Track-type construction machine

Abstract

A track-mounted railway construction machine (1, 40) is described, comprising a machine frame (23) movable on rail bogies (8) with electric travel drives (27), a current collector system (38, 37, 42, 36, 35) for collecting power from an overhead line network (39), and optionally a direct current intermediate circuit (48). In order to create advantageous design and operating conditions, it is proposed that an electric machine (30) be provided which can be operated both as an electric motor and as an electric generator, which on the one hand is drive-connected to an internal combustion engine (10) via a first clutch (K1) and on the other hand is drive-connected to at least one hydraulic pump (20) for operating hydraulically driven work units (2, 4, 41) via a second clutch (K2).

Description

[0001] The invention relates to a track-mounted railway construction machine, comprising a machine frame movable on rail bogies with electric travel drives, optionally a driver's cab, a current collector system for collecting current from an overhead line network and optionally a direct current intermediate circuit and at least one hydraulic pump for operating hydraulically driven working units.

[0002] Such a track-mounted railway construction machine is disclosed, for example, in EP4230463A1. Railway construction machines are built and used for the construction, reconstruction, and maintenance of tracks, subgrades, and overhead lines. The track machines are predominantly built with a diesel-hydraulic or diesel-mechanical drive concept. A diesel engine drives a hydrodynamic transmission with multiple outputs. On the one hand, the axle drives are driven directly from the transmission via cardan shafts; on the other hand, hydraulic pumps are connected to the transmission outputs, operating a hydraulic circuit. This hydraulic circuit also provides hydrostatic axle drives for driving the machine and supplying the work units.Working units can be tamping units, lifting and straightening units, drive motors for cleaning chains, hydraulic cylinders for positioning the conveyor chains, drives for conveyor belts or lifting platforms, tensioning drums for unwinding or winding contact wires, ploughs and others.

[0003] In the fight against climate change, the international community, and in particular the European Union, is making significant efforts to limit CO2 emissions. A sustainable solution for environmentally friendly and low-carbon energy supply for new buildings is therefore highly desirable.

[0004] The following state-of-the-art options are available for this purpose. If a country has a high proportion of electrified lines, the energy for operating the machines can be supplied via the overhead line. This requires the installation of a pantograph, a high-voltage transformer, with subsequent rectification of the alternating voltage using, for example, a 4-quadrant converter. The generated direct voltage can then be converted to three-phase voltage via traction inverters to operate the electric motors. Inverters can also be used to generate auxiliary voltages for operating other devices such as computers, air compressors, air conditioning systems, lighting, valves, control systems, etc.

[0005] For non-electrified lines or construction sites where the overhead line must be switched off, the power supply for the railway construction machines is not sufficient. Additional electrical batteries and supercapacitors could provide short-term energy for these phases. Their use is generally advantageous because they compensate for voltage peaks during strong power fluctuations, such as in tamping machines that cyclically move from sleeper to sleeper. However, shifts for track construction machines usually last eight hours. Often, on larger construction sites, several shifts are operated continuously one after the other. Batteries can therefore only provide energy for railway construction machines for a short time at best, and can therefore only be used to temporarily bridge a power outage.On non-electrified routes, diesel engines with downstream electric generators, i.e. diesel-electric drives, can therefore be used to supplement the power supply via overhead lines.

[0006] A railway construction machine with a diesel-electric drive concept is known from AT517558, in which an internal combustion engine with a drive shaft is mechanically connected to both electric generators and hydraulic pumps via a transmission. This enables the electrical supply of the drives. Diesel engine operation results in a small saving in fossil energy, which results primarily from the higher efficiency of electric drives.

[0007] WO2017 / 050414 discloses a similar machine with a diesel engine that can be coupled via a clutch to a transfer case, to which hydraulic pumps for supplying a hydraulic system, an electric motor, and a generator are connected. When power is supplied from the overhead line, the diesel engine is uncoupled from the transfer case, and the electric motor and electric generator are coupled to the transfer case. The disadvantage of this solution is that both an electric motor and an electric generator are required. In addition to the cost, other disadvantages include the large amount of space required and the additional weight.

[0008] A lightweight and compact hybrid traction drive for rail vehicles is known from DE 10 2018 124 887 A1. This traction drive makes it possible to replace a manual transmission and a starting clutch with two clutches that are not used for starting, allowing them to be designed much simpler and more compactly. This eliminates the need for a manual transmission and a starting clutch, which were previously considered necessary for internal combustion engines.

[0009] The invention is based on the object of creating a particularly compact device of the type described above, which requires only a few components and which offers the possibilities of a purely fuel-electric drive, an overhead line-supported drive or a combination of fuel-electric energy and overhead line-supported drive both for pure driving operation and for the working operation of the working units.

[0010] The invention achieves this objective by providing an electric machine that can be operated both as an electric motor and as an electric generator, which is drive-connected to an internal combustion engine via a first clutch and is drive-connected to the at least one hydraulic pump for operating the hydraulically driven working units via a second clutch. The electric machine, which can be operated both as an electric motor and as an electric generator, has a continuous shaft, to the first end of which the first clutch is connected and to the second end of which the second clutch is connected. The electric machine is therefore an electric motor / generator with an armature shaft that is equipped with a clutch at both ends, i.e., at opposite ends.

[0011] The electric machine has a continuous mechanical shaft with mechanical couplings on both sides. One of the couplings is connected to the diesel engine, preferably without an intermediate gear, while the other is connected to a mechanical transfer case or directly to the hydraulic pump(s). Several hydraulic pumps can be flanged to the transfer case, which supply power to the construction machine's working units. Depending on the position of the couplings (engaged or disengaged), a wide variety of operating modes can be selected.

[0012] This creates a hybrid drive system consisting of an internal combustion engine, particularly a diesel engine, a pantograph system, and an electric machine that can operate both as an electric motor and as an electric generator. The pantograph system draws power from the overhead line. A DC link can be supplied via a transformer and converter from the overhead line and / or from the electric machine driven by the internal combustion engine. An energy storage device in the form of accumulators and / or supercapacitors can be connected to the DC link.

[0013] The electric traction drives are preferably connected to the DC link via traction converters. Appropriate drive controllers can be provided to control the traction converters.

[0014] The separation of pure driving mode, for example, for transferring the construction machine to the job site, from work mode, which includes driving mode and the operation of work units, is essential for increasing efficiency of this construction machine. The drive train for pure driving mode does not include a transfer case, thus being transfer case-free. This avoids power losses that occur in the transfer case.

[0015] The various operating modes that can be realized with the track-mounted construction machine are shown as examples in the description of the figures.

[0016] The drawing shows an example of the subject matter of the invention. Fig. 1 and 2 known (SdT) track-mounted construction machines in schematic side view, Fig. 3 a circuit diagram of a construction machine according to the invention, Fig. 4a first part of a construction machine according to the invention in a schematic side view and Fig. 5 a second part of the construction machine according to the invention Fig. 4 in schematic side view.

[0017] Fig. 1 shows, as an example of known railway construction machines, a track-mounted tamping machine 1, comprising a machine frame 23 movable on rail bogies 8 with electric travel drives and two driver's cabs 51 as well as a work cabin 21. The working direction is indicated by C. A hydrodynamic transmission 9 with a pump 20 is driven by an internal combustion engine 10, in particular a diesel engine. The pump 20 generates a hydraulic circuit to which various actuators such as the lifting / lowering cylinder 18 of the tamping unit, fully hydraulic tamping drives of the

[0018] Tamping unit 4, lifting cylinder 5 of a lifting and straightening unit 2 and a longitudinal displacement cylinder of unit 19 are connected. The machine is equipped with bogies and railway wheelsets 25. To increase the drive power, one of the axles is equipped with a hydrostatic traction motor 16 which acts on the axle gear 15. The hydrodynamic gearbox drives the axle gears 13 of two wheelsets via cardan shafts 26 which are mechanically connected directly to the gearbox. The on-board DC voltage of 24VDC is generated via an alternator 12 which is flanged to the diesel engine 10. A battery 11 is connected in parallel to the alternator. 380 / 220VAC is generated via a DC / AC converter 17, which supplies various devices such as computers, screens or air conditioning systems. The drive systems, brakes and working electronics are controlled and regulated via a control computer 46.The drive principle is often the same for ballast levelers, overhead line vehicles, track measuring vehicles, grinding machines, dynamic track stabilizers, and material conveyor silo units.

