Method for adaptively setting a shift point of a multi-speed powershift transmission of a working machine, control device, computer program product, working machine

Abstract

Method (100) for adaptively setting a shift point (P) of a multi-speed powershift transmission (4) of a working machine (1), wherein the working machine (1) comprises the multi-speed powershift transmission (4), an electric drive system (2) and a control device (6), wherein the electric drive system (2) comprises a battery (3) and an electric motor (5), wherein the multi-speed powershift transmission (4) is operatively connected to the electric drive system (2), wherein the control device (6) is signal-effectively connected to the electric drive system (2) and the multi-speed powershift transmission (4), characterized in that - a tractive force (Z) that must be present during shifting operations (S) of the multi-speed powershift transmission (4) is specified, whereby this tractive force (Z) is specified as the maximum tractive force (Z), - a state variable (G) of the electric drive system (2) is determined, wherein the state variable (G) is designed as the state of charge (SOC; SOC1; SOC2; SOC3) of the battery (3) of the electric drive system (2), - starting from the state variable (G) and the specified tractive force (Z), a travel speed (v) of the working machine (1) is determined at which the specified tractive force (Z) is essentially maintained during the switching process (S), - the switching point (P) is set at this determined driving speed (v). - the switching operation (S) is carried out at the switching point (P) when the working machine (1) has the determined driving speed (v).

Description

[0001] The present invention relates to a method for adaptively setting a shift point of a multi-speed powershift transmission of a work machine, a control device, a computer program product and a work machine.

[0002] A gear shift, particularly a downshift in a multi-speed powershift transmission of a work machine, requires additional power from the prime mover driving the work machine to compensate for the prime mover's rotor inertia. In battery-powered work machines, the prime mover is an electric motor. The drivetrains of these battery-powered work machines can comprise an electric motor and a mechanically connected transmission with at least two gear stages. Based on the driving requirement and the electric motor's characteristic map, an appropriate gear can be selected. Large overlaps between the gears are possible with regard to the speed and tractive force of the work machine.

[0003] EP 0339202 A2 discloses a drive device for machines and vehicles in which a special shifting behavior is achieved when shifting down to a lower gear.

[0004] DE 10 2020 001 600 A1 shows a method for operating a drive train of a motor vehicle, which has an energy storage device for storing electrical energy, at least one electric traction machine that can be supplied with the electrical energy stored in the energy storage device, and a transmission in which a gear change is carried out in the transmission, via which the motor vehicle can be electrically driven by means of the traction machine, wherein the gear change is carried out as a function of a current electrical voltage of the energy storage device.

[0005] DE 100 24 034 A1 discloses a system and method for controlling a vehicle drivetrain, including an internal combustion engine, an automatic transmission with a plurality of selectable gear ratios, and a control device. Determining a driver-requested wheel torque is based on the accelerator pedal position, and determining a vehicle speed limit for a gear ratio change is based on the driver-requested wheel torque.

[0006] DE 195 15 534 A1 relates to a control device for an automatic transmission and a control method for the automatic transmission, wherein the shifting can be carried out without a shift routine directory by calculating a shift point.

[0007] DE 199 40 703 C1 relates to a method for engine and transmission control in a motor vehicle with an internal combustion engine controlled by an engine control unit and a multi-step automatic transmission controlled by a transmission control unit.

[0008] DE 101 17 162 A1 discloses an electronic transmission unit for gearshift control in a motor vehicle, which is connected to an electronic motor unit for controlling an internal combustion engine. The transmission unit determines the engine torque associated with a specified tractive force request as well as the engine torque adjustable by the motor unit for the current gear. If the engine torque associated with the specified tractive force request cannot be adjusted for the current gear, the transmission unit performs a gearshift if an engine torque can be adjusted in the new gear that is closer to the engine torque associated with the specified tractive force request than the engine torque adjustable in the current gear.

[0009] WO 02 / 006 072 A1 shows a control unit for adjusting the gear ratio of a transmission arranged together with an engine in a drive train in order to provide braking assistance through the braking torque of the engine.

[0010] Based on the prior art, the present invention is based on the object of proposing an improved method for determining the shift points of a multi-speed powershift transmission.

[0011] Based on the aforementioned object, the present invention proposes a method for adaptively determining a shift point of a multi-speed powershift transmission of a work machine having the features of claim 1, a control device having the features of claim 3, a computer program product having the features of claim 4, and a work machine having the features of claim 5. Further advantageous embodiments and developments emerge from the subclaims.

[0012] In a method for adaptively setting a shift point of a multi-speed powershift transmission of a work machine, wherein the work machine has the multi-speed powershift transmission, an electric drive system, and a control device, wherein the electric drive system has a battery and an electric motor, wherein the multi-speed powershift transmission is operatively connected to the electric drive system, wherein the control device is signal-effectively connected to the electric drive system and the multi-speed powershift transmission, a tractive force that must be present during shifting operations of the multi-speed powershift transmission is predetermined. A state variable of the electric drive system is determined. Based on the state variable and the predetermined tractive force, a travel speed of the work machine is determined at which the predetermined tractive force is essentially maintained during the shifting operation.The shift point is set at this determined travel speed. The shifting process is carried out at the shift point when the work machine reaches the determined travel speed.

[0013] The work machine can be designed as a vehicle that is configured to perform at least one work task that is not intended for transporting people and / or goods. For this purpose, the work machine can have a work device or a work tool. The work machine can have a work drive to drive the work device. The work machine can be a construction machine and / or an agricultural machine. For example, the work machine can be a wheel loader, a tractor, a concrete mixer, a waste disposal vehicle, a forklift truck, a refrigerated vehicle, etc. The work machine can be a conventional work machine or an automated work machine that can be remotely controlled. The automated work machine can be designed as an autonomous work machine.

[0014] The work machine has the electric drive system, which in turn has the battery and the electric motor. The battery is connected to the electric motor in an energy-efficient manner. In this context, "energy-efficient connection" means that the battery can supply the electric motor with energy when the electric motor is operating as a motor, and that the battery can be supplied with energy by the electric motor when the electric motor is operating as a generator, e.g., in recuperation mode. The electric motor is preferably designed as a permanent magnet electric motor and serves to drive the work machine. The battery forms an electrical energy storage device.The electric drive system can also have more than one electric motor, for example a first electric motor that can provide a travel drive for the work machine and a second electric motor that can provide an auxiliary drive for operating the work device or the work tool.

[0015] The work machine also features a multi-speed powershift transmission. The multi-speed powershift transmission serves to transmit the speed provided by the electric motor. For this purpose, the multi-speed powershift transmission is operatively connected to the electric drive system. More precisely, the multi-speed powershift transmission is operatively connected to the electric motor. The work machine can have one or more driven axles. Each driven axle can be connected to the electric motor via the multi-speed powershift transmission and driven by it. The multi-speed powershift transmission, in particular, allows the speed ratio between the electric motor and the driven axle to be varied. Alternatively or in addition to driven axles, individual wheels can also be driven.

[0016] The work machine also has the control device. The control device is preferably embodied as an ECU. The control device is connected to the electric drive system and the multi-speed powershift transmission in a signal-effective manner. "Connected to the multi-speed powershift transmission" in this context means that the control device is connected to the multi-speed powershift transmission and to the electric drive system in such a way that data and signals can be exchanged. The control device is configured to select a gear ratio of the multi-speed powershift transmission depending on the shift point determined by the method according to the invention. In other words, the control device can control the multi-speed powershift transmission so that a gear is changed, i.e., an upshift or downshift can be performed.The control device is also configured to receive and evaluate sensor-determined data and signals from the electric drive system, i.e., from the battery and / or the electric motor. Furthermore, the control device has a memory unit on which data can be stored.

