Drive device for a working machine

Abstract

The present disclosure relates to a drive device for a working machine. A fuel cell unit (13) is configured to operate the drive device and to provide excess fuel cell energy. A working unit (36) is configured to perform a work task of the working machine. A working pump (32) is configured to provide a pressurized fluid at least at a pressure level for the working unit (36). The working pump (32) can be operated by the fuel cell energy of the fuel cell unit (13). A fluid storage unit (12) is configured to store the pressurized fluid of the working pump (32) and to discharge the pressurized fluid at the pressure level for the working unit (36) as load point reduction energy. The working unit (36) can be operated via the load point reduction energy.The operating power of the fuel cell unit (13) can be increased by operating the working pump (32) with the excess fuel cell energy from the fuel cell unit (13). The operating power of the fuel cell unit (13) can be reduced by supplying the load point reduction energy to operate the working unit (36) via the fluid storage unit (12).

Description

Technical field

[0001] The present invention relates to a drive device and a working machine with a drive device. State of the art

[0002] Drive devices for working machines are known. Such a drive device can include a fuel cell for providing electrical energy to operate the working machine. The working machine exhibits operating conditions for which the fuel cell must operate at a low efficiency, for example, during braking. With a rapid change in the operating condition, the operating point of the fuel cell must be changed accordingly. This accelerates the aging process of the fuel cell. DE 10 2013 103 949 A1 discloses a working machine with a fuel cell that drives a hydraulic pump via an electric drive motor and an energy storage device. The working machine includes a Stirling engine for driving a generator, which also supplies current to the electrical energy storage device. DE 10 2008 012 406 A1 discloses another working machine with a fuel cell. Description of the invention

[0003] The object of the present invention is to provide an improved drive device. This object is achieved with a drive device having the features of claim 1. Advantageous further developments are the subject of the dependent claims.

[0004] In the first aspect, a drive device for a working machine is provided. The drive device can be configured to move the working machine. For example, the housing of the drive device can be attached to a stationary component of the working machine, such as a vehicle frame. The working machine can be a construction or agricultural machine, such as a wheel loader, excavator, dump truck, crane, or tractor. The drive device includes a fuel cell unit, a working unit, a working pump, an energy storage unit, and a fluid storage unit. The fuel cell unit is configured to power the drive device and to provide excess fuel cell energy. The working unit is configured to perform a work task for the working machine.The working pump is configured to supply a pressurized fluid at least at a pressure level suitable for the working equipment. The working pump can be operated using the fuel cell energy of the fuel cell system. The fluid storage system is configured to store the pressurized fluid from the working pump and to deliver the pressurized fluid to the working equipment at the pressure level suitable for load reduction. The working equipment can be operated at least via the pressurized fluid from the fluid storage system. The working equipment can also be operated directly via the pressurized fluid from the working pump.

[0005] The operating power of the fuel cell system can be increased by operating the working pump with the excess fuel cell energy. Conversely, the operating power of the fuel cell system can be reduced by supplying the load-point reduction energy to operate the working equipment via the fluid storage system. The fuel cell energy can be electrical. The load-point reduction energy can be fluid energy, such as hydraulic energy. The drive system can include several consumers, such as the working pump, a working motor to drive the working pump, and a traction motor to move the working machine. The consumers can have an energy demand, such as a power requirement for a specific period. This energy demand can be electrical, hydraulic, or a combination thereof.

[0006] The fuel cell system can include a fuel cell and a hydrogen storage system. Furthermore, the fuel cell system can include components such as a compressor, a fan, and other elements. The fuel cell can generate electrical energy, for example, electrical power for a specific period, from hydrogen and oxygen. Water may be produced in the process. The fuel cell system can have a nominal operating range with high efficiency. Within this nominal operating range, the fuel cell system can provide a specific amount of electrical energy, for example, electrical operating power, for a specific period. Within this nominal operating range, the fuel cell system can provide a specific amount of nominal energy, for example, a nominal electrical power, for a specific period.The fuel cell system can be operated in a throttled operating range. In the throttled operating range, the fuel cell system can provide less electrical energy than in the nominal operating range. However, the efficiency may be low in the throttled operating range. The fuel cell system can also be operated in an over-proportioned operating range. In the over-proportioned operating range, the fuel cell system can provide more electrical energy than in the nominal operating range. However, the efficiency may be low in the over-proportioned operating range.

[0007] The operating power of the fuel cell system can be increased by using excess fuel cell energy to operate the working pump. Conversely, the operating power of the fuel cell system can be reduced by using the load-point reduction energy of the fluid storage system. Therefore, the working pump and the fluid storage system can enable the fuel cell system to operate within its nominal operating range, even if the energy demand of the drive system differs from the nominal energy of the fuel cell system.

[0008] If two elements are mechanically connected, they are coupled to each other directly or indirectly in such a way that a movement of one element causes a reaction of the other. For example, a mechanical connection can be provided by a positive-locking or friction-locking connection. The mechanical connection can correspond to the meshing of corresponding gear teeth on the two elements. Further elements, such as one or more spur gear stages, can be provided between the elements. A permanently rotationally fixed connection between two elements, on the other hand, is understood to be a connection in which the two elements are rigidly coupled to each other in all intended states. The elements can be individual components connected in a rotationally fixed manner or even as a single piece.However, a switching element, such as a clutch or brake, can be used to selectively establish or break a rotationally fixed connection between two elements.

[0009] The drive device can comprise at least one traction transmission, a first traction switching element, and a second traction switching element. The traction transmission can have an input element and an output element. The input element of the traction transmission can be mechanically operatively connected to the output element of the traction transmission. The drive shaft of the traction motor can be rotationally fixed to the input element of the traction transmission. The traction transmission can provide different gear ratios between the input element and the output element. The different gear ratios can be selected via the first traction switching element, the second traction switching element, or both the first and second traction switching elements. The traction transmission can comprise a first spur gear transmission and a second spur gear transmission.At least one of the first spur gear unit and the second spur gear unit can be designed as a three-stage spur gear unit. The output element of the traction transmission can be rotationally fixed to the traction element.

[0010] The drive unit can provide various driving states, such as downhill travel, uphill travel, braking, travel on level ground, coasting without traction, acceleration, and work processes for the machine. The fluid can be hydraulic oil. The fluid can be a working gas, such as air. The working unit can include at least one lifting device, one lowering device, and one gripping device. The working unit can be configured to lift, lower, and / or grip a load as its work task. The working unit can be operated via the fluid storage device to perform its respective work task. The working unit can be operated directly via the working pump.

[0011] The working pump can provide a fluid output. The fluid output can have a fluid volume and a fluid pressure. The working pump can be designed for a variable fluid output, for example, a variable flow rate and / or a variable fluid pressure. The working pump can provide a fluid output with a fluid pressure that is necessary to operate the working equipment or higher. The drive device can have a control element, for example, a control lever, by which a desired fluid output of the working pump can be set. For example, the fluid output of the working pump can be designed to operate the working equipment.

[0012] The pump can be designed as a vane pump, gear pump, or axial piston pump. The pump can have a swashplate for adjusting the fluid output. The pump can have an inlet element for driving the pump. The fluid output can be adjusted via the rotational speed of the inlet element. The fluid output can be adjusted via the swashplate's angle of rotation. A large swashplate angle and / or a large rotational speed of the pump's inlet element can provide a high fluid output. With a large swashplate angle, the pump typically exhibits a comparatively high efficiency. The pump can be operated within a nominal operating range to achieve a high fluid output.

[0013] During driving conditions with low or no energy demand, such as recuperation, braking, or coasting, there may be little or no energy required, for example, electrical energy, to propel the machine. The fuel cell system can still operate within a favorable operating range, such as one with high efficiency. In this case, excess electrical energy, such as fuel cell energy, can be supplied by the fuel cell system. This fuel cell energy can then be used to power the pump. Furthermore, the drive system can include an energy storage device designed to store the excess electrical energy from the fuel cell system.Therefore, the supply of electrical energy to the fuel cell system does not need to be reduced, and the fuel cell system does not need to be throttled.

[0014] The fluid storage device can be configured to store the fluid output of the working pump. It can also be configured to store a quantity of fluid at a specific or variable, for example, adjustable, fluid pressure. This allows the fluid storage device to store fluid energy, such as hydraulic energy. The fluid storage device can have a variable volume. This variable volume can be pressurized, for example, via a pre-tensioning element. The pre-tensioning element can be a pneumatic or mechanical spring element. The fluid storage device can have a charge state. The storage capacity, for example, the quantity of pressurized fluid per unit of time that can be stored in the fluid storage device, can depend on this charge state.For example, the storage capacity may be limited when the state of charge is high, such as 75% or higher. The storage capacity may be zero when the state of charge is very high, such as 95% or higher. A withdrawal capacity, such as the amount of pressurized fluid that can be drawn from the fluid storage device per unit of time, may be limited when the state of charge is low, such as 5% or lower. The working device may be powered by the fluid energy drawn from the fluid storage device. The fluid energy drawn from the fluid storage device may constitute load point reduction energy. The load point reduction energy may be used to assist the fuel cell device in operating the drive device.

[0015] This allows for the provision of an additional storage device through which the fuel cell energy can be stored in the form of fluid energy. This means that the fuel cell energy can be stored even when the energy storage device itself is already full. The working pump can operate within its nominal operating range to store the fuel cell energy as fluid energy, even when the energy storage device is full. This allows the working pump to operate with high efficiency to store the fuel cell energy as fluid energy. By generating the fuel cell energy, the fuel cell system can operate within its optimal operating range during recuperation, braking, and coasting without throttling the fuel cell system.

[0016] During a driving condition with high energy demand, such as during a work process, there may be a need for increased energy, for example, electrical energy, to propel the machine and / or perform its task. The fuel cell system can still operate within its optimal operating range. Additional fluid energy, such as load point reduction energy, can be provided via the fluid storage system, for example, to support the fuel cell system. This load point reduction energy can be hydraulic. The additional fluid energy can be used to perform the task in addition to the electrical energy from the fuel cell system. Therefore, the electrical energy supply to the fuel cell system does not need to be excessive, and the fuel cell system does not need to be operated in an unfavorable operating range.

[0017] In one embodiment of the drive device, the drive device can include a traction motor for propelling the working machine. The fuel cell unit can be configured to operate the traction motor. The traction motor can be configured to brake the working machine. The traction motor can also be configured to generate recuperated energy. The fuel cell unit can be electrically connected to the traction motor. The traction motor can be operated using the electrical energy generated in the fuel cell unit. The traction motor can be designed as an electric motor. The traction motor can be configured to drive at least one traction element of the vehicle. The traction motor can have a drive shaft. The traction motor, for example, the drive shaft of the traction motor, can be mechanically connected to the traction element.The traction element can comprise at least one drive wheel, one drive axle, one driven axle unit, and one tracked undercarriage. This allows the traction motor to be configured for propelling the vehicle.

[0018] In one embodiment of the drive device, the traction motor can be configured to generate recuperated energy. The working pump can be powered by the recuperated energy from the traction motor. The traction motor can have a recuperation mode in which it can operate as a generator. In this mode, the traction motor can generate electrical recuperated energy and simultaneously provide braking force for the driven machine. The recuperated energy can be stored in the energy storage device. The drive device can thus incorporate the recuperation process as a driving state. A long-lasting recuperation process can be implemented during downhill driving. A short-lasting recuperation process can be implemented during braking, for example, to reduce the speed of the driven machine. The driven motor can be powered by the recuperated energy from the traction motor.This allows the working pump to be operated using recuperated energy.

[0019] The fluid storage system can be designed to store recuperated energy in the form of fluid energy. This allows the recuperated energy to be stored even when the energy storage system is already full. The working pump can also be operated within its nominal operating range to store the recuperated energy as fluid energy, even when the energy storage system is full. This allows the working pump to operate with high efficiency while storing the recuperated energy as fluid energy.

[0020] The drive device may include an energy conversion unit, for example, a brake chopper or a braking resistor. The energy conversion unit may be designed to convert at least one of the excess recuperation energy and excess fuel cell energy into thermal energy. The excess recuperation energy and the excess fuel cell energy may each constitute energy that cannot be stored or used as either fluid energy or electrical energy.

[0021] In one embodiment of the drive device, the drive device can include a working motor for driving the working pump. The working motor can be designed as an electric motor. The working motor can be powered by the electrical energy, for example, the energy from the fuel cell unit. The working motor can be powered by the electrical energy stored in the energy storage unit. The working motor can have a drive shaft. The input element of the working pump can be mechanically connected to the drive shaft of the working motor. The drive device can include a working gearbox. The working gearbox can be designed as a two-stage spur gear unit. The working gearbox can have an input element and an output element. The input element can be mechanically connected to the output element, for example, via a gear mesh.The input element of the working gearbox can be non-rotatably connected to the drive shaft of the working motor. The output element of the working gearbox can be non-rotatably connected to the input element of the working pump for operating or driving the working pump.

[0022] In one embodiment of the drive device, the drive device can include an energy storage device for storing at least the fuel cell energy and for providing electrical load-point reduction energy to operate the working motor. The energy storage device can be configured to store electrical energy. The energy storage device can be configured as a battery. The energy storage device can have a state of charge. A charging power, for example, the amount of electrical energy per unit of time that can be stored in the energy storage device, can depend on the state of charge. For example, a charging power can be limited when the state of charge is high, for example, 75% or higher. The charging power can be zero when the state of charge is very high, for example, 95% or higher.The discharge power, for example, the amount of electrical energy per unit of time that can be drawn from the energy storage device, may be limited when the state of charge is low, for example, 5% or less. The energy storage device may be electrically connected to the traction motor. The energy storage device may be electrically connected to the working motor. The energy storage device may be designed to drive at least one of the traction motors and the working motor, for example, using the electrical energy stored in the energy storage device.

[0023] In one embodiment of the drive device, the working pump can be fluidically connected to the fluid storage device. The fluid storage device can be fluidically connected to the working device via a first valve. If two elements are fluidically connected to each other, a fluid, for example, oil, can be conveyed from one element to the other. The fluid connection can be designed to be leak-free, so that the oil is conveyed essentially completely from one element to the other. The fluid connection can be configured as a channel, a pipe, a hose, or the like. The fluid connection can also be designed as a direct fluid connection without any additional elements between the fluidically connected elements.The fluid connection can be designed as an indirect fluid connection via additional elements between the fluidically connected elements.

[0024] The first valve can be configured as a check valve, pressure relief valve, multi-way valve, and / or control valve. The first valve can be electrically, hydraulically, and / or pneumatically controlled. The fluid storage device can be directly connected to the first valve. The first valve can be directly connected to the working device. The working pump can be connected to the working device via the first valve. The working pump can be directly connected to the first valve.

[0025] In one embodiment of the drive device, the working pump can be fluidically connected to the fluid storage device via a second valve. The fluid storage device can be fluidically connected to the first valve via the second valve. The second valve can be configured as a check valve, pressure relief valve, multi-way valve, and / or control valve. The second valve can be electrically, hydraulically, and / or pneumatically controlled. The working pump can be fluidically connected directly to both the first and second valves. The second valve can be fluidically connected directly to the fluid storage device. Filling or withdrawing fluid from the fluid storage device can be controlled via the second valve. The second valve can be fluidically connected directly to the first valve.

