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 magnet temperature (T; T1; T2; T3) of the permanent magnets of the electric motor (5) 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 determining a shift point of a multi-speed powershift transmission of a working machine, a control device, a computer program product and a working machine.

[0002] A gear shift, particularly a downshift in a multi-speed powershift transmission of a machine, requires additional power from the machine's driving motor to compensate for rotor inertia. In battery-electric machines, the driving motor is an electric motor. The drive trains of these machines can include an electric motor and a mechanically connected transmission with at least two gear stages. A suitable gear can be selected based on the driving requirements and the electric motor's performance map. Significant overlap between gears is possible with regard to the machine's speed and tractive force.

[0003] From EP 0 339 202 A2 a drive device for machines and vehicles is known in which a special shifting behavior is achieved when downshifting into a lower gear.

[0004] DE 10 2020 001 600 A1 discloses 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, through which the motor vehicle can be electrically driven by means of the traction machine, wherein the gear change is carried out depending on a current electrical voltage of the energy storage device.

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

[0006] DE 195 15 534 A1 relates to a control device for an automatic transmission and a control method for the automatic transmission, wherein shifting without a shift routine directory is possible 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 stepped automatic transmission controlled by a transmission control unit.

[0008] DE 101 17 162 A1 discloses an electronic transmission unit for gear shift control in a motor vehicle, which is connected to an electronic engine unit for controlling an internal combustion engine. The transmission unit determines the engine torque corresponding to a specified traction requirement, as well as the engine torque adjustable by the engine unit for the current gear. If the engine torque corresponding to the specified traction requirement cannot be adjusted for the current gear, the transmission unit shifts gears if an engine torque can be adjusted in the new gear that is closer to the engine torque corresponding to the specified traction requirement than the engine torque adjustable in the current gear.

[0009] DE 10 2019 203 730 A1 relates to a method for operating a drive train for a working machine, wherein a working drive of the working machine is driven by a first electric motor via a first gearbox arrangement, wherein a travel drive of the working machine is driven by a second electric motor via a second gearbox arrangement, wherein a speed synchronization of the second electric motor takes place during a switching operation of the second gearbox arrangement and wherein a temperature of the second electric motor is detected.

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

[0011] Starting from the aforementioned problem, the present invention proposes a method for adaptively determining a shift point of a multi-speed powershift transmission of a work machine with the features of claim 1, a control device with the features of claim 3, a computer program product with the features of claim 4, and a work machine with the features of claim 5. Further advantageous embodiments and developments are described in the dependent claims.

[0012] In a method for adaptively determining a shift point of a multi-speed powershift transmission of a working machine, wherein the working machine comprises the multi-speed powershift transmission, an electric drive system, and a control unit, the electric drive system comprising a battery and an electric motor, the multi-speed powershift transmission being operatively connected to the electric drive system, and the control unit being 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 specified. A state variable of the electric drive system is determined. Based on the state variable and the specified tractive force, a travel speed of the working machine is determined at which the specified tractive force is essentially maintained during the shifting operation.The switching point is set at this determined driving speed. The switching process is executed at the switching point when the machine reaches the determined driving speed.

[0013] The working machine can be designed as a vehicle intended for performing at least one work task that is not for transporting persons and / or goods. The working machine can have a work device or tool for this purpose. To power the work device, the working machine can have a drive system. The working machine can be construction machinery and / or agricultural machinery. For example, the working machine can be a wheel loader, a tractor, a concrete mixer, a refuse collection vehicle, a forklift, a refrigerated truck, etc. The working machine can be a conventional or an automated working machine that can be remotely controlled. The automated working machine can be designed as an autonomous working machine.

[0014] The machine has an electric drive system, which in turn includes the battery and the electric motor. The battery is connected to the electric motor in an energy-efficient manner. In this context, "energy-efficiently connected" means that the battery can supply energy to the electric motor 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 regenerative braking mode. The electric motor is preferably a permanent magnet electric motor and serves to drive the machine. The battery acts as 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 drive for the working machine and a second electric motor that can provide an auxiliary drive to operate the working equipment or tool.

[0015] The machine also features a multi-speed powershift transmission. This transmission serves to translate 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 machine can have one or more driven axles. Each driven axle can be connected to and driven by the electric motor via the multi-speed powershift transmission. The multi-speed powershift transmission allows, in particular, 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 machine also includes a control unit. The control unit is preferably designed as an ECU. The control unit is connected to the electric drive system and the multi-speed powershift transmission via a signal-transmitting mechanism. "Connected via a signal-transmitting mechanism" in this context means that the control unit is connected to the multi-speed powershift transmission and the electric drive system in such a way that data and signal exchange can take place. The control unit is configured to select a gear ratio of the multi-speed powershift transmission depending on the shift point defined by the method according to the invention. In other words, the control unit can actuate the multi-speed powershift transmission so that a gear is changed, i.e., shifting up or down.The control unit is also designed to receive and evaluate sensor-acquired data and signals from the electric drive system, i.e., from the battery and / or the electric motor. Furthermore, the control unit has a storage unit on which data can be stored or saved.

[0017] In the first step of the process, the tractive force required during shifting operations of the multi-speed powershift transmission is predefined. This predefined tractive force is stored in the control unit's memory. Traction force, or performance, can refer to the power output of the electric motor that can be delivered in continuous operation. Peak performance can refer to the maximum tractive force available from the electric motor. In this first step, the maximum tractive force is predefined as the tractive force required during shifting operations of the multi-speed powershift transmission. Thus, the maximum tractive force should be available during every shift, so that no drop in tractive force is perceptible to the operator of the machine. Consequently, the tractive force is kept constant during operation, namely at the value of the maximum tractive force.

[0018] The state of the electric drive system is determined. This state is determined using suitable sensors and transmitted to the control unit. The respective sensors are thus connected to the control unit, enabling data and signal exchange. The control unit can evaluate the data and / or signals provided by the sensors. Alternatively, the evaluation can be performed directly by the sensors themselves.

[0019] The state variable of the electric drive system is defined as a state variable of the electric motor, e.g., as the magnetic temperature of the electric motor's permanent magnets. This magnetic temperature changes during the operation of the driven machine and thus during the operation of the electric motor over the operating period.

[0020] Based on the state variable and the specified tractive force, the travel speed of the machine is determined at which the specified tractive force is essentially maintained during the shifting process. "Essentially maintained" here means that the tractive force drops only so minimally during the shifting process that this is imperceptible to the operