Drive system for feed harvester

Abstract

The present invention relates to a drive system for a feed harvester. The drive system for a self-propelled agricultural machine comprises: an electricity storage device (140); a DC-DC converter (146) connecting the electricity storage device (140) to the DC bus (128); an electric motor (112, 116) connected to the DC bus (128) by means of an inverter (132, 134); a first cooling circuit (182) for dissipating heat from the accumulator (140), the cooling liquid circulating through the first cooling circuit; a second cooling circuit (198) for dissipating heat of the coolant from the first cooling circuit (182), the refrigerant circulating through the second cooling circuit; and a third cooling circuit (206) for dissipating heat from the refrigerant from the second cooling circuit (198) and from the DC-DC converter (146) and the inverter (132, 134).

Description

Technical Field

[0001] The present invention relates to a drive system for a self-propelled agricultural machine. Background Art

[0002] Self-propelled agricultural machinery is increasingly being equipped with electric motors, which are powered entirely or partially by accumulators (batteries). Such machines can be designed as agricultural tractors or self-propelled harvesters. Electric drive systems offer higher efficiency than hydraulic drive systems (M. Gallmeier: "Electric Assembly Drives - an Alternative to Hydraulics?", Landtechnik 2007, pp. 266-267, and DE 202011002195 U1). Furthermore, a generator driven by the main drive system can power a battery, which is then used to power the generator during peak loads, thus acting as a motor (EP 1 563 724 A1). Alternatively, the battery can be used as an auxiliary or sole power source for the electric motor drive of the harvester's driven components, in addition to the motor-driven generator (EP 2 253 196 A1).

[0003] To store sufficient electrical energy, a correspondingly large accumulator is required. Similarly, the motor and generator must be sufficiently large. Consequently, air cooling is no longer sufficient to cool the accumulator, motor, and generator. Instead, powerful cooling systems are required to cool these relatively large components. Electric motors and generators are typically cooled with oil, while electronic components such as inverters and DC-DC converters are cooled with water, often with antifreeze added.

[0004] The problem of battery cooling remains unsolved. Liquid cooling arrangements have been described for this purpose, see WO 2017 / 067923 A1. However, conventional cooling systems for agricultural machinery are more likely to fail to achieve the typically expected operating temperature of conventional battery cells, which is below 40°C. Summary of the Invention

[0005] The invention is based on the object of avoiding at least some of these above-mentioned disadvantages.

[0006] The object of the present invention is achieved by a drive system for a self-propelled agricultural machine as described below.

[0007] A drive system for a self-propelled agricultural machine comprising:

[0008] accumulator;

[0009] a DC-DC converter connecting the battery to a DC bus;

[0010] an electric motor connected to the DC bus via an inverter;

[0011] a first cooling circuit for dissipating heat from the electrical storage device, a coolant circulating through the first cooling circuit;

[0012] a second cooling circuit for dissipating heat from the coolant of the first cooling circuit, a refrigerant circulating through the second cooling circuit; and

[0013] A third cooling circuit for dissipating heat from the refrigerant of the second cooling circuit and the DC-DC converter and inverter.

[0014] In other words, the DC-DC converter and inverter are cooled via a third cooling circuit, which also cools the second cooling circuit, which in turn cools the first cooling circuit for the battery. This three-stage cooling of the first cooling circuit has the advantage of allowing heat from the battery to be dissipated with minimal additional effort, namely for the first and second cooling circuits. The second cooling circuit allows for a sufficiently high temperature gradient between the third and first cooling circuits with acceptable efficiency, which firstly ensures a usable temperature for the battery and secondly allows the use of conventional cooling circuits for electronic components in agricultural machinery. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] An embodiment of the present invention will be explained based on the drawings, in which:

[0016] Figure 1 A schematic side view of a self-propelled forage harvester is shown,

[0017] Figure 2 A schematic top view of a drive system of a forage harvester is shown,

[0018] Figure 3 A schematic diagram showing the cooling of the electric motor and motor / generator for driving the feed roller and harvesting attachment, and

[0019] Figure 4 Schematic diagram showing battery cooling. DETAILED DESCRIPTION

[0020] Forage harvester

[0021] Self-propelled forage harvester 10 Figure 1. The forage harvester 10 is shown in a schematic side view. The forage harvester 10 is constructed on a frame 12 supported by driven front wheels 14 and steerable rear wheels 16. The forage harvester 10 is operated from a driver's cab 18, from which a harvesting attachment 20 in the form of a forager can be seen. The crops, such as grass, harvested from the ground by means of the harvesting attachment 20 are fed via a feed conveyor having a feed roller 22 arranged in a feed housing 24 on the front side of the forage harvester 10 to a chopping drum 26. The chopping drum is arranged below the driver's cab 18, chops the crops into small pieces, and discharges them to a further processing device having two grain handler rollers 38 and a conveyor device 28 following downstream (the grain handler rollers can be moved or moved to a spaced position when harvesting grass). The material leaves the forage harvester 10 to the accompanying transport vehicle through the discharge elbow 30, which is rotatable about a substantially vertical axis by an actuator, has an adjustable inclination and has a discharge flap that can be adjusted by an actuator. In the following, direction indications such as sideways, downward and upward refer to the direction of the forage harvester 10. Figure 1 The forward movement direction V is toward the right.

[0022] Figure 2 A top view of the drive arrangement of a forage harvester 10 is shown. In the rear region of the forage harvester 10 there is an internal combustion engine 36, in particular in the form of a diesel engine. The crankshaft 40 of the internal combustion engine 36 extends in the forward direction of the forage harvester 10. During operation, the crankshaft 40 of the internal combustion engine 36 drives a longitudinal shaft 44, which is connected to a first bevel gear 48 of a bevel gear transmission 52. The longitudinal shaft 44 also drives a pump unit 74 via gears 70, 72 and a second longitudinal shaft 76, which comprises a hydraulic pump for driving a hydraulic motor for the forward drive of the harvester, a steering pump, a pump 148 for supplying an actuator for adjusting the discharge elbow (see also FIG. 1 ). Figure 3 ) and a hydraulic pump for supplying oil to the control equipment of the hydrostatic drive for the forward drive of the harvester 10. It is also conceivable that other permanently driven parts, such as a generator for supplying power to the on-board power supply of the forage harvester 10 and / or a blower drive for supplying cooling air to the internal combustion engine 36, are driven by one of the gears 70, 72 or a gear arranged therebetween (not shown). The longitudinal shaft 76 is also in driving connection with a first motor / generator 124. This can be a conventional three-phase motor with internal permanent magnets. The first motor / generator 124 is electrically connected to a first inverter 126, which in turn is connected to a DC bus 128.

[0023] The second bevel gear 50 of the bevel gear transmission 52 is connected to a transverse shaft 80, which extends through a hollow shaft 106 connected to the pulley 82 on the side facing away from the bevel gear transmission 52 and is connected there to a clutch 78. On the output side, the clutch 78 is connected to the hollow shaft 106, which in turn drives a second motor / generator 102 on the side of the pulley 82 facing the bevel gear transmission 52 via gears 96, 108, and 100. The clutch 78 allows the drive belt 84, and thereby the cutting drum 26 and the conveyor 28, to be switched on and off. The clutch is disengaged and released by an actuator 122. The second motor / generator 102 is designed as a three-phase generator, similar to the first motor / generator 124, and is connected to a second inverter 130. The inverter 130 is in turn connected to a DC bus 128.

[0024] In addition, the DC bus 128 is connected to other inverters 132, 134, wherein the inverter 134 is connected to the first motor 112 that drives the feed roller 22 of the feed conveyor via the gear transmission mechanism 114, and the inverter 136 is connected to the second motor 116 (arranged on the forage harvester 10 or the harvesting attachment 20), which drives some, several or all of the driven components of the harvesting attachment 20. Figure 1 In the case of the picker shown in FIG, the motor 116 can drive the toothed roller 134, for example, and the transverse screw conveyor 138 can drive the feed roller 22 connected to the feed conveyor or be driven by another motor (not shown).

[0025] The electronic control unit 94 is connected for signal transmission to the operator interface 98, the inverters 126, 130, 132, 134, the clutch actuator 122, and the engine control unit 42 of the internal combustion engine 36. The DC bus 128 is connected to a rechargeable battery 140 (also designated as a dry cell or battery) via a DC-DC converter 146, which can be isolated from the DC bus 128 on the inlet or outlet side by a relay. The rechargeable battery is further connected to an external charging station via a charging device 142 and a charging socket.

[0026] Function

[0027] The control device 94 and the inverters 126, 130, 132, 134 function as follows: the control device 94 commands the bidirectional inverters 126, 130 to operate the first and second motor / generators 124, 102 as motors or generators, and to define the respective torques and / or speeds and the phase angles of the power consumption or power output on the shafts of the motor / generators 124, 102. In a similar manner, the control device 94 commands the equally bidirectional inverters 132, 134 to operate the motors 112, 116 as motors or generators, and to define the respective torques and / or speeds and the phase angles of the power consumption or power output on the shafts of the motors 112, 116. In other words, the motor / generator 124, 102 can be switched on by the control device 94 as a generator to charge the accumulator 140 and power the motors 112, 116 or brake the chopping drum 26, or can be switched on as a motor to drive the chopping drum 26 (for crushing) or accelerate (when starting) or use the internal combustion engine 36 as a brake to brake the chopping drum 26. In a similar manner, according to instructions from the control device 94, the motors 112, 116 can drive the feed roller 22 and the drivable parts of the harvesting attachment in motor operation and brake them in generator operation. The power flows through the DC bus 128.

[0028] Figure 1 and Figure 2 The drive arrangement shown is therefore configured to operate under the control of the control device 94 at least in the following operating modes:

[0029] (a) Accelerating the rotational speed of the chopping drum 26. To begin the harvesting operation, the internal combustion engine 36 must first be started, which can be started by the operator at their working position in the cab 18 using the ignition key or in other ways (e.g., via the operator interface 98). The clutch 78 is initially still disengaged, i.e., the chopping drum 26 is at rest. The operator can initiate the harvesting operation via the operator interface 98. To protect the clutch 78, the control device 94 causes the inverter 126 to operate the first motor / generator 124 as a generator to power the DC bus 128. Simultaneously, the control device 94 instructs the inverter 130 to operate the second motor / generator 102 as a motor, thereby accelerating the chopping drum 26. When the speeds at the input and output of the clutch 78 are approximately the same (the control device 94 is connected to appropriate sensors for detecting the speeds in a first section of the drive train of the shredder drum 26 upstream of the clutch 78 and in a second section of the drive train of the shredder drum 26 downstream of the clutch 78, or these speeds can be derived from signals provided directly by the motor / generators 124, 102 or by the inverters 126, 130 using current flowing through the motor / generators 124, 102), the clutch 78 is engaged and the second motor / generator 102 can be commanded to stop accelerating the second section of the drive train of the shredder drum 26. By this operating procedure, the clutch 78 is subjected to relatively light loads and has a longer service life than if it were engaged when the shredder drum 26 is stationary.

[0030] (b) Harvesting Operation. During normal harvesting operation, the internal combustion engine 36 drives the chopping drum 26 and the conveyor 28 via two sections of the drive train, which are connected by a clutch 78. The first motor / generator 124 operates as a generator and supplies electrical energy to a DC bus 128, which in turn is used to power the electric motors 112 and 116 that drive the feed roller 22 and the drivable components of the harvesting attachment 20. The electric motors 112 and 116 are activated in response to corresponding operator input via the operator interface 98. The second motor / generator 102 can also operate as a generator during harvesting operation and supply power to the DC bus 128, or it can idle without discharging or consuming power. In addition, as needed, as explained further below, the accumulator 140 can provide additional energy for the electric motors 112 and 116, or, in special circumstances associated with high loads on the chopping drum 26 and / or the conveyor 28, for the first and / or second motor / generators 124 and 102. It may be advisable to use the first motor / generator 124 rather than the second motor / generator 102 to convert the mechanical energy provided by the internal combustion engine 36 into electrical energy, because the clutch 78 is not loaded here, while the second motor / generator 102 is used for operating conditions where the chopping drum 26 and / or the conveying device 28 have to have the mechanical energy supplied.

[0031] The speed of the motor 112, together with the speed of the chopping drum 26, determines the crop cutting length. This can be predefined by the operator via the operator interface 98, or sensors detect crop properties and define the cutting length and, in turn, the speed of the motor 112, which is controlled by the control device 94 and the inverter 132. The speed of the motor 116 can be fixed or predetermined or depend on the cutting length and / or the forward drive speed of the forage harvester 10 (see EP 1 609 351 A1).

[0032] (c) After the harvesting operation or in the event of an interruption, it is desirable to stop the chopping drum 26 in order, firstly, to avoid the risk of accidents and, secondly, to reduce noise. To this end, in response to appropriate operator input to the operator interface 98 or other sensor-based detection of non-harvesting conditions, such as when the operator leaves his seat, after the clutch 78 has been disengaged, the second motor / generator 102 operates as a generator and converts the rotational energy of the chopping drum 26 and the conveyor 28 into electrical energy, which is supplied to the accumulator 104 via the DC bus 128 and, particularly if the DC bus is sufficiently charged, supplies the electrical energy to the first motor / generator 124, which operates as a motor and actively drives the internal combustion engine 36, thereby performing engine braking as a result of cylinder-piston compression action and friction to convert the rotational energy of the chopping drum 26 into heat.

[0033] (d) Alternatively, the second motor / generator 102 can be used in conjunction with the clutch 78, which is disengaged to drive the chopping drum 26 to crush at a speed and / or direction of rotation that is altered relative to the harvesting operation. The second motor / generator 102 then operates as a motor and is powered by the battery if the internal combustion engine 36 is stopped, or by the power supplied by the first motor / generator 124 if the internal combustion engine 36 is running. In this regard, reference is made to DE 10 2018 211 863 A1, the entire disclosure of which is incorporated herein by reference.

[0034] (e) Forage harvester 10 is also equipped with a foreign object detector 144, which can be designed as a metal detector and / or a stone detector for detecting impacting stones and can be installed in the front upper feed roller 22. When foreign object detector 144 responds, the control device 94 connected thereto receives a corresponding signal and causes electric motor 112 to stop. The latter then operates as a generator, and the generated electricity is transmitted via DC bus 128 to first motor / generator 124, which converts the electricity into heat via internal combustion engine 36, similar to operating mode (c). Engine 116 is also stopped in this manner.

[0035] (f) So far, so-called hybrid electric operation has been described, in which the internal combustion engine 36 drives the motor / generator 124, 102 during harvesting, which in turn supplies power to the electric motors 112, 116. In principle, the battery 140 is unnecessary and can be omitted. However, the advantage of the battery 140 is that it can at least temporarily increase the total drive output of the forage harvester 10. Therefore, so-called battery operation of the forage harvester 10 is also provided.

[0036] For battery operation, hybrid electric operation is first switched on. The accumulator 140 can be added via an input on the operator interface 98 . To this end, the voltage state of the accumulator 140 is read by the control device 94 . A voltage equal to the current voltage of the accumulator 140 is preset to the inverter 126 of the first motor / generator 124 to achieve a state in which minimal current flows to the DC bus 128 when the accumulator 140 is connected. Once this state has been reached, the relay of the DC-DC converter 146 connected to the accumulator 140 is switched on. The feed roller 22 and the components of the harvesting attachment 20 driven by the electric motor 116 can then be powered directly and exclusively (or at least partially, depending on their respective power requirements) by the accumulator 140. The power previously provided by the internal combustion engine 36 is then free and can be used for other purposes, in particular for driving the chopping drum 26.

[0037] In battery operation, the first motor / generator 124 functions as a generator, but does not supply power to the electric motors 116, 118 during harvesting operation (depending on the yield and power requirements). This is then drawn solely from the battery, or partially from the battery. If the forage harvester requires only relatively little power, for example, when in uncultivated fields or during a transport journey, the control device 94 supplies a higher voltage to the first motor / generator 124 than is supplied from the accumulator 140, causing current to flow into the accumulator and allowing it to be charged. In principle, charging takes place during idling, when in uncultivated fields, and during transport.

[0038] Furthermore, even during harvesting operations, under low load, the battery 140 can be charged by the first motor / generator 124 by increasing its target voltage. This can be used primarily to shift the load point of the internal combustion engine 36 to a higher efficiency point in the fuel consumption characteristic curve. As a result, the overall efficiency of the forage harvester 10 is improved, and less CO2 is emitted.

[0039] By electrically driving the harvesting attachment 20 with the electric motor 116, the power drawn by the motor can be permanently measured as a measure of yield. If a portion of the field is densely packed, an increased power demand may be detected at the harvesting attachment 20. In order to maintain the permitted speed without causing the forage harvester 10 to jam, a predetermined speed value can be sent to the inverter 126 of the first motor / generator 124. This results in the internal combustion engine 36 being accelerated by the additional torque from the first motor / generator 124, using energy from the accumulator 140, without causing a malfunction. Additionally or alternatively, the second motor / generator 102 upstream of the clutch 78 can also be used to maintain the speed of the chopping drum 26, as already mentioned above.

[0040] It should also be noted that a number of variations of the illustrated embodiment are conceivable. Thus, the drive of the wheels 14, 16 could also be performed by a plurality of electric motors, instead of being performed by hydrostatic drives, each of which is connected to the DC bus 128 via an inverter and controlled by the control device 94. In this case, the electric motors can jointly drive the wheels 14 or 16 of the front and / or rear axle via a gearbox, or the wheels can be driven individually, in particular via wheel hub motors. Similarly, the drive of the fans of the main cooling assembly can be electrified. For this purpose, a single central electric motor for driving the fans of all coolers is conceivable, as well as a fan array with a plurality of electric motors and fans, which ventilate the individual coolers under application and temperature control.

[0041] Furthermore, the drive of the grain handler rollers 38 can be effected by one or two electric motors which are connected to the DC bus 128 in a similar manner to the motors 112, 116. Reference is also made here to DE 102021113626 A1, DE 102018205221 A1 and DE 102013110636 A1, the entire disclosures of which are incorporated herein by reference.

[0042] Finally, it should also be noted that operating mode (e) is not dependent on the presence of the second motor / generator 102 and can also be used in a forage harvester 10 that does not have this second motor / generator 102. This applies similarly to stopping the feed roller 22 and the driven components of the harvesting attachment 20 when the foreign object detector 144 responds in operating mode (e). The details discussed so far can also be found in DE 10 20 23 13 5 106 A1, the disclosure of which is incorporated herein by reference.

[0043] Cooling of electric motors and motor / generators

[0044] Figure 3It is shown how the cooling of the electric motors 112, 116 and the motor / generators 102, 124 is carried out. Hydraulic fluid is taken from a hydraulic oil tank 148 by a pump 150, which can be part of the pump unit 74, and supplied to a valve block 150. The latter comprises an outlet 152 directly connected to its inlet 154, to which other hydraulically actuated components, such as actuators for adjusting the discharge elbow 30 or for driving a rotary cleaning screen for the cooling air, can be connected.

[0045] The valve group 150 also includes a plurality of throttle valves 156 to 170, each of which is connected on the inlet side to the inlet 154 and on the outlet side to one of the electric motors 112, 116 or motor / generators 102, 124. Thus, each electric motor 112, 116 and motor / generator 102, 124 receives two flows of hydraulic fluid via associated lines 172, 174. In any case, one of these lines 172 directs the hydraulic fluid to the stator of the electric motor 112, 116 or motor / generator 102, 124, and the other line 174 directs it to the rotor of the electric motor 112, 116 or motor / generator 102, 124.

[0046] The electric motors 112, 116 and the motor / generators 102, 124 also each comprise an outlet connected via respective lines 176 to a return tank 178. From there, the hydraulic fluid preferably flows back under no pressure to the hydraulic oil tank 148. The latter is also connected to an oil cooler 180 which is cooled by a flow of air in order to reduce the temperature of the hydraulic fluid.

[0047] Cooling of storage devices and power electronics

[0048] The battery 140 is also equipped with Figure 4 The cooling is schematically shown. The battery 140 can be as Figure 4 As shown, the battery is divided into two or more units, which offers advantages such as modular expandability and interchangeability. Due to the high output during charging and discharging of one or more battery cells 140, a certain amount of heat loss occurs, which must be dissipated. Furthermore, at low temperatures, it may be desirable to warm up the battery cells 140. The temperature of the battery cells 140 is therefore controlled by a dielectric (non-conductive) coolant that flows around the individual cells of the battery cells 140 (see WO 2017 / 067923 A1).

[0049] The dielectric coolant circulates in a first circuit 182. An expansion tank 184 can hold a certain amount of dielectric coolant. A first coolant pump 186 delivers the dielectric coolant via a line 188 to an adjustable bypass valve 190, from which a portion of the dielectric coolant is directed directly to a filter 194 and a portion is directed to the filter 194 via a first heat exchanger 192. The filter 194 is connected on its outlet side to the inlet of the battery 140, which in turn is connected to the expansion tank 184 and the inlet of the first coolant pump 186. In this way, the first coolant pump 186 influences the circulation of the dielectric coolant around the multiple cells of the battery 140, wherein the portion of the dielectric coolant directed through the first heat exchanger 192 can be varied via the adjustable bypass valve 190.

[0050] The heat from the dielectric coolant is dissipated via the first heat exchanger 192, which is cooled via the second circuit 198. In addition to the first heat exchanger 192, it also includes a compressor 200, a second heat exchanger 202, typically embodied as a plate heat exchanger, and an expansion valve 204. The second circuit 198 thus operates as a heat pump, as the compressor 200 compresses the refrigerant (e.g., a refrigerant commonly used in heat pumps or air conditioning systems) heated in the first heat exchanger 192 and circulating in the second circuit 198, and no longer heats the refrigerant, so that the heated refrigerant transfers its heat to the third cooling circuit 206 in the second heat exchanger 202. The pressure of the now cooler refrigerant is reduced again in the expansion valve 204.

[0051] The third cooling circuit 206 includes a second coolant pump 210, which is connected on its inlet to the outlet of the cooler 208 through which air flows. The air flow through the cooler 208 is generated by a blower 218. The inlet of the second coolant pump 210 is also connected to the expansion tank 212. On its outlet, the second coolant pump 210 is connected to a bypass valve 216. Its first outlet is connected via a pipeline to the second heat exchanger 202 and to the inverters 126, 130, 132, and 134 (or to channels on or in the inverter heat sink to cool their electronic components, see, for example, WO 2016 / 094059 A1). These outlets are also connected via pipelines to the inlet of the cooler 208. The second outlet of the bypass valve 216 is connected to the charging device 142 (in series in the embodiment shown for the coolant), and to the DC-DC converter 146, whose outlet is in turn connected to the cooler 208. The third cooling circuit 206 may utilize water with an antifreeze agent (e.g., ethylene glycol) as a coolant, for example. The coolant is supplied by a second coolant pump 210 as needed through a bypass valve 216 to the charging device 142, the DC-DC converter 146, the inverters 126, 130, 132, 134, and the cooler 208.

[0052] The electronically adjustable speeds of the coolant pumps 186, 210 and also the compressor 200 can be controlled by the control device 94 based on sensors for detecting the temperatures of the coolant and refrigerant in the three cooling circuits 182, 198, 206 (or based on the temperature of the components to be cooled). In a similar manner, the bypass valves 190 and 216 can also be controlled by the control device 94.

Claims

1. A drive system for a self-propelled agricultural machine, the drive system comprising: accumulator (140); a DC-DC converter (146) connecting the battery (140) to a DC bus (128); an electric motor (112, 116), the electric motor (112, 116) being connected to the DC bus (128) via an inverter (132, 134); a first cooling circuit (182), the first cooling circuit (182) being used to dissipate heat from the battery (140), and a coolant circulating through the first cooling circuit; a second cooling circuit (198) for dissipating heat from the cooling fluid of the first cooling circuit (182), through which refrigerant circulates; and A third cooling circuit (206) is provided for dissipating heat from the refrigerant of the second cooling circuit (198) and the DC-DC converter (146) and the inverter (132, 134).

2. The drive system according to claim 1 , comprising an internal combustion engine (36) and a motor / generator (102, 124) which can be brought into transmission engagement with the internal combustion engine (36) and connected to the DC bus (128) by means of a DC-DC converter (126, 130), wherein: The DC-DC converter (126, 130) of the motor / generator (102, 124) can be cooled by the third cooling circuit (206).

3. The drive system according to claim 1 or 2, wherein: The second cooling circuit (198) comprises a heat pump.

4. A drive system according to any one of the preceding claims, wherein: Heat from the third cooling circuit (206) can be rejected to the ambient air via a cooler (208).

5. The drive system according to claim 4, wherein: The cooler (208) has an air flow supplied to the cooler (208) by a blower (218).

6. A drive system according to any one of the preceding claims, wherein: The second cooling circuit (198) and the third cooling circuit (206) are thermally connected via a second heat exchanger (202).

7. A drive system according to any one of the preceding claims, wherein: The first cooling circuit (182) and the second cooling circuit (198) are thermally connected via a first heat exchanger (192).

8. The drive system according to any one of claims 3 to 7, wherein: The second cooling circuit (198) includes a compressor (200) between the first heat exchanger (192) and the second heat exchanger (202) and an expansion valve between the second heat exchanger (202) and the first heat exchanger (192).

9. The drive system according to any one of claims 2 to 8, wherein: The electric motor (112, 116) and the motor / generator (102, 124) are cooled by the hydraulic flow of the self-propelled agricultural machine.

10. A machine, in particular a harvester, preferably a forage harvester (10), having a drive system according to any one of claims 1 to 9.

Images