[0026] In one embodiment of the drive device, the drive device can include a system pump for supplying a pressurized fluid at least at a pressure level suitable for system elements of the drive device. The working motor can be configured to drive both the system pump and the working pump. The working pump and the system pump can share a common drive shaft for being driven by the working motor. System elements can be configured, for example, as gears that may mesh with each other, as switching elements, as bearing units, or the like. The system pump can, for example, be configured to supply a pressurized fluid for actuating, lubricating, and / or cooling the system elements.

[0027] The system pump can provide a fluid output. The fluid output can have a fluid volume and a fluid pressure. The fluid pressure can correspond to the fluid pressure of the output of the working pump. The system pump can be designed for a variable fluid output, for example, a variable flow rate and / or a variable fluid pressure. The system pump can provide a fluid output with a fluid pressure that is necessary for operating the system components or higher. The system pump can be designed as a vane pump, gear pump, or axial piston pump. The system pump can have a swashplate for adjusting the fluid output. The system pump can have an inlet element for operating or driving the system pump. The inlet element of the system pump can be mechanically connected to the drive shaft of the working motor.The inlet element of the system pump can be non-rotatably connected to the inlet element of the working pump. The inlet element of the system pump and the inlet element of the working pump can form a common drive shaft, for example, as a single piece.

[0028] In a second aspect, a method for operating a drive device according to one of the preceding embodiments is provided. Further features, effects, and advantages for the second aspect can be derived from the first aspect. Furthermore, features, effects, and advantages of the second aspect also represent features, effects, and advantages for the first aspect. The method comprises, in a first step, providing fuel cell energy via the fuel cell device. The method comprises, in a further step, operating the working pump to provide pressurized fluid at least at a pressure level for the working device using the fuel cell energy. The method comprises, in a further step, storing the pressurized fluid of the working pump in the fluid storage device.The procedure includes, in a further step, operating the working equipment with a load point reduction energy output by the fluid storage device.

[0029] The provision of fuel cell energy can depend on the state of charge of the energy storage device and / or the fluid storage device. The provision of load point reduction energy can also depend on the state of charge of the fluid storage device. Load point reduction energy can be related to the charging power of the energy storage device and / or the storage power of the fluid storage device. For example, if the fluid storage device has a high state of charge, the load point reduction energy can be throttled. Load point increase power can depend on the state of charge of the energy storage device and / or the fluid storage device. Load point increase power can be related to the charging power of the energy storage device and / or the storage power of the fluid storage device.For example, if the energy storage device and / or the fluid storage device has a high state of charge, the load point boosting power can be throttled.

[0030] Furthermore, the process can include energy recuperation via the traction motor in a further step. For recuperation, the traction motor can be operated in recuperation mode. The recuperation power can depend on the state of charge of the energy storage device and / or the fluid storage device. It can also be related to the charging power of the energy storage device and / or the storage power of the fluid storage device. For example, if the energy storage device and / or the fluid storage device has a high state of charge, the recuperation power can be throttled. Furthermore, the process can be configured in a further step to convert at least some of the excess fuel cell energy and excess recuperation energy into heat energy via the energy conversion device.Furthermore, the process can, in a further step, include operating the working pump to provide the pressurized fluid using the recuperation energy.

[0031] In one embodiment of the method, the provision of fuel cell energy can be carried out at least when the requested power for the drive device is less than the rated power of the fuel cell unit. Alternatively or additionally, the provision can be carried out when a requested power reduction for the drive device exceeds the power variability of the fuel cell unit. The requested power can be related to a driving condition. When changing from a driving condition to one with lower energy demand, for example, during braking, a power reduction for the drive device may be requested. When changing from a driving condition to one with higher energy demand, for example, during a work process, an increase in power for the drive device may be requested.The requested power reduction and the requested power increase can include a power change rate. The power change rate can specify a time period within which the requested power reduction or the requested power increase should be executed. If the requested power falls below the rated power of the fuel cell system, for example during power reduction, excess fuel cell energy can be generated by the fuel cell system. In this case, the fuel cell system can still operate with high efficiency within its rated operating range.

[0032] The fuel cell system can exhibit power variability. This power variability refers to the fuel cell system's ability to change the electrical power output it provides within a specific time period. If the required power variability rate during a power reduction is greater than the fuel cell system's power variability, excess fuel cell energy can be generated. In this case, the fuel cell system can still operate with high efficiency within its nominal operating range.

[0033] In one embodiment of the method, operating the working device with the load point reduction energy can be carried out at least when the required power for the drive device is greater than the rated power of the fuel cell device. Alternatively or additionally, operation can be carried out when a required power increase for the drive device exceeds the power variability of the fuel cell device. If the required power, for example during the required power increase, exceeds the rated power of the fuel cell device, fluid energy, such as the load point reduction energy, can be provided via the fluid storage device, for example to support the fuel cell device. In this case, the fuel cell device can still be operated with high efficiency in the rated operating range.If the required rate of power change during a requested power increase exceeds the power change capability of the fuel cell system, fluid energy, such as load point reduction energy, can be provided via the fluid storage system, for example, to support the fuel cell system. In this case, the fuel cell system can still operate with high efficiency within its nominal operating range.