[0019] Fig. 2another well-known version of railway construction machines 1, 8. Some railway authorities and customers require axle loads that are significantly lower than the 22.5 tonnes generally permitted in Europe. This is often difficult to achieve with single-part railway construction machines. Therefore, the power supply for the combustion engine 10, distribution gearbox 24, hydraulic pumps P, hydraulic tank and diesel tank is shifted from the main machine 1 to a trailer 40 to reduce the weight. This trailer is often used to install additional work units such as a dynamic track stabilizer, a sweeper with steep conveyor belt and silo, a plow device or an intermediate compartment compactor. The on-board power supply of 24 VDC is also generated on the trailer 40 via an alternator 12 with a battery 11 connected in parallel. 380 / 220 VAC is generated via DC / AC converters 17 and supplies the devices with mains voltage.Valves, indicators, limit switches, and other loads are connected to the 24VDC rail and thus supplied with power.

[0020] The control computer 46 controls and regulates the travel drives, brakes, and work electronics. The travel drive of these machines is often hydrostatic. Some axles are equipped with axle drives 13, 15, which are driven by hydraulic motors 16. As can be seen from the diagram, for example (but frequently encountered in practice), the two front axles in the working direction C are driven on the machine 1 shown. This means that long hydraulic supply lines must be routed from the distribution gear 24 via the driven pumps P to the front over the vehicles 1, 8. This has the disadvantage that the response time of the drives is slowed by the propagation pulse and the stretching of the hoses. This is particularly disadvantageous when working from threshold to threshold, when a fast response of the machine is decisive for work performance.Another disadvantage of hydraulic drives is the oil leakage in the event of a failure. The travel drives 16 typically operate at pressures of up to 350 bar, which means a large loss of hydraulic oil in the event of a failure.

[0021] Fig. 3shows a circuit diagram of a track-mounted construction machine 1, 40 according to the invention, namely a trailer 40 coupled to the main machine 1, on which the energy supply for the construction of a modular hybrid drive is located. The energy for various electric drives 27 is provided via a DC intermediate circuit 48. The intermediate circuit voltages common in the railway industry are typically 750 VDC. According to the invention, current is taken from an overhead line network (39) via a current collector system (38, 37, 42, 36, 35). The current collector system (38, 37, 42, 36, 35) comprises a current collector 38. The voltage is fed to a high-voltage transformer 36 via a main switch 37. On the secondary side, for example, a 4-quadrant controller 35 is set up which supplies the DC intermediate circuit 48. Connected to this are an energy storage device (e.g. lithium-ion polymer battery) 34 and / or a supercapacitor unit 33.The energy storage 34 and the.

[0022] Supercapacitor units 33 can provide short-term power. They also serve to buffer rapidly changing load requirements, such as those encountered in tamping machines due to the constant starting, braking, and tamping from sleeper to sleeper.

[0023] The internal combustion engine 10 is connected, on the one hand, to the electric machine 30 via a mechanical / electrical clutch K1. The electric machine 30 has a through shaft (indicated by dashed lines) and, on the other hand, is connected to a mechanical clutch K2. A mechanical transmission, possibly a transfer case 29, is connected to the clutch K2, which drives hydraulic pumps 20 at the outputs. These hydraulic pumps supply working units such as tamping units 4, lifting-straightening units 2, or other hydraulic devices 41 via hydraulic lines 47.

[0024] By means of a switch S1, the electric machine 30 can either supply the DC intermediate circuit 48 with energy via an inverter 43, or be supplied with energy from the DC intermediate circuit 48 via a rectifier 44 and operated as a motor. Switch S1 can also be used to disconnect the electric machine 30 from the DC intermediate circuit 48.

[0025] The following important operating modes arise: overhead line diesel engine Generator / Engine Clutch K1 Clutch K2 Operating mode 0 0 0 0 0 1. Standstill 1 0 0 0 0 2. DRIVE via overhead line 0 1 1 1 1 3. WORKING MODE DIESEL ENGINE: Electric generator supplies DC link (working driving) and through drive supplies hydraulic pumps (working unit supply) 1 1 1 1 0 4. COMBI-RIDE: DC link supplied via electric generator and overhead line (steep section ride) 1 1 0 1 1 5. COMBINED WORK OPERATION: Drive power of diesel engine and electric motor overlap (steep slope work) 0 1 1 1 0 6. DRIVE via diesel engine 1 0 0 0 1 7. OVERHEAD LINE OPERATION: Electric motor drives gearbox (working unit supply) and DC link for working travel Overhead line: 0 powerless 1 live Diesel engine: 0 not in operation 1 in operation Generator / Engine: 0 Motor 1 generator Clutch K1: diesel engine) 0 disengaged (no energy supply via 1 engaged (power supply via diesel engine) Clutch K2: 0 disengaged (working operation not possible) 1 engaged (working mode)

[0026] The electric traction drives 27 are connected to the DC link 48 via traction converters 28.