[0017] In a first step of the method, the tractive force that must be present during gear shifts of the multi-speed powershift transmission is specified. This specified tractive force is stored in the memory unit of the control device. The tractive force or performance can refer to the power of the electric motor that can be delivered in continuous operation of the electric motor. Peak performance can refer to the maximum tractive force available by the electric motor. In this first step, the maximum tractive force is specified as the tractive force that must be present during gear shifts of the multi-speed powershift transmission. Thus, the maximum tractive force should be available during each gear shift so that the user of the work machine does not notice any drop in tractive force during operation of the work machine. The tractive force is therefore kept constant during operation of the work machine, namely at the value of the maximum tractive force.

[0018] The state variable of the electric drive system is determined. This state variable is determined using suitable sensors and transmitted to the control unit. The respective sensors are thus connected to the control unit via a signal-effective connection, allowing data and signals to be exchanged. The control unit can evaluate the data and / or signals provided by the sensors. Alternatively, the evaluation is performed by the corresponding sensors.

[0019] The state variable of the electric drive system is designed as a state variable of the battery, namely the battery's state of charge. The battery's state of charge indicates the amount of energy stored in the battery that can be made available to the electric motor. The battery's state of charge has a direct influence on the electric motor's performance, as it determines the voltage available to the electric motor. The battery's state of charge changes during operation of the machine and thus during operation of the electric motor over its operating period.

[0020] Based on the state variable and the specified tractive force, the driving speed of the work machine is determined at which the specified tractive force is essentially maintained during the gear shift. "Essentially maintained" here means that the tractive force drops so minimally during the gear shift that it is imperceptible to the user of the work machine. Preferably, the tractive force is maintained exactly during the gear shift and does not drop at all.

[0021] The driving speed is determined by the control device. Using an algorithm, the control device calculates, for a given state variable and a specified tractive force, the speed at which the gearshift can take place, so that the specified tractive force is essentially maintained or even exactly maintained. The gearshift point is set by the control device at this determined driving speed. The gearshift is carried out at the gearshift point when the work machine has reached the determined driving speed. When the work machine reaches the determined driving speed as its current driving speed, the gearshift takes place. This allows a higher or lower gear to be shifted as required. The current driving speed is determined using suitable sensors, e.g. a speed sensor, which are connected to the control device via a signal.

[0022] For example, with a battery charge level of 100% and a specified maximum tractive force, a gear shift can occur at, say, 17 km / h. The shift point is therefore set to 17 km / h. However, if the battery charge level is only 10% and the maximum tractive force is specified, the shift point is shifted towards a lower speed, for example, to 10 km / h. Thus, the gear shift occurs at a driving speed of the work machine of 10 km / h. The maximum tractive force is essentially maintained. The numerical values ​​are purely examples and should not be understood as limiting.

[0023] The advantage of the method presented here is that the drop in tractive force is kept as low as possible or minimized. Despite the gearshift, the tractive force remains the same or virtually the same for the user of the work machine, and no performance losses are incurred. The disadvantages caused by a drop in tractive force, such as unstable driving behavior or insufficient power supply to the work equipment to perform the necessary work, can thus be avoided.

[0024] The control device for the work machine comprises means for executing the steps of the method already described in the previous description. The control device can be connected to the multi-speed powershift transmission and the electric drive system of the work machine in a signal-effective manner. Thus, when used in a work machine, the control device is connected to the multi-speed powershift transmission and the electric drive system of the work machine in a signal-effective manner. This has already been described in the previous description. In order to establish these connections, the control device has interfaces via which a signal-effective connection can be enabled.

[0025] In addition, the control device is designed such that, when used in a work machine, it can be connected to sensors for signal transmission, e.g., sensors for determining the current speed of the work machine. For this purpose, the control device has at least one additional interface.

[0026] Furthermore, the control device has a memory unit on which data can be stored. This has also been described in the previous description. The control device can use a computer program product to carry out the method.

[0027] Based on the determined driving speed, the control unit activates the multi-speed powershift transmission to initiate a gear change at precisely that driving speed. This has already been described in the previous description.