[0034] A third aspect includes a control device. Further features, effects, and advantages of the third aspect can be derived from one of the preceding aspects. Furthermore, features, effects, and advantages of the third aspect also represent features, effects, and advantages for one of the preceding aspects. The control device is configured to execute a method according to an embodiment of the second aspect. The control device may have an input interface and an output interface. The input interface and the output interface may each be configured to transmit electrical signals. The input interface may be configured to receive system information from the drive device, for example, the charge level of the energy storage device and / or the fluid storage device.The input interface can be configured to receive control signals from control elements such as the control lever. The output interface can be configured to output signals for controlling components of the drive system, such as the traction motor, the working motor, and the working pump.

[0035] The control unit can be configured to detect at least one of the recuperation process, the braking process, the coasting process, and the operating process of the drive device. The control unit can include a hydraulic control unit for controlling at least one of the first and second valves. The hydraulic control unit can be configured so that, optionally, the fluid output of at least one of the working pumps and the system pump can be stored in the fluid accumulator, or a fluid output can be drawn from the fluid accumulator. The hydraulic control unit can be configured so that, when a recuperation process, a braking process, or a coasting process is present, the fluid output of at least one of the working pumps and the system pump can be stored in the fluid accumulator.The hydraulic control unit can be configured so that the working device can be operated during a work process either via fluid output from the fluid storage device (e.g., via the load point reduction energy), or from the working pump, or a combination thereof. The hydraulic control unit can be configured so that the storage capacity and / or the discharge capacity of the fluid storage device can be limited depending on the state of charge of the fluid storage device. The control unit can include a vehicle control unit for controlling an energy flow between at least one of the energy storage devices and the fuel cell device, and between at least one of the traction motor and the working motor.The vehicle control unit can be configured so that it is possible to select the generation of at least one recuperation energy and one fuel cell energy, or the driving of at least one of the traction motor and the working motor.

[0036] The control unit can include a drive control unit for controlling an inverter to provide electrical power for driving the working motor. The control unit can include a drive control unit for controlling at least one inverter to provide electrical power for driving at least one of the working motor and the traction motor. The drive control unit can be configured so that the charging and / or discharging power of the energy storage device can be limited, for example, via a current, depending on the state of charge of the energy storage device. The drive control unit can be configured so that, for a recuperation process, a braking process, or a coasting process, the energy storage device is charged by at least one of the recuperation energy and the fuel cell energy.

[0037] A fourth aspect describes a working machine. Further features, effects, and advantages for the fourth aspect can be derived from one of the preceding aspects. Furthermore, features, effects, and advantages of the fourth aspect also represent features, effects, and advantages for one of the preceding aspects. The working machine has a drive device according to one of the embodiments of the first aspect and / or a control device according to the third aspect. The working machine can have at least one traction element. The traction element can comprise at least one drive wheel, a drive axle, a driven axle unit, and a track drive. For example, the working machine can have two drive wheels. The at least one traction element can be configured via the drive device to propel the working machine.Regarding the design and advantages of the individual features, reference is made to the above explanations in connection with the first, second and third aspects. Brief description of the characters Fig. Figure 1 shows a flowchart of an embodiment of a drive device for a working machine. Fig. Figure 2 shows a flowchart of an embodiment of the drive device. Fig. 1. Fig. Figure 3 shows a schematic representation of a detail of an embodiment of the drive device. Fig. 1 and Fig. 2. Fig. Figure 4 shows a diagram of an embodiment of an energy storage device of the drive unit. Fig. 1, Fig. 2 to Fig. 3. Fig. Figure 5 shows a diagram of an embodiment of a fuel cell device of the drive unit. Fig. 1, Fig. 2, Fig. 3 to Fig. 4. Fig. Figure 6 shows a schematic representation of an embodiment of a control device for the drive device. Fig. 1, Fig. 2, Fig. 3, Fig. 4 to Fig. 5. Fig. Figure 7 shows a flowchart of an embodiment of a method for controlling the drive device. Fig. 1, Fig. 2, Fig. 3, Fig. 4 to Fig. 5. Fig. Figure 8 shows a schematic representation of an embodiment of a working machine with a drive device according to Fig. 1, Fig. 2, Fig. 3, Fig. 4 to Fig. 5. Fig. Figure 9 shows a flowchart of a procedure for controlling a drive device. Detailed description of embodiments

[0038] Fig. Figure 1 shows a flowchart of an embodiment of a drive device for a working machine, in this case a wheel loader. The drive device has a Fig. 1 traction motor 21 (not shown), a working device 36, a working pump 32, a fluid storage device 12 and a [unclear] Fig. 1 fuel cell device 13 (not shown). The drive device is designed for hydraulic recuperation, for operating the fuel cell device 13 to provide fuel cell energy, and for outputting the load point reduction energy of the fluid storage device 12 to support the fuel cell device 13.

[0039] The traction motor 21 is designed to propel the working machine and to generate recuperation energy when the working machine decelerates, and is configured as an electric motor in this case. The fuel cell unit 13 is designed to generate electrical energy to operate the traction motor 21. Furthermore, the fuel cell unit 13 is designed to generate the energy required to operate the fuel cell unit 13 within its optimal operating range during a recuperation, braking, or coasting process. The working unit 36 ​​is designed to perform a work task, in this case, the hydraulic lifting and lowering of a load, on the working machine.

