The first inverter 16 of the drive train 10 is assigned to the first energy store 12, and the second inverter 18 is assigned to the second energy store.

[0063] In the form of embodiment represented in FIG. 3, the first inverter 16 and the second inverter 18 are two-phase inverters, such that the inverters 16, 18 can convert direct current into an alternating current, in this case a two-phase alternating current.

[0064] The inverters 16, 18 are arranged between the energy stores 12, 14 and the electric motor 20, such that an electrical connection between one of the energy stores 12, 14 and the electric motor 20 is established by means of the respective inverter 16, 18.

[0065] In the form of embodiment represented in FIG. 3, the electric motor 20 has four phases 22.

[0066] In each case, two of the phases 22 are connected to one of the inverters 16, 18 by means of electrical lines, such that the first inverter 16 and the second inverter 18 are exclusively connected to the electric motor 20 on different phases 22.

[0067] This means that, by implication, each of the phases 22 is electrically connected either to the first inverter 16 or to the second inverter 18.

[0068] The first inverter 16 is electrically connected to the first energy store 12 by two electrical connecting lines 24, and the second inverter is electrically connected to the second energy store 14 by two further connecting lines 26.

[0069] Accordingly, a direct electrical connection is constituted between the first energy store 12 and the electric motor 20 by means of the first inverter 16, without the provision of further components between the electric motor 20 and the first inverter 16. The same applies to the second energy store 14 with respect to the second inverter 18, which connects the second energy store 14 directly to the electric motor 20.

[0070] For the operation of the drive train, i.e. for the propulsion of the vehicle or for braking, a control unit (not represented) of the drive train 10 or of the vehicle controls the drive train 10.

[0071] To this end, the following different modes of operation of the drive train 10 are available.

[0072] For moderate acceleration, energy is delivered to the electric motor 20 from the first energy store 12 or from the second energy store 14, by means of the first inverter 16 or the second inverter 18. Accordingly, the electric motor 20 assumes a maximum power, which corresponds to the maximum capacity of the first energy store 12 or of the second energy store 14.

[0073] If more power is required by the electric motor 20, or is demanded by the driver of the vehicle, additionally to the energy from the first energy store 12 (or the second energy store 14), energy is simultaneously delivered to the electric motor 20 from the second energy store 14 (or from the first energy store 12) by means of the second inverter 18 (or the first inverter 16), such that the maximum power of the electric motor now corresponds to the combined capacity of the two energy stores 12 and 14. Rapid acceleration is possible accordingly.

[0074] For braking maneuvers of the vehicle, similar modes of operation of the drive train are available. If a substantial deceleration is required, the first inverter 16, together with the first energy store 12, and simultaneously the second inverter 18 with the second energy store 14, can be regeneratively operated, such that the electric motor 20 generates electrical energy, which is simultaneously fed back to both the energy stores 12 and 14.

[0075] However, if a lesser deceleration is adequate, it is sufficient if only one of the inverters 16, 18, together with the associated energy store 12, 14 is operated regeneratively, such that electrical energy from the electric motor 20 is fed back to one of the energy stores 12 or 14.

[0076] The preference as to whether energy is to be fed back from the electric motor 20 to the first energy store 12 or to the second energy store 14 is determined by the control unit. For example, energy can consistently be fed back to the energy store 12, 14 in which less energy is momentarily stored.

[0077] In a further mode of operation of the drive train 10, energy can be transferred from one energy store 12, 14 to the other energy store 14, 12.

[0078] If, for example, energy is to be transferred from the first energy store 12 to the second energy store 14, in a braking maneuver, the second inverter 18, together with the second energy store 14, can be regeneratively operated for this purpose. At the same time, although a braking maneuver is currently in the course of execution, the first inverter 16, together with the first energy store 12, will operate in drive mode, such that energy is delivered from the first energy store 12 to the electric motor 20.

[0079] However, this energy delivered from the first energy store 12 to the electric motor 20 (in addition to the energy recovered during deceleration) is immediately fed back from the electric motor 20 to the second energy store 14 such that, effectively, a transfer of energy from the first energy store 12 to the second energy store 14 has been achieved.

[0080] In an equivalent manner, a transfer of energy can proceed between the second energy store 14 and the first energy store 12.

[0081] This type of energy transfer between the two energy stores 12, 14 is not restricted to a braking maneuver, but can also be executed during an acceleration maneuver, or during travel at a constant speed.

[0082] Thus, by means of the drive train 10, all the functions required for the operation of the drive train 10 can be executed, specifically a transfer of energy between the two energy stores 12, 14.

[0083] Advantageously, the four-phase electrical machine and the two-phase inverter can be configured such that costs of the components of the drive train can be reduced. Moreover, the connecting lines between the inverters 16, 18 and the electrical machine 20 are also additionally simplified accordingly.

[0084] FIG. 4 shows a further form of embodiment of the drive train 10, which essentially corresponds to the form of embodiment represented in FIG. 3. Consequently, hereinafter, only the differences will be described, and identical or functionally equivalent components are identified by the same reference numbers.

[0085] Conversely to the drive train according to the first form of embodiment, the drive train 10 according to the second form of embodiment comprises a DC voltage converter 28. The DC voltage converter 28 is thus connected, on one side by means of the connecting lines 24 to the first energy store 12, and on the other side by means of the connecting lines 26 to the second energy store 14.

[0086] The DC voltage converter, additionally to the electrical connection via the electric motor 20, thus constitutes an additional connection between the first energy store 12 and the second energy store 14.

[0087] Via the DC voltage converter 28, energy can also be transferred from the first energy store 12 to the second energy store 14, or vice versa.

[0088] However, the DC voltage converter 28 is not employed for the transfer of the maximum energy from one of the energy stores 12, 14 to the electric motor 20, such that the selected maximum power rating of the DC voltage converter 28 can be significantly lower than the maximum capacity of one of the energy stores 12, 14. Moreover, the transfer of energy between the two energy stores 12, 14, in comparison with the energy transfer to the electric motor 20, also proceeds slowly, such that a low power rating of the DC voltage converter 28 can be selected, without influencing the function of the drive train 10.

[0089] In this manner, an efficient exchange of energy between the energy stores 12, 14 is possible, without the necessity for a large, heavy and/or expensive DC voltage converter 28.

[0090] The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.