Drive system and method for operating a drive system

Abstract

Drive system (100) of a working machine (200) comprising at least one electric motor (50, 60), a transmission device (10), and a control device (110), which is configured to select a gear ratio of the transmission device (10) depending on a driving requirement (122) and taking into account a respective characteristic map (51, 61) of the at least one electric motor (50, 60), characterized in that the control device (110) is configured to select the gear ratio of the transmission device (10) taking into account a power flow distribution formed via the transmission device (10) in the drive system (100).

Description

[0001] The present invention relates to a drive system for a work machine. The invention also relates to a work machine with such a drive system. Furthermore, the invention relates to a method for operating a drive system for a work machine and a control device for carrying out such a method.

[0002] Conventional drive trains for working machines can consist of an internal combustion engine and a mechanically coupled transmission with multiple gears. The internal combustion engine can be operated at different operating points depending on the required power output, with the operating point being selected taking fuel efficiency considerations into account. Electrically driven working machines are also known.

[0003] From DE 10 2005 037 032 A1, a transmission control system for a working machine is known, which has a transmission and a traction device with a braking mechanism. The transmission control system has a speed sensor configured to generate a signal indicating the working machine's travel speed. The transmission control system also has a control device connected to the speed sensor and the braking mechanism. The control device is configured to determine when a gear change of the transmission is desired and to adjust the operation of the braking mechanism in response to the signal from the speed sensor when a gear change of the transmission is desired.

[0004] DE 10 2005 023 672 A1 discloses a method for controlling an electrically driven work machine comprising a motor and an electric motor that provides power to enable the work machine to travel across a terrain surface at certain speeds. The method includes detecting a reverse direction change of the work machine, which causes the work machine to operate in a reverse drive cycle. Furthermore, the method includes executing a motor speed reduction process that reduces the current motor speed based on the detected reverse direction change, without reducing the travel speed of the work machine during the reverse drive cycle.

[0005] The invention relates in one aspect to a drive system for a work machine. The drive system can be designed as an electric drive system for an electrically powered work machine. The drive system is designed to move the work machine. The drive system of the work machine can power a chassis with which the work machine can be moved. The work machine can be a self-propelled work machine (SPW). Therefore, the work machine can be a mobile work machine. The work machine can be designed as a battery-powered work machine, or a so-called BEV work machine. The work machine can be designed as a vehicle that is designed to perform at least one work task that is not intended for transporting persons and / or goods.The machine can have a working device or tool for this purpose. To power the working device, the machine can have a drive system. The machine can be a construction machine and / or an agricultural machine. For example, a wheel loader, a tractor, a concrete mixer, a garbage truck, or a refrigerated truck. The machine can be an automated machine that can be remotely controlled. The automated machine can be designed as an autonomous machine.

[0006] The drive system comprises at least one electric motor and a transmission unit. The drive system of the working machine can be powered via the transmission unit and the at least one electric motor. Furthermore, the working drive of the working machine can be driven via a clutch by the at least one electric motor. The at least one electric motor can be supplied with energy from a power source. This power source can be a battery and / or a fuel cell, which may be located on the working machine. The electric motor can be designed as an asynchronous machine, a synchronous machine, and / or a reluctance machine. In other words, the at least one electric motor can be any known electric motor design suitable for driving the drive system of a working machine.

[0007] The machine can further comprise two electric motors, which can be supplied with energy from one or two energy sources. The machine's travel drive can be powered via the transmission unit by at least one of the two electric motors. The machine's working drive can also be powered via the transmission unit by at least the other of the two electric motors. If the travel drive and / or the working drive is powered by both electric motors, the second electric motor can provide supplementary drive power to the first electric motor. The transmission unit can thus be connected on the input side to two electric motors and on the output side to two independent machine drives, for example, a travel drive and a working drive.The gearbox can therefore be designed, for example, to translate two input motor speeds from two electric motors into two output speeds for two machine drives.

[0008] The drive system also includes a control unit configured to select the gear ratio of the transmission unit based on a driving requirement and taking into account the respective characteristic map of the at least one electric motor. A control unit's configuration for performing a step refers to the specific preparation, such as programming, of the control unit to execute that step. The driving requirement and the respective characteristic map can thus represent input variables for the control unit, which it can read via at least one interface. The control unit can also have an interface for outputting a control command to the transmission unit. The control command can specify a selected gear ratio that can be provided by the transmission unit.The control unit can also be configured solely to adjust the gear ratio of the transmission. The control unit can function as a driving strategy controller or a driving strategy regulator.

[0009] The driving request can depend on the driving situation of the machine. It can arise from a predefined and automated movement of the machine and / or be specified by the machine's control system. The driving request can include a power requirement for the machine's drive system. This power requirement can specify a target speed and / or torque, for example, at a specific location within the drive system. The target speed and / or torque of the drive system can correspond to an output speed / torque provided by the transmission. The driving request can be initiated by the operator of the machine, for example, by actuating a control element. If the driving request is initiated by an operator, it can involve the position of an accelerator or brake pedal.Alternatively or additionally, the driving request can be specified by a control device, which may be located on the working machine and / or separately from the working machine.

[0010] The at least one characteristic map of the at least one electric motor can include at least one efficiency characteristic map. The efficiency of the at least one electric motor can be defined by the characteristic map as a function of at least one motor speed and at least one motor torque. The gear ratio of the transmission can thus be selected by the control unit to meet the driving requirements such that the at least one electric motor operates at a specific operating point with optimized efficiency. The operating point of the at least one electric motor can, for example, lie within a partial load range of its characteristic map.

[0011] If the machine has two electric motors, the control unit can be configured to select the gear ratio based on the driving requirements and taking into account the individual characteristic curves of the two electric motors. Based on these two characteristic curves, a combined or superimposed characteristic curve for the two electric motors can be used. This combined characteristic curve can include a combined efficiency curve for the two electric motors. The combined overall efficiency of the two electric motors can be defined by this combined characteristic curve, taking into account the respective motor speeds and torques. The gear ratio can thus be selected by the control unit to meet the driving requirements, ensuring that both electric motors operate with optimized overall efficiency at each operating point.The two electric motors do not necessarily have to be operated with a motor-specific optimized efficiency. Therefore, the overall efficiency of at least two electric motors on a machine can be advantageously optimized by selecting the appropriate gear ratio.

[0012] The drive system of the present invention enables the movement of an electrified work machine in an energy-efficient manner. More precisely, the drive system of the present invention allows a driving requirement to be implemented efficiently. The drive of the work machine can thus be operated in a performance-optimized manner, whereby the power available from an energy source can be used efficiently to move the work machine.

[0013] According to one embodiment of the drive system, the drive system's transmission unit comprises at least two transmission units. Selecting the transmission ratio can involve choosing between two selectable ratios from these at least two transmission units. The at least two transmission units can be configured to convert at least two input speeds from at least two electric motors to at least two output speeds for at least two machine drives. One transmission unit can be provided to convert the motor speed of one electric motor to a speed suitable for the drive system. Another transmission unit can be provided to convert the motor speed of another electric motor to a speed suitable for the working drive. The at least two transmission units can be connected to each other via a mechanical linkage.The mechanical connection can enable a mechanical power flow within the transmission system between the at least two transmission units. An advantage of this power flow between the at least two transmission units is that, in addition to the drive power from one electric motor, the drive system can be supplemented with further drive power from another electric motor. The control unit can be configured to select the respective gear ratio of the at least two transmission units in such a way as to optimize the overall efficiency of the drive system.

[0014] According to a further embodiment of the drive system, the control unit is configured to select the gear ratio of the transmission unit taking into account a load condition of at least one of the drive units and one working drive. The load condition can be the current actual load condition of at least one of the aforementioned drives. The load condition can include a currently applied torque and / or a currently applied rotational speed, which can be determined, for example, by a sensor. The load condition can include a target torque in the drive unit required to move the machine. Alternatively or additionally, the load condition can include a torque in the working drive required to actuate the working unit. The working unit of the machine can include working hydraulics, and the load condition can include a load condition of the working hydraulics of the working unit.Consequently, current load conditions on at least one drive of the working machine can be taken into account when controlling the gearbox with the control unit.

[0015] According to a further embodiment of the drive system, the control unit is configured to select the gear ratio of the transmission unit taking into account the operating state of a work unit connected to a working drive. This operating state can be that of the working hydraulics or of a working tool of the work unit. The operating state can include the position, movement, and / or fill level of the working tool. The working tool can be, for example, a lifting frame and / or a bucket. Thus, the transmission unit can be controlled, taking into account the current working situation, in such a way that the at least one electric motor can be operated at an optimized operating point even during the current working situation.If the machine being worked is a wheel loader, the operating condition of the lifting frame and / or the bucket can be taken into account, for example, during a rise run of the wheel loader, in which the wheel loader starts moving and simultaneously raises the bucket.

[0016] According to one embodiment of the drive system according to the invention, the control unit is configured to select the gear ratio of the transmission unit taking into account a power flow distribution formed across the transmission unit in the drive system. The driven machine can have a power flow control, for example, a power controller. The current power flow from an energy source to the at least one electric motor, the current power flow from the at least one electric motor to the transmission unit, for example, to individual gear units of the transmission unit, and / or the current power flow via the transmission unit to the drive system and / or to the working drive can thus be taken into account when controlling the transmission unit by the control unit.The maximum power output that the at least one electric motor can provide at any given time can therefore be taken into account when selecting the gear ratio of the transmission. Advantageously, this allows a power flow to be reserved for a specific component, independent of the electric motor's optimal operating point. For example, a power reserve for the working equipment can thus be continuously maintained via the transmission, regardless of the machine's optimized driving operation.

[0017] In a further embodiment of the drive system, the control unit is configured to select the gear ratio of the transmission taking into account a cumulative load state of the transmission. The cumulative load state can include at least one cumulative load state for at least one gear ratio range, for example, for at least one gear stage of the transmission. A cumulative load on the transmission can thus be advantageously distributed over the selectable gear ratio range. In other words, when selecting the gear ratio of the transmission, a cumulative load of a gear ratio range can be considered in order to avoid overloading in that gear ratio range. The control unit can therefore also advantageously perform active condition monitoring.This allows for the optimization of the service life of the transmission unit in addition to the efficiency of the drive system.

[0018] In another embodiment of the drive system, the control unit is configured to select the transmission ratio based on the temperature condition within the drive system. This temperature condition can be the current temperature of the at least one electric motor and / or the current temperature within the transmission unit, for example, in one or all of the transmission units. This allows the drive system to perform thermal management in addition to efficient operation. For example, by changing the transmission ratio, the electric motor can be operated in a continuous operating mode (S1 mode) on the so-called S1 curve of the electric motor. For this purpose, the transmission unit can be operated in its lowest gear, for example, a crawler gear.Operating the electric motor in the so-called S2 mode, which is associated with higher heat generation, can be avoided by adjusting the gearbox accordingly.

[0019] The invention relates in a further aspect to a working machine with a drive system according to one of the previously described embodiments. The invention further relates to a method for operating a drive system for a working machine comprising at least one electric motor and a transmission unit. In one step of the method, a driving request is read in. This reading can involve transmitting the driving request to a control unit or querying the driving request by the control unit. In a further step of the method, a gear ratio of the transmission unit is selected depending on the read driving request and taking into account a respective characteristic map of the at least one electric motor.A control unit is used to select the gear ratio of the transmission system, taking into account the power flow distribution formed via the transmission system in the drive system.

[0020] The invention relates in a further aspect to a control device configured to carry out the steps of the method according to the preceding aspect. This control device may be the same control device described in the first aspect. For an understanding of the individual features and their advantages, reference is made to the above explanations. Fig. Figure 1 schematically shows a drive system with further components of a working machine according to an embodiment of the invention. Fig. Figure 2 schematically shows a working machine with a drive system and a control device according to a respective embodiment of the invention. Fig. Figure 3 shows a flowchart with steps of a method for operating a drive system for a working machine according to an embodiment of the invention.

[0021] Fig. Figure 1 schematically shows a drive system 100 from a in Fig. 2 shown work machine 200. The in Fig. The drive system 100 shown in Figure 1 comprises two electric motors 50 and 60 and a power source 70. The power source 70 supplies energy to the first electric motor 50 and the second electric motor 60 and is electrically connected to both electric motors 50 and 60 for this purpose. A first characteristic map 51 for the first electric motor 50 is stored in a storage unit 140 of the drive system 100. A second characteristic map 61 for the second electric motor 60 is stored in the storage unit 140 of the drive system 100. In an alternative embodiment of the drive system 100, it comprises only one of the electric motors 50 and 60, with only the characteristic map 51 or 61 of that single electric motor 50 or 60 being stored in the storage unit 140.

[0022] The drive system 100 also includes a transmission unit 10. The transmission unit 10 comprises two transmission units 30 and 40. The first transmission unit 30 is mechanically connected to the first electric motor 50 via a first transmission input 12 of the transmission 10. The second transmission unit 40 is mechanically connected to the second electric motor 60 via a second transmission input 22. The two transmission units 30 and 40 are also connected to each other via a mechanical linkage 32. In an alternative embodiment of the drive system 100, it has only one of the two transmission units 30 or 40, which is mechanically connected to only one of the electric motors 50 or 60 via at least one of the two transmission inputs 12 or 22, respectively.

[0023] The transmission unit 10 of the drive system 100 is connected via a first transmission output 14 to a drive unit 80 of the in Fig. The working machine 200 shown in Figure 2 is mechanically connected. The drive 80 is mechanically connected to a chassis 82 for driving the same. In one embodiment, the chassis 82 has the [features / components] shown in Figure 2. Fig. 2 wheels 83 shown, which are connected to the drive mechanism 80 via the chassis 82 for moving the in Fig. The working machine 200 shown in section 2 is driven by the transmission unit 10 of the drive system 100. The transmission unit 10 is also connected via a second transmission output 24 to a working drive 90 of the [unclear text]. Fig. The working machine 200 shown in Figure 2 is mechanically connected. The working drive 90 is connected to a working device 92 for driving the same. In embodiments not shown, the working device 92 comprises a rotaryally driven drum of a concrete mixer or a hydraulically actuated press of a refuse truck.

[0024] The transmission unit 10 of the drive system 100 is configured to translate a first motor speed 52 of the first electric motor 50 via the first transmission unit 30 into a first drive speed 54 of the drive 80. The transmission unit 10 is also configured to translate a second motor speed 62 of the second electric motor 60 via the second transmission unit 40 into a second drive speed 64 of the working drive 90.

[0025] The drive system 100 also includes a control unit 110 for controlling the transmission unit 10. For this purpose, the control unit 110 is communicatively connected to the two transmission units 30 and 40 via respective control interfaces 11 and 111 of the transmission unit 10 and the control unit 110. The control unit 110 controls the two transmission units 30 and 40 in order to set a respective gear ratio in them and thus a gear ratio of the transmission unit 10.

[0026] Furthermore, a driving request 122 is communicated to the control unit 110 via a request interface 112 from a driving request transmitter 120. In one embodiment, the driving request 122 is a movement instruction for the working machine 200. Taking into account the two characteristic maps 51, 61 of the two electric motors 50, 60 stored in the memory unit 140, the control unit 110 determines a gear ratio for each of the transmission units 30, 40 and transmits this to the transmission unit 10. For this purpose, the characteristic maps 51, 61 are communicated to the control unit 110 via a respective characteristic map interface 114, 144 of the memory unit 140 and the control unit 110.

[0027] Fig. Figure 2 shows a work machine 200 with the Fig. The drive system 100 described in Section 1. The working machine 200 has the drive 80 and the chassis 82, which has wheels 83. The working machine 200 also has the working drive 90 and the working device 92. The drive 80 is supplied with energy from the energy source 70 via the first electric motor 50 and the transmission device 10 in a first power flow 81. The working drive 90 is supplied with energy from the energy source 70 via the second electric motor 60 and the transmission device 10 in a second power flow 91. In one embodiment, the two energy flows 81, 91 form two independent power flows 81, 91. In another embodiment, the two power flows 81, 91 are connected in the transmission device 10 by a power flow connection (not shown) via the [unclear text]. Fig. The mechanical connection 32 shown in Figure 1 connects the two transmission units 30 and 40. The drive system 100 of the working machine 200 also assigns the following additional functions: Fig. 1 described system components.

[0028] In Fig. 3 are steps S1, S2 for executing a procedure for operating the in the Fig. 1 and Fig. 2 shown drive system 100 for the in Fig. Figure 2 shows the working machine 200 in a chronological sequence. In a first step S1, the driving request 122 is read by the control unit 110. In a subsequent second step S2, the control unit 110 determines a gear ratio of the transmission unit 10, as shown in Figure 2. Fig. As described in section 1, a specific gear ratio is selected for the transmission units 30 and 40 of the transmission device 10. The gear ratio of the transmission device 10 is selected based on the driving request 122 received by the control unit 110. The gear ratio of the transmission device 10 is also selected taking into account at least one read-in characteristic map 51 or 61 of the electric motors 50 and 60.

[0029] In Fig. Figure 2 also shows a control unit 130 which communicates with the drive request transmitter 120 and the storage unit 140 in order to control the transmission unit 10 according to steps S1, S2 and thus carry out the described procedure. Reference sign 10 Gearbox unit 11, 111 Control interface 12, 22 Gearbox input 14, 24 Gearbox output 30, 40 Gear unit 32 mechanical connection 50, 60 electric motor 51, 61 map 52, 62 engine speed 54, 64 Drive speed 70 Energy source 80 drive 81, 91 Power flow 82 Chassis 90 working drive 92 Work equipment 100 Drive system 110, 130 Control unit 112 Requirements interface 114, 144 map interface 120 drive request transmitters 122 Driving request 140 storage units 200 working machine S1 Driving Request S2 Translation Choice

Claims

[1] Drive system (100) of a working machine (200) comprising at least one electric motor (50, 60), a transmission device (10), and a control device (110) which is configured to select a gear ratio of the transmission device (10) depending on a driving requirement (122) and taking into account a respective characteristic map (51, 61) of the at least one electric motor (50, 60), characterized by , that the control device (110) is configured to select the ratio of the transmission device (10) taking into account a power flow distribution formed via the transmission device (10) in the drive system (100). [2] Drive system (100) according to claim 1, characterized by, that the transmission device (10) has at least two transmission units (30, 40) connected to each other via a mechanical operative connection (32), wherein the control device (110) is configured to select a respective transmission ratio of the at least two transmission units (30, 40). [3] Drive system (100) according to claim 1 or 2, characterized by , that the control device (110) is set up to select the ratio of the transmission device (10) taking into account a load condition of at least one of a travel drive (80) and a working drive (90). [4] Drive system (100) according to any one of the preceding claims, characterized by , that the control device (110) is configured to select the translation of the transmission device (10) taking into account an operating condition of a working device (92) operatively connected with a working drive (90). [5] Drive system (100) according to any one of the preceding claims, characterized by , that the control device (110) is configured to select the ratio of the transmission device (10) taking into account a cumulative load condition of the transmission device (10). [6] Drive system (100) according to any one of the preceding claims, characterized by , that the control device (110) is configured to select the ratio of the transmission device (10) taking into account a temperature condition in the drive system (100). [7] Working machine (200) with a drive system (100) according to one of the preceding claims. [8] Method for operating a drive system (100) of a working machine (200) which has at least one electric motor (50, 60) and a transmission device (10), comprising the steps: reading (S1) a driving request (122), and selecting (S2) a gear ratio of the transmission device (10) depending on the read-in driving request (122) and taking into account a respective characteristic map (51, 61) of the at least one electric motor (50, 60), characterized by , that the transmission ratio of the transmission device (10) is selected by means of a control device (110) taking into account a power flow distribution formed via the transmission device (10) in the drive system (100). [9] Control device (130) which is configured to perform the steps of the method according to claim 8.

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