[0040] The working pump 32 is designed to supply a pressurized fluid, in this case hydraulic oil, at a pressure level suitable for the working device 36. The working device 36 can be operated via the fluid output of the working pump 32. For this purpose, the working pump 32 is fluidically connected to the working device 36 via a first valve 51. Furthermore, the working pump 32 is fluidically connected via the first valve 51 to system elements 37, in this case switching elements and transmission elements, for actuating, lubricating, and cooling the system elements 37. The working pump 32 can be operated by a working motor 31, in this case an electric motor. The working motor 31 can be driven by the recuperated energy of the traction motor 21 and by the fuel cell energy of the fuel cell unit 13.

[0041] The fluid storage device 12 is designed to store the pressurized fluid of the working pump 32 with a variable, pressurized volume. In this case, the pressure is generated via a pneumatic pre-tensioning element. The fluid storage device 12 is fluidically connected to the working pump 32 via a second valve 52 for receiving the pressurized fluid. To discharge the pressurized fluid, the fluid storage device 12 is fluidically connected via the second valve 52 to the first valve 51, and thus to the working device 36 and the system elements 37, in order to operate them. The fluid storage device is thus configured to deliver the load point reduction energy for operating the working device 36 and the system elements 27 via the fluid storage device. The fluid is directed from the working device 36 and the system elements 37 to an intermediate fluid storage tank designed as an oil sump.The fluid storage unit supplies the working pump 32 with fluid. The working unit 36 ​​and the system elements 37 can be operated via the pressurized fluid stored in the fluid storage unit 12. This allows electrical recuperation energy and fuel cell energy to be effectively stored via fluid energy in the fluid storage unit 12 and used as needed to operate at least one of the working unit 36 ​​and the system elements 37.

[0042] The fuel cell device can be operated in the nominal operating range via the working pump 32 and the fluid storage device 12, even if the energy requirement of the drive device differs from the nominal energy of the fuel cell device 13.

[0043] Fig. Figure 2 shows a flowchart of an embodiment of the drive device. Fig. 1. In the present embodiment, the drive device additionally includes an energy storage device 11, in this case a battery. The present embodiment is controllable via a control unit comprising a vehicle control unit 61, a hydraulic control unit 62, and a drive control unit 63. Furthermore, the drive device of the present embodiment includes an inverter 64 for operating the working motor 31.

[0044] The vehicle control unit 61 controls the energy flow between the energy storage device 11, the fuel cell device 13, and the working motor 31. For a recuperation process of the working machine, the vehicle control unit 61 sets a maximum charging current for a maximum charging power of the energy storage device 11, which depends on the state of charge of the energy storage device 11. The value for the maximum charging current is then transmitted to the drive control unit 63. The vehicle control unit 61 sets a maximum storage power for storing fluid energy in the fluid storage device 12, depending on the state of charge of the fluid storage device 12. The vehicle control unit 61 sets a load point increase power depending on an optimal operating range of the fuel cell device 13.The vehicle control unit 61 now sets a recuperation power depending on the maximum charging power, the maximum storage power, and the load point increase power. To convert the recuperation energy and the load point increase power into fluid energy, the drive control unit 63 increases the electrical power to drive the working motor 31 via the inverter 64. This drives the working pump 32 and generates pressurized fluid.

[0045] The vehicle control unit 61 transmits a control signal to the hydraulic control unit 62 to control the first valve 51 and the second valve 52. The pressurized fluid is directed via the first valve 51 and the second valve 52 either to storage in the fluid storage device 12 or to operate the working device 36 and / or the system elements 37. In one embodiment, a single multi-way valve is provided instead of the first valve 51 and the second valve 52.

[0046] Fig. Figure 3 shows a schematic representation of a detail of an embodiment of the drive device. Fig. 1 and Fig. 2. In the present case, the drive device additionally comprises a traction gearbox 25, a working gearbox 35, and a system pump 33. The working pump 32 and the system pump 33 have a common drive shaft for being driven by the working motor 31. The drive shaft of the working motor 31 is mechanically connected to the common drive shaft of the working pump 32 and the system pump 33 via the working gearbox 35. The system pump 33 is used for actuating, lubricating, and cooling the components in the working gearbox 35. Fig. 3 system elements not shown 37 were set up.

[0047] The traction transmission 25 comprises an input element, an output element, a first traction switching element 26, and a second traction switching element 27. The input element of the traction transmission 25 is mechanically connected to the output element of the traction transmission 25 via a first three-stage spur gear unit and a second three-stage spur gear unit. The traction transmission 25 provides two different gear ratios between the input element and the output element. These different gear ratios can be selected via the first traction switching element 26 and the second traction switching element 27. The drive shaft of the traction motor 21 is rotationally fixed to the input element of the traction transmission 25. Different spur gear pairings between the input element and the output element can be selected via the first traction switching element 26 and the second traction switching element 27.The output element of the traction transmission 25 is non-rotatably connected to a traction element 28, in this case a drive shaft of the working machine.

[0048] Fig. Figure 4 shows a diagram of an embodiment of the energy storage device 11 of the drive device. Fig. 1, Fig. 2 to Fig. 3. The diagram shows the discharge power X1 and charging power X2 of the energy storage device 11 as a function of the energy storage device's state of charge. The discharge power drives at least one of the traction motors 21 and the working motor 31. The charging power stores the recuperated energy of the traction motor 21 in the energy storage device 11. The charging power X2 is limited within a range A when the state of charge is higher than approximately 75% and lower than approximately 90%. The charging power X2 approaches zero when the state of charge is higher than approximately 90%. The discharge power X1 is limited when the state of charge is lower than approximately 5%.

[0049] Fig. Figure 5 shows a diagram of an embodiment of a fuel cell device 13 of the drive device. Fig. 1, Fig. 2, Fig. 3 to Fig. 4. The diagram shows the cell voltage X3, system efficiency X4, and power density X5 of the fuel cell unit 13 as a function of the current density of the fuel cell unit 13. The system efficiency X4 is particularly high in region C and represents an optimal operating range for the fuel cell. If the fuel cell is throttled to a lower current density, as in region B, the system efficiency X4 decreases significantly. If the fuel cell unit 13 is operated at a higher current density than in region C, as in region D, for example, the system efficiency X4 also decreases. The drive system is designed so that the fuel cell unit 13 can be operated in its optimal operating range, for example, also during recuperation, braking, and coasting.

[0050] Fig. Figure 6 shows a schematic representation of an embodiment of a control device for the drive device. Fig. 1, Fig. 2, Fig. 3, Fig. 4 to Fig. 5. The control unit comprises the vehicle control unit 61, the hydraulic control unit 62, and the drive control unit 63. The vehicle control unit 61 communicates with the hydraulic control unit 62 and the drive control unit 63. The control unit is configured to perform the following functions with reference to Fig. to carry out the 7 described procedures.

[0051] Fig. Figure 7 shows a flowchart of an embodiment of a method for controlling the drive device. Fig. 1, Fig. 2, Fig. 3, Fig. 4 to Fig. 5. In a first step, the method comprises providing I the fuel cell energy via the fuel cell unit 13. In a further step, the method comprises recuperating V energy via the traction motor 21. In a further step, the method comprises operating II the working pump 32 using the fuel cell energy and the recuperated energy to provide pressurized fluid at a pressure level for the working unit 36 ​​using the fuel cell energy to increase the operating power of the fuel cell unit 13. In a further step, the method comprises storing III the pressurized fluid of the working pump 32 in the fluid storage unit 12.In a further step, the procedure includes operating the working device 36 with load point reduction energy output by the fluid storage device 12 to reduce the operating power of the fuel cell device 13.

[0052] In a further embodiment, the provision of fuel cell energy (I) is carried out when the requested power for the drive device is less than the nominal power of the fuel cell unit 13, or when a requested power reduction for the drive device exceeds the power variability of the fuel cell unit 13. In a further embodiment, the operation of the working device (IV) (IV) with the load point reduction energy is carried out at least when the requested power for the drive device is greater than the nominal power of the fuel cell unit 13, or when a requested power increase for the drive device exceeds the power variability of the fuel cell unit 13.

[0053] Fig. Figure 8 shows a schematic representation of an embodiment of a working machine with a drive device according to Fig. 1, Fig. 2, Fig. 3 to Fig. 4, which is set up to conduct a procedure according to Fig. 6. The working machine has the working motor 31. The arrow leading away from the working motor 31 shows a power flow from the working motor 31 to the working pump 32 and to the system pump 33. The traction motor 21 can drive either the rear axle or the front axle of the working machine. The arrows leading away from the traction motor 21 show a power flow from the traction motor 21 to the front axle and the rear axle during traction operation of the working machine. In recuperation mode of the working machine, the power flow is in the opposite direction to the arrows. The front axle and the rear axle each have two traction elements 28 designed as drive wheels, which are connected to the front axle and the rear axle, respectively, at opposite ends of the working machine.

[0054] Fig. Figure 9 shows a flowchart of a method for controlling a drive device without a fluid storage device. During a drive operation, the requested power P comm greater than zero.

[0055] If the requested service P comm greater than the rated power P fc-rated If the fuel cell device 13 is in operation, a hybrid drive takes place in which additional drive power is provided by the energy storage device 11, provided that the energy in the energy storage device 11 does not thereby fall below a minimum energy E min would fall. Otherwise, the fuel cell unit 13 will be used in an excessively high operating mode to increase the fuel cell power P. fc the fuel cell unit 13 to the requested power P comm to increase.

[0056] If the requested service P comm the rated power P fc-ratedIf the fuel cell unit 13 corresponds to this, then propulsion is exclusively via fuel cell unit 13. This corresponds to operating range C of the Fig. 5.

[0057] If the energy in the energy storage device 11 remains smaller than a maximum energy E max , the energy storage device 11 is additionally charged. However, if the energy in the energy storage device 11 is greater than a maximum energy E max , so the fuel cell unit 13 is throttled to zero and the requested power P comm is provided by energy storage unit 11. This corresponds to operating area B of the Fig. 5.

[0058] During braking as well as during coasting, the required power P comm less than zero.