[0027] If the construction machine can be supplied with power via an overhead line 39 and the pantograph system 38, 37, 42, 36, 35 is connected to the overhead line, then the DC link 48 is supplied with power from the overhead line. The internal combustion engine 10 and the electric motor 30 are switched off, and the clutches K1, K2 are disengaged. Switch S1 is in the zero position. For short periods of time, e.g., on inclines, energy can also be provided via power storage units 33, 34 connected to the DC link 48. This results in purely electric operation via the overhead line.

[0028] If no overhead line 39 is present, then in purely fuel-electric driving mode, the internal combustion engine 10 runs, the clutch K1 is engaged, and the electric motor 30 is in generator mode. The DC link 48 is supplied with energy via the electric motor 30, the switch S1, and the inverter 43. This can be used to supply the electric traction drives 27. Pure diesel-electric driving is present. The clutch K2 is disengaged.

[0029] For purely electric operation, the overhead line network 39 is connected to the DC link 48 via the pantograph system 38, 37, 42, 36, 35, with the clutch K1 being disengaged when the internal combustion engine 10 is switched off, the electric machine 30 operating in motor mode being connected to the DC link 48 via an inverter 44, and the electric machine 30 driving at least one hydraulic pump 20 for operating hydraulically driven work units 2, 4, 41 when the clutch K2 is engaged. The operation is powered purely electrically via the overhead line 39 (and / or with the aid of a power storage device).

[0030] For operation solely with the drive power of the internal combustion engine 10, the clutch K1 is engaged, and the electric machine 30, which operates in generator mode to generate electricity, is connected to the DC link 48 via the switch S1 and an inverter 43. When the clutch K2 is engaged, the internal combustion engine 10 also drives at least one hydraulic pump 20 for operating hydraulically driven working units.

[0031] In the embodiment according to the invention, the construction machine 1, 40 also offers the possibility of pulling work wagons as a towing vehicle, even on steeper gradients. Loading wagons typically carry equipment and materials, as well as ballast wagons or crew vehicles, etc., which are required for track construction work at the construction site.

[0032] Steep gradients require more power. For this purpose, the traction force can be increased by combining the power supply from the overhead line 39 and the internal combustion engine 10 via the electric motor 30 operating in generator mode.

[0033] For this purpose, power can be supplied to the DC intermediate circuit 48 for combined driving operation on track 3 on the one hand from the current collector system 38, 37, 42, 36, 35 and on the other hand from the internal combustion engine 10, wherein the switching clutch K1 is engaged and the electric machine 30 operating in generator mode to generate electricity is connected to the DC intermediate circuit 48 via an inverter 43 and the switching clutch K2 is disengaged.

[0034] In this combined supply mode, the DC link is supplied on the one hand via the overhead line system - pantograph 38, circuit breaker 37, transformer 36 and 4-quadrant controller 35 - and additionally via the internal combustion engine, clutch K1 engaged and clutch K2 disengaged, electric generator 30, switch S1 and inverter 43.

[0035] However, even during working operation on steep uphill stretches, more power may be required. For combined working operation on track 3, the power supply to the DC link 48 can be provided, on the one hand, by the pantograph system 38, 37, 42, 36, 35 and, on the other hand, by the internal combustion engine 10. With the clutch K1 engaged, the electric machine 30 operating in motor mode is connected to the DC link 48 via an inverter, and with the clutch K2 engaged, the internal combustion engine 19 and the electric machine 30 jointly drive at least one hydraulic pump 20 for operating hydraulically driven working units 2, 4, 41. In this case, too, the power of the internal combustion engine 10 can be supplemented with energy from the overhead line 39.

[0036] Various auxiliary voltages VDCi (such as the on-board voltage of 24VDC) can be generated via dedicated AC / DC converters 45. Typical consumers 52 such as air conditioning systems and computers can be connected and operated via the 380 / 220VAC three-phase network. The machine control systems 32 and 46 communicate via dedicated control lines. These also communicate with the driver's cabs, and the drives are coordinated.

[0037] The system boundary 50 between trailer 40 and main engine 1 is in Fig. 3 represented by a dashed line.

[0038] Fig. 4schematically shows the trailer 40 which carries the power supply and is coupled to the main machine 1 (working machine). The trailer 40 comprises a driver's cab 51 with an outer door 22, a machine control system 32 and runs on rail bogies 8. The rail bogies 8 are driven by electric travel drives 27 and axle drives 13. The trailer 40 rests on the vehicle frame 23 on the rail bogies 8 which run on the railway tracks 3. The DC intermediate circuit 48 is supplied via the pantograph 38, the circuit breaker 37, the high-voltage transformer 36 and the 4-quadrant controller 35. The voltage of the DC rail 48 is also buffered via energy storage devices 34 and / or supercapacitors 33. The travel drives 27 are supplied and controlled via traction inverters 28. In addition to the internal combustion engine 10, the vehicle 40 carries an electric machine 30 that can be operated both as an electric motor and as an electric generator.The electric machine 30 has a through shaft. Clutches K1 and K2 are located on both sides of the shaft. These connect the electric machine 30 to the internal combustion engine 10 on the one hand, and to the transfer case 29 on the other. Hydraulic pumps 20 are flanged to the transfer case. These pumps supply the machine's working units via hydraulic lines 47 during operation. An inverter 31 generates 380 / 220 VAC to power various devices such as heaters, fans, or air conditioning systems. The DC busbar 48, the hydraulic lines 47, and the AC busbar 49 are routed from the trailer 40 to the main machine 1.

[0039] Fig. 5shows a schematic of the coupling of trailer 40 to main machine 1. The DC link 48, the AC rail 49, and the hydraulic lines 47 lead from trailer 40 to main machine 1. The frame 23 of the machine rests on rail bogies 8. The front rail bogie 8 is driven by electric travel drives 27. The electric travel drives 27 drive the axles via axle drives 13. A tamping machine is shown as an example of a track machine 1. This has tamping units 4 and a lifting and straightening unit 2. These units are hydraulically driven via the hydraulic supply 47. The tamping unit 4 has fully hydraulic tamping drives and a lifting-lowering cylinder 18. The lifting-straightening unit 2 has a lifting cylinder 5 or a longitudinal displacement cylinder 19. In addition, the lifting-straightening unit 2 has a roller clamp 6, a lifting hook 7, and a straightening roller 14.Machine 1 has an electronic control system 46 that regulates and controls the work processes as well as the coordination with the trailer 40. Various required DC voltages VDCi are generated via a converter 45. The traction converters 28 control the travel drives 27. Machine 1 has a driver's cab 51.

[0040] The machine has a tamping cabin 21. The machine works in working direction C.

[0041] Of course, the entire supply section (fuel and overhead line supply) can also be installed on a single-piece construction machine if weight and space requirements allow it.

Claims

1. A track-mobile railway construction machine (1, 40), comprising a machine frame (23) movable on rail bogies (8) with electric travel drives (27), optionally a driver's cab (51), a current collector system (38, 37, 42, 36, 35) for collecting power from an overhead line network (39) and optionally a DC intermediate circuit (48) and at least one hydraulic pump (20) for operating hydraulically driven working units (2, 4, 41), characterized in that an electric machine (30) which can be operated both as an electric motor and as an electric generator is provided, which on the one hand is drive-connected to an internal combustion engine (10) via a first clutch (K1) and on the other hand is drive-connected to the at least one hydraulic pump (20) for operating the hydraulically driven working units (2, 4, 41) via a second clutch (K2).

2. Track-mounted construction machine (1, 40) according to claim 1, characterized in thatthe electrical machine (30) which can be operated both as an electric motor and as an electric generator has a continuous shaft, to the first end of which the first clutch (K1) is connected and to the second end of which the second clutch (K2) is connected.

3. Track-mounted construction machine (1, 40) according to claim 1 or 2, characterized in that the electric drive units (27) are connected to the DC link (48) by means of a traction converter (28).

4. Track-mounted construction machine (1, 40) according to one of claims 1 to 3, characterized in that the current collector system (38, 37, 42, 36, 35) which can be connected to an overhead line network (39) is connected to the direct current intermediate circuit (48) for purely electric operation on the track (3), wherein the internal combustion engine (10) and the electric machine (30) are switched off and the switching clutches (K1, K2) are preferably disengaged.