[0028] The computer program product comprises instructions which, when executed by the control device, cause the control device to execute the method already described in the previous description. The computer program product may comprise program code containing these instructions. The program code may be embodied, for example, on a data carrier or as a downloadable data stream.

[0029] The work machine has a multi-speed powershift transmission, an electric drive system, and a control device, which has already been described in the previous description. The control device is connected to the multi-speed powershift transmission and the electric drive system for signal transmission. This has also been described above. The work machine is preferably designed as a wheel loader or a front loader.

[0030] Various embodiments and details of the invention are described in more detail with reference to the figures explained below. They show, by way of example: Fig. 1 a schematic representation of a working machine according to an embodiment, Fig. 2 a schematic representation of a traction force-speed diagram of the multi-speed powershift transmission of the working machine from Fig. 1, Fig. 3 a schematic representation of a torque-speed diagram of the working machine from Fig. 1, Fig. 4 a schematic representation of a torque-speed diagram of the working machine from Fig. 1, Fig. 5 a schematic representation of the method for adaptively setting a shift point of the multi-speed powershift transmission of the working machine from Fig. 1.

[0031] Fig. 1 shows a schematic representation of a work machine 1 according to an exemplary embodiment. The work machine 1 is a wheel loader with a bucket as its working tool. The work machine 1 has an electric drive system 2. The electric drive system 2 has a battery 3 and an electric motor 5. The electric motor 5 and the battery 3 are connected to one another for energy efficiency. The work machine 1 also has a multi-speed powershift transmission 4. The multi-speed powershift transmission 4 is operatively connected to the electric drive system 2. The multi-speed powershift transmission 4 is operatively connected to the electric motor 5 of the electric drive system 2. The work machine is driven by the electric drive system 2 so that it can move along a path. This is indicated by the longitudinal arrow.

[0032] The work machine 1 also has the control device 6. The control device 6 is signal-effectively connected to the multi-speed powershift transmission 4 and can control it. The control device 6 is signal-effectively connected to the electric drive system 2, more precisely to the battery 3 of the electric drive system 2 and to the electric motor 5 of the electric drive system 2. The control device 6 can query a charge state of the battery 3. The control device 6 can also query a current speed of the work machine 1 from a speed sensor 7, to which it is signal-effectively connected. The method 100 runs on the control device 6, which is described in Fig. 5 is shown.

[0033] Fig. 2 shows a schematic representation of a traction force-speed diagram of the multi-speed powershift transmission of the working machine from Fig. 1. The speed of the driven machine is shown on the abscissa 31. The tractive force of the driven machine is shown on the ordinate 30. The curve of the tractive force versus speed is shown as an example in first gear 50 and second gear 51.

[0034] It is clearly evident that there is a larger overlap between the two gears 50 and 51. This makes it possible to select the shift point for changing between the two gears 50 and 51 adaptively.

[0035] Fig. 3 shows a schematic representation of a torque-speed diagram of the working machine from Fig. 1. The speed is plotted on the abscissa 33. The torque is plotted on the ordinate 34. Three tractive force curves are shown, each with a different battery charge level (SOC1, SOC2, SOC3) while maintaining a constant magnet temperature of the electric motor's permanent magnets. Due to the different battery charge levels (SOC1, SOC2, SOC3), a different voltage is available to the electric motor. The state shown is when the method according to the invention is not used.

[0036] The first tensile force curve relating to the first state of charge SOC1 is shown as an example for a magnet temperature of 100°C and a voltage of 750V. The second tensile force curve relating to the second state of charge SOC2 is shown as an example for a magnet temperature of 100°C and a voltage of 650V. The third tensile force curve relating to the third state of charge SOC3 is shown as an example for a magnet temperature of 100°C and a voltage of 520V. The numerical values ​​are purely exemplary and should not be understood as limiting.

[0037] The diagram shows that when the state of charge SOC1, SOC2, SOC3 decreases and thus when the voltage available to the electric motor decreases, but the magnet temperature remains the same, there is a drop in the pulling force.

[0038] Fig. 4 shows a schematic representation of the method 100 for adaptively setting a shift point P of the multi-speed powershift transmission of the work machine from Fig. 1.

[0039] In a first step 110 of the method 100, the tractive force Z that must be present during shifting operations S of the multi-speed powershift transmission 4 is specified. Preferably, the specified tractive force Z is the maximum tractive force Z that can be available to the work machine.

[0040] In a second step 120 of method 100, a state variable G of the electric drive system is determined. This state variable G can, for example, be the state of charge (SOC) of the battery.

[0041] In a third step 130 of the method 100, based on the state variable G and the predetermined tractive force Z, a travel speed v of the work machine is determined, at which the predetermined tractive force Z is essentially maintained during the switching process S. This travel speed v is calculated by the control device of the work machine in real time during operation of the work machine based on the state variable G and the predetermined tractive force Z.

[0042] In a fourth step 140 of the method 100, the switching point P is determined at this determined driving speed v.

[0043] In a fifth step 150 of the method 100, the switching operation S is carried out at the switching point P when the work machine has the determined travel speed v. In other words, the switching operation S is carried out when the current travel speed of the work machine reaches the value of the determined travel speed v of the work machine.

[0044] Method 100 runs repeatedly and continuously during operation of the working machine. In other words, the respective switching point S is always determined adaptively depending on the determined value of the state variable G. Reference symbol 1 work machine 2 electric drive system 3 Battery 4 multi-speed powershift transmissions 5 Electric motor 6 Control device 7 Speed ​​sensor 30 Ordinate - Tensile force 31 Abscissa - Speed 32 Ordinate - Torque 33 Abscissa - Speed 50 first course 51 second gear 100 procedures 110 first step 120 second step 130 third step 140 fourth step 150 fifth step G state variable P switching point SOC state of charge SOC1 First state of charge SOC2 Second state of charge SOC3 Third state of charge v speed Z traction force

Claims

[1] Method (100) for adaptively setting a shift point (P) of a multi-speed powershift transmission (4) of a work machine (1), wherein the work machine (1) has the multi-speed powershift transmission (4), an electric drive system (2) and a control device (6), wherein the electric drive system (2) has a battery (3) and an electric motor (5), wherein the multi-speed powershift transmission (4) is operatively connected to the electric drive system (2), wherein the control device (6) is signal-effectively connected to the electric drive system (2) and the multi-speed powershift transmission (4), characterized by , that - a tractive force (Z) which must be present during gearshift operations (S) of the multi-speed powershift transmission (4) is specified, this tractive force (Z) being specified as the maximum tractive force (Z), - a state variable (G) of the electric drive system (2) is determined, wherein the state variable (G) is designed as a state of charge (SOC; SOC1; SOC2; SOC3) of the battery (3) of the electric drive system (2), - based on the state variable (G) and the predetermined tractive force (Z), a driving speed (v) of the working machine (1) is determined at which the predetermined tractive force (Z) is essentially maintained during the switching process (S), - the switching point (P) is set at this determined driving speed (v) - the switching operation (S) is carried out at the switching point (P) when the working machine (1) has the determined driving speed (v). [2] Method (100) according to claim 1, characterized by that the specified pulling force (Z) is exactly maintained during the switching process (S). [3] Control device (6) for a work machine (1), comprising means for carrying out the steps of the method (100) according to one of claims 1 to 2, wherein the control device (6) can be connected to the multi-speed powershift transmission (4) and the electric drive system (2) of the work machine (1) in a signal-effective manner. [4] Computer program product comprising instructions which, when the program is executed by a control device (6) according to claim 3, cause the control device (6) to carry out the method (100) according to one of claims 1 to 2. [5] Work machine (1) comprising a multi-speed powershift transmission (4), an electric drive system (2) and a control device (6) according to claim 3, wherein the control device (6) is connected in a signal-effective manner to the multi-speed powershift transmission (4) and to the electric drive system (2).

Images