[0059] If the energy in the energy storage device 11 is greater than or equal to a maximum energy E through recuperation max If this occurs, the fuel cell unit 13 is throttled to zero, and no further energy is drawn from the energy storage unit 11. The power generated by recuperation is then fed exclusively to a braking resistor and converted into heat.

[0060] However, if the energy in the energy storage device 11 is not greater than or equal to a maximum energy E through recuperation max If this were to happen, the fuel cell unit 13 would again be throttled back to zero. The recuperated energy is fed to the energy storage unit 11. This corresponds to operating range B of the Fig. 5. Reference sign 11 Energy storage device 12 Fluid storage device 13 Fuel cell equipment 21 Traction engine 25 traction gearboxes 26 First traction switching element 27 Second traction switching element 28 traction elements 31 Working engine 32 Working pump 33 System pump 35 working gears 36 Work setup 37 System element 51 First valve 52 Second valve 61 Vehicle control unit 62 Hydraulic control unit 63 Drive control unit 64 Inverter A Operating area of ​​the energy storage facility B Operating area of ​​the fuel cell facility C Operating area of ​​the fuel cell system X1 discharge power X2 charging power X3 cell voltage X4 System efficiency X5 power density I Providing fuel cell energy II Operating the working pump III. Storing the pressurized fluid IV. Operation of the work facility V Energy recuperation by the traction motor P brake_chopper power wasted via braking resistance P comm Requested service P fc-rated Rated power of the fuel cell P fc Power provided by the fuel cell P pps_traction Power provided by the energy storage system P pps_charging Power supplied to the energy storage system Available energy in the energy storage system E min Minimum amount of energy that should remain in the energy storage system E max maximum amount of energy to be stored in the energy storage system

Claims

[1] Drive device for a working machine comprising a fuel cell unit (13) for operating the drive device and for providing excess fuel cell energy, a working unit (36) for performing a work task of the working machine, a working pump (32) for providing a pressurized fluid at least at a pressure level for the working unit (36), wherein the working pump (32) can be operated by the fuel cell energy of the fuel cell unit (13), and a fluid storage unit (12) for storing the pressurized fluid of the working pump (32) and for releasing the pressurized fluid at the pressure level for the working unit (36) as a load point reduction energy, wherein the working unit (36) can be operated at least via the pressurized fluid of the fluid storage unit (12),The operating power of the fuel cell device (13) can be increased by operating the working pump (32) with the excess fuel cell energy of the fuel cell device (13), and the operating power of the fuel cell device (13) can be reduced by outputting the load point reduction energy to operate the working device (36) via the fluid storage device (12). [2] Drive device according to claim 1, characterized by , that the drive device has a traction motor (21) for moving the working machine and the fuel cell device (13) is set up to operate the traction motor (21). [3] Drive device according to claim 2, characterized by , that the traction motor (21) is designed to generate recuperation energy and the working pump (32) can be operated by the recuperation energy of the traction motor (21). [4] Drive device according to one of the preceding claims, characterized by that the drive device has a working motor (31) for driving the working pump (32). [5] Drive device according to claim 4, characterized by , that the drive device has an energy storage device (11) for storing at least the fuel cell energy and for providing electrical load point reduction energy for operating the working motor (31). [6] Drive device according to one of the preceding claims, characterized by , that the working pump (32) is fluidically connected to the fluid storage device (12), and the fluid storage device (12) is fluidically connected to the working device (36) via a first valve (51). [7] Drive device according to claim 6, characterized by, that the working pump (32) is fluidically connected to the fluid storage device (12) via a second valve (52), and the fluid storage device (12) is fluidically connected to the first valve (51) via the second valve (52). [8] Drive device according to any one of claims 4 to 7, characterized by , that the drive device has a system pump (33) for providing a pressurized fluid at least at a pressure level for system elements (37) of the drive device, the working motor (31) is designed to drive the system pump (33) and the working pump (32), and the working pump (32) and the system pump (33) have a common drive shaft for being driven by the working motor (31). [9] Method for operating a drive device according to one of the preceding claims, comprising providing (I) fuel cell energy via the fuel cell device (13), operating (II) the working pump (32) to provide pressurized fluid at least at a pressure level for the working device (36) by means of the fuel cell energy to increase the operating power of the fuel cell device (13), storing (III) the pressurized fluid of the working pump (32) in the fluid storage device (12), and operating (IV) the working device (36) with load point reduction energy supplied by the fluid storage device (12) to reduce the operating power of the fuel cell device (13). [10] Method according to claim 9, characterized by, that the provision (I) of fuel cell energy is carried out at least when a requested power for the drive device is less than a rated power of the fuel cell device (13) or when a requested power reduction for the drive device exceeds a power change capability of the fuel cell device (13). [11] Method according to claim 9 or 10, characterized by , that the procedure for operating (IV) the working device (36) with the load point reduction energy is carried out at least when the requested power for the drive device is greater than a rated power of the fuel cell device (13) or when a requested power increase for the drive device exceeds a power change capability of the fuel cell device (13). [12] Control device configured to perform a method according to any one of claims 9 to 11. [13] Working machine with a drive device according to one of claims 1 to 8 and / or a control device according to claim 12.

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