5. Track-mounted construction machine (1, 40) according to one of claims 1 to 3, characterized in that for pure driving operation on the track (3) purely with the drive power of the internal combustion engine (10), the switching clutch (K1) is engaged, the switching clutch (K2) is disengaged, the electric machine (30) operating in generator mode to generate electricity is connected to the DC intermediate circuit (48) via an inverter (43).

6. Track-mounted construction machine (1, 40) according to one of claims 1 to 3, characterized in thatfor purely electric operation, the current collector system (38, 37, 42, 36, 35) which can be connected to an overhead line network (39) is connected to the DC intermediate circuit (48), wherein the switching clutch (K1) is disengaged when the internal combustion engine (10) is switched off, wherein the electric machine (30) operating in motor mode is connected to the DC intermediate circuit (48) via an inverter and wherein the electric machine (30) drives the at least one hydraulic pump (20) for operating hydraulically driven working units (2, 4, 41) when the switching clutch (K2) is engaged.

7. Track-mounted construction machine (1, 40) according to one of claims 1 to 3, characterized in thatfor working operation purely with the drive power of the internal combustion engine (10), the clutch (K1) is engaged, the electric machine (30) operating in generator mode to generate electricity is connected to the DC intermediate circuit (48) via an inverter (43), and that the internal combustion engine (10), when the clutch (K2) is engaged, drives at least one hydraulic pump (20) for operating hydraulically driven working units (2, 4, 41).

8. Track-mounted construction machine (1, 40) according to one of claims 1 to 3, characterized in thatthe power supply to the DC intermediate circuit (48) for combined driving on the track (3) is effected on the one hand by the current collector system (38, 37, 42, 36, 35) and on the other hand by the internal combustion engine (10), wherein the switching clutch (K1) is engaged and the electric machine (30) operating in generator mode to generate power is connected to the DC intermediate circuit (48) via an inverter (43) and the switching clutch (K2) is disengaged.

9. Track-mounted construction machine (1, 40) according to one of claims 1 to 3, characterized in thatthe power supply to the DC intermediate circuit (48) for combined working operation on the track (3) is effected on the one hand by the current collector system (38, 37, 42, 36, 35) and on the other hand by the internal combustion engine (10), wherein the switching clutch (K1) is engaged, the electric machine (30) operating in motor mode is connected to the DC intermediate circuit (48) via an inverter and wherein the internal combustion engine (19) and the electric machine (30) jointly drive the at least one hydraulic pump (20) for operating hydraulically driven working units (2, 4, 41) when the switching clutch (K2) is engaged.

10. Track-mounted construction machine (1, 40) according to one of claims 1 to 3, characterized in thatat least one power storage device (33, 34) is connected to the direct current intermediate circuit (48) and that for driving on the track (3) purely with the drive power of the power storage device (33, 34) the internal combustion engine (10) and the electric machine (30) are switched off and the switching clutches (K1, K2) are preferably disengaged.

11. Track-mounted construction machine (1, 40) according to one of claims 1 to 3, characterized in thatfor a working operation purely with the drive power of a power storage device (33, 34) connected to the direct current intermediate circuit (48), the internal combustion engine (10) is switched off, the switching clutch (K1) is disengaged, the electric machine (30) operating in generator mode to generate power is connected to the direct current intermediate circuit (48) via an inverter (43), the switching clutch (K2) is engaged and the electric machine (30) drives at least one hydraulic pump (20) for operating hydraulically driven working units (2, 4, 41).

12. Track-mounted construction machine (1, 40) according to one of claims 1 to 3, characterized in that for charging a power storage device (33, 34) connected to the DC intermediate circuit (48) by means of the current collector system (38, 37, 42, 36, 35), the internal combustion engine (10) and the electric machine are switched off and the clutches (K1, K2) are preferably disengaged.

13. Track-mounted construction machine (1, 40) according to one of claims 1 to 3, characterized in that for charging a power storage device (33, 34) connected to the DC intermediate circuit (48) with the internal combustion engine (10) via the DC intermediate circuit (48), the switching clutch (K1) is engaged, the switching clutch (K2) is disengaged and the electric machine (30) operating in generator mode to generate power is connected to the DC intermediate circuit (48) via an inverter (43).

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