Hybrid drive and vehicle with such a

Abstract

Hybrid drive for a vehicle (1) with a first electric machine (5) for driving a first axle (2), a second electric machine (6) for driving a second axle (3), a first power source (8) for driving the first electric machine (5), and a second power source (15) for driving the second electric machine (6), wherein the first electric machine (5) and the first power source (8) are coupled via a first line structure (9) for transmitting a first drive current, the second electric machine (6) and the second power source (15) are coupled via a second line structure (16) for transmitting a second drive current and the first and second line structures (9, 16) are coupled to one another via a connecting line structure (18) for transmitting a compensating current between the first and second power sources (8, 15), which is designed for a lower transmission power than the first and second line structures (9, 16), wherein either the first or the second current source (8; 15) is designed as an energy converter and correspondingly either the second or the first current source (15; 8) is designed as an energy store, wherein a first power electronics component (10a) is arranged between the energy converter (8) and the energy storage device (15), which first power electronics component supplies a suitable charging current to the energy storage device (15) via the connecting line structure (18), wherein the first power electronics component (10a) is arranged between the energy converter (8) and the first electric machine (5) and supplies a drive current to the latter.

Description

The present invention relates to a hybrid drive for a vehicle having a first electric machine for driving a first axle and a second electric machine for driving a second axle.In hybrid drives for vehicles, it is known to use a plurality of electric machines. There are concepts in which one electric machine is used at each of the front and rear axles. In other concepts, each drive wheel is provided with its own electric machine.In such concepts, embodiments are realized in which two electrical energy sources are available. On the one hand, an electrical energy store, which is designed, for example, as a plug-in hybrid battery or as a traction battery, and, on the other hand, an energy converter, which can be designed, for example, as an internal combustion engine generator unit or as a fuel cell arrangement.In hybrid vehicles with a purely electric drive, very powerful line structures are required for the traction network in order to transmit the required drive power via an electric line network between the energy sources and the electric machines.High-voltage on-board power supply architectures are required for this purpose, which, with corresponding power electronics, implement the required energy transmission between energy converter, energy store and an electric machine (see, for example, DE 10 2007 024 567 A1).For distributing the electrical energy between a fuel cell unit and an energy store, on the one hand, and an electric drive motor and electric auxiliary consumers, on the other hand, DE 198 10 467 C1 proposes selectively providing the electric drive motor and electric auxiliary consumers with the fuel cell or the energy store and providing a switchable connecting line between the fuel cell and the energy store.In all these approaches, a high-voltage on-board power supply system (HV on-board power supply system) or traction power supply system is required, in which the energy supply lines (power cables) must be designed such that the respective maximum powers of the energy sources are available at the main consumers (electric motors). In the case of a plurality of drives, these are usually arranged close to the axis. The energy sources are arranged between the axles in the vehicle center or likewise close to the axle in the rear or front vehicle region. The line structures required for supplying power extend through the entire vehicle in order to be able to connect all consumers in such a traction network to the available energy sources. This requires comparatively long cables with high line cross sections made of valuable and heavy conductor materials (copper) and complex measures for securing and shielding such a traction network.DE 10 2012 008 687 A1 discloses a vehicle which comprises two separate high-voltage energy supply systems each having a high-voltage energy source, a high-voltage consumer and an intermediate circuit connecting the high-voltage energy source and the high-voltage energy consumer, wherein the two high-voltage energy supply systems are coupled via a DC-DC converter.DE 11 2006 000 801 T5 and DE 10 2011 051 623 A1 describe a power supply system which is equipped with a plurality of power supply devices, each of the power supply devices being provided for driving a plurality of drive motors.It is therefore the object to provide an improved hybrid drive in which these disadvantages are at least partially eliminated. A further object can be seen in realizing a hybrid drive with an improved line network structure.According to the invention, this object is achieved by the hybrid drive according to claim 1.Further advantageous embodiments of the invention are evident from the dependent claims and the following description of preferred exemplary embodiments of the present invention.A hybrid drive according to the invention comprises a first electric machine for driving a first axle, a second electric machine for driving a second axle, a first energy source for driving the first electric machine and a second energy source for driving the second electric machine. In this case, the first electric machine and the first energy source are coupled via a first line structure for transmitting an electric drive energy, and the second electric machine and the second energy source are coupled via a second line structure for transmitting an electric drive energy.The first and second line structures are coupled to each other via a connection line structure configured for a lower line level than the first and second line structures.In such an embodiment of the line structures, the traction network (on-board power system with high voltage) can be divided into two line structures which are more or less separated from one another and independent. In the first line structure, the first energy source and the first electric machine are to be arranged compactly together in the region of the first (drive) axis. The same applies to the second electric machine and the second energy source, which are to be arranged together in the region of the second (drive) axis.There is thus a traction network region close to the first axis and a traction network region close to the second axis, which run in each case in the rear vehicle and front vehicle regions. This intelligent spatial arrangement of one energy source each (energy converter, energy store) and one energy sink each (electric machine) relative to one another makes it possible, given a corresponding division of the drive power, to reduce line losses, since the line lengths can be kept short. Thus, the electric machine (optionally with its own power electronics for converting direct current into three-phase current) and the energy source can each be combined with a (first and second) line structure, which however need only have large cross sections but only small line lengths.A connection line structure coupling the first and second line structures to each other is designed for a lower power level than the first and second line structures. This is possible since it does not serve for the transmission of the drive power, but rather only needs to transmit a compensation power (e.g. a charging current, supply of loads in a low-voltage on-board power supply).This allows the use of lines to which lower requirements have to be placed with regard to the line cross section, the material and optionally also the shielding and insulation. In such a topology, a connection of the first and second line structures is possible in a weight-saving and cost-saving manner despite the required line length.In this case, there are embodiments in which one of the two current sources is designed as an energy converter, in particular a fuel cell arrangement, and the respective other current source is designed as an energy store, in particular as a battery arrangement. Different hybrid drive alternatives can thus be realized.In an operating state, the drive energy is provided exclusively via the first power source, the energy converter, the first electric machine, which is coupled to the first drive axle. The energy converter can be designed as a fuel cell arrangement or as an internal combustion engine generator unit. An available energy surplus exceeding the necessary drive energy can be used in this operating state via the connecting line structure for charging the second current source (e.g. a battery arrangement serving as an energy store). The charging energy to be transferred in this case is significantly lower than the required driving energy and can therefore be easily transferred via the connecting line structure which is designed for a lower power level.In another operating state, the drive takes place exclusively via the second energy source, the energy store, which drives the second electric machine on the second drive axle via the corresponding line structure. Operation of the energy converter is not necessary in this operating state. Operation would thus be completely exhaust-free.It is also possible to operate the energy converter in parallel with the drive of the second drive axle via the energy store in order to supply the energy store with a charging current which slows down its emptying during the driving operation (a type of range extender operation). Here too, the charging current is supplied from the energy converter via the connecting line structure. The energy transferred in this case is below the drive energy supplied by the energy store to the electric machine.Finally, both energy sources can also be used for simultaneously driving both axles. Depending on the performance of the energy converter, the latter can also provide charge energy via the connecting line structure in parallel with the drive energy.For the driving / operating states described above, the connecting line structure is configured to transmit a charging current between the first power line structure and the second power line structure to the energy store.According to the invention, a power electronics component is arranged between the energy converter and the energy store, which supplies a suitable charging current via the connecting line structure to the energy store. A corresponding power electronic component ensures that a suitable charging current is supplied from the energy converter to the energy store. An operating and / or charge state dependent control controls the strength and voltage of the desired charging current.According to the invention, the power electronic component is additionally suitable for supplying a corresponding drive current to the first electric machine. Particularly suitable for this purpose are DC-DC converters which, given a corresponding embodiment and suitable actuation, can provide both the drive energy and the charging energy.In another embodiment, the first and / or the second electric machine can be operated in generator operation. Thus, a suitable charging current can be supplied from the first and / or the second power line structure to the energy store via the first and / or a second power electronic component.In such an embodiment, further operating states of the hybrid drive are possible: a recuperation mode in which, via one or both drive axles in generator mode, the electric machines generate charging energy, which is supplied to the energy store. A road-coupled generator mode in which the one electric machine, which is coupled to the energy converter, drives the vehicle via one axle, while the electric machine travels along the other axle in the generator mode and in the process absorbs a portion of the drive energy, converts it into charging energy and supplies it to the energy store.There are also embodiments in which the first and second line structures each form a separate traction network and these are coupled to one another via an on-board power supply system (low-voltage on-board power supply system), wherein the on-board power supply system is coupled to the respective first and second line structures via a potential-isolated DC-DC converter. The required connecting line structure for connecting the first and second line structures can thus simultaneously also serve as a component of the on-board power supply system for further consumers (on-board power supply system battery, standard consumers such as lamps, servomotors, pumps, etc.).The invention further relates to a vehicle provided with the hybrid drive described in more detail above.Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings. The following shows: FIG. 1 shows a schematic illustration of a first exemplary embodiment of a hybrid drive according to the invention, and FIG. 2 shows a schematic illustration of a second exemplary embodiment of a hybrid drive according to the invention.A first exemplary embodiment of a hybrid drive according to the invention is illustrated in FIG. 1.A vehicle 1 is schematically shown with a first axle designed as a front axle 2 and a second axle designed as a rear axle 3, which are each provided with two drive wheels 4. Electric machines are arranged on the two drive axles 2, 3. A first electric machine designed as a front wheel drive 5 and a second electric machine designed as a rear wheel drive 6, which each act via a transmission 7 on the axle 2, 3 or the drive wheels 4. The front wheel drive 5 is supplied with electrical energy via an energy converter 8, which is designed here as a fuel cell arrangement and forms a first current source. A first line structure 9 is used for this purpose, which is a component of a traction network.In another embodiment, not shown, the energy converter 8 can also be designed as an internal combustion engine generator unit, which supplies the front wheel drive 5 with electrical drive energy via the first line structure 9.Acting between the energy converter 8 and the front wheel drive 5 is a power electronic component designed as a DC-DC converter 10 a, which adjusts the electrical energy of the energy converter 8 (operating voltage: for example 250-370 volts) to the voltage / power level of the front wheel drive (operating voltage: for example 300 volts).Optionally, the first line structure 9 comprises a terminal box 11 (power distribution device), via which energy converter 8, DC-DC converter 10 aand front wheel drive 5 are electrically coupled to one another.The line structure 9 is a traction network component which has corresponding line cross sections, insulations and safety devices. In order to shorten line lengths and thus to save weight and material, the units energy converter 8, front wheel drive 5 and DC-DC converter 10 aare spatially combined here in a front end region close to the front axle 2. The energy converter 8 is supplied with fuel (for example with hydrogen, gasoline or diesel fuel) from a storage tank 14 via a fuel line 13.The rear wheel drive 6 is supplied with drive energy via a second line structure 16 via an energy store 15, which is designed as a battery arrangement and serves as a second current source. Here too, the energy distribution is optionally effected via a second DC-DC converter 10 band an optional terminal box 17 which serves as a current distribution device.Energy storage device 15, rear wheel drive 6 and, if appropriate, the terminal box 17 are spatially combined close to the rear axle 3 in order to realize short line lengths in the second line structure 16 which forms the second traction network in a cost-saving, material-saving and weight-saving manner. Optionally, the front wheel drive 5 and the rear wheel drive 6 comprise an additional power electronic component 12 which converts the supplied electrical direct current into a suitable three-phase current, if appropriate.The energy store 15 is designed as a traction battery and provides a voltage of 300 volts, for example, and supplies this current to the rear wheel drive 6, which operates as a synchronous machine with a voltage of 300 volts, for example, like the front wheel drive 5, and optionally also has a power electronic component 12 which converts the direct current provided into a corresponding three-phase current.The first line structure 9 and the second line structure 16 are connected to one another via a connecting line structure 18 which extends between the front axle region and the rear axle region. This line structure is designed for a lower transmission power than the first and second line structures 9 and 16. The connecting line structure 18 serves in particular to deliver a charge current from the energy converter 8 or from the first line structure 9 to the energy store 15 or to the second line structure 16. The connecting line structure 18 is designed for a lower voltage range (for example with a typical vehicle electrical system voltage of 12 volts) and a lower transmission power. The corresponding lines of the connecting line structure 18 can therefore be designed with correspondingly smaller cross sections, simple line layout (flying line) and largely without separate safety measures.Corresponding power electronics, either in the form of the DC-DC converter 10 a present or in the form of a separate component, supply the desired power (voltage, current intensity) to the connecting line structure 18, which is connected either via the terminal box 17 or directly to the energy store 15. A second DC-DC converter 10 bis optionally provided in order to ensure a power supply according to requirements between energy store 15 and rear wheel drive 6 and between connecting line structure 18 and energy store 15.With this grid topology, in which a device-specific power distribution is realized via the connecting line structure 18 in the case of a plurality of energy sources (energy converters 8, energy stores 15) and a plurality of drives (front wheel drive 5, rear wheel drive 6), a plurality of effects are achieved: 1. the traction grids (first line structure 9 and second line structure 16) are largely independent of one another and can be realized with very short line paths in the front end region or in the rear end region. 2. the front wheel drive 5 and the rear wheel drive 6 can be operated separately and independently of one another (pure front wheel drive, pure rear wheel drive, all-wheel drive with any desired power distribution between front and rear axles). 3. the energy store 15 can also be charged during the driving operation:either in a front wheel drive state in which excess electric energy not required for the drive is supplied to the energy store 15 via the connecting line structure 18,in coasting operation, in which both or one of the front wheel drives 6 or the rear wheel drives 5 respectively operate in generator operation and convert the power absorbed during braking into electrical energy and supply this to the energy store 15 (recuperation), orin a combined propulsion / coasting mode, in which the front wheel drive 5 is driven via the energy converter 8, and the rear wheel drive 6 rotates in the drag mode and supplies electrical energy to the energy store 15 in the generator mode.FIG. 2 shows a second exemplary embodiment of a hybrid drive according to the invention, in which the connecting line structure 18 is separated from the first line structure 9 and the second line structure 16 via two potential-separated DC-DC converters 181, and is part of an on-board power supply system 180, which is provided with its own energy store, which is designed as an on-board power supply battery 182 and via which further loads such as headlights 183, units, actuating drives, etc. are supplied.In this topology, both the on-board power supply system 180 with its on-board power supply system battery 182 and the energy store 15 can be supplied via the connecting line structure 18, either from the energy converter 8 (even when the vehicle is stationary) or regeneratively / generatingally via the front wheel drive 5 from the first line structure 9 and / or via the rear wheel drive 6 from the second line structure 16 in coasting or (partial) towing operation. The on-board power supply system 180 can likewise be supplied from the second line structure 16 via the energy store 15.List of reference characters1 Vehicle 2 Front axle 3 Rear axle 4 Drive wheels 5 Front wheel drive (first electric machine) 6 Rear wheel drive (second electric machine) 7 Transmission 8 Energy converter (first current source) 9 First line structure 10 aFirst DC voltage converter 10 bSecond DC voltage converter 11 Terminal box 12 Power electronics component (optional) 13 Fuel line 14 Storage tank 15 Energy store (second current source) 16 Second line structure 17 Terminal box 18 Connecting line structure 180 On-board network 181 Potential-isolated DC voltage converter 182 On-board network battery 183 Headlights

Claims

Hybrid drive for a vehicle (1) having a first electric machine (5) for driving a first axle (2), a second electric machine (6) for driving a second axle (3), a first current source (8) for driving the first electric machine (5), and a second current source (15) for driving the second electric machine (6), wherein the first electric machine (5) and the first current source (8) are coupled via a first line structure (9) for transmitting a first drive current, the second electric machine (6) and the second current source (15) are coupled via a second line structure (16) for transmitting a second drive current, and the first and second line structures (9, 16) are coupled to one another via a connecting line structure (18) for transmitting a compensation current between the first and second current sources (8, 15), which is designed for a lower transmission power than the first and second line structures (9, 16), wherein either the first or the second current source (8; 15) is designed as an energy converter and correspondingly either the second or the first current source (15; 8) is designed as an energy store, wherein a first power electronics component (10a) is arranged between the energy converter (8) and the energy store (15), which supplies a suitable charging current via the connecting line structure (18) to the energy store (15), wherein the first power electronics component (10a) is arranged between the energy converter (8) and the first electric machine (5) and supplies a drive current thereto.Hybrid drive according to Claim 1, wherein the energy converter (8) is a fuel cell arrangement.Hybrid drive according to Claim 1 or 2, wherein the energy store (15) is a battery arrangement.Hybrid drive according to one of the preceding claims, wherein the connecting line structure (18) is designed to transmit a charging current to the energy store (15) between the first line structure (9) and the second line structure (16).Hybrid drive according to one of the preceding claims, wherein the first power electronic component (10a) is designed as a DC-DC converter.Hybrid drive according to one of the preceding claims, wherein the first and / or second electric machine (5; 6) can be operated in the generator mode and, in this operating state, supplies a suitable charging current via the first (10a) and / or a second power electronic component (10b) to the energy store (15).Hybrid drive according to one of the preceding claims, in which the first and the second line structure (9, 16) each form a traction network, wherein each is coupled via a potential-isolated DC-DC converter (181) to an on-board network (180) which comprises the connecting line structure (18).Vehicle (1) with a hybrid drive according to one of the preceding claims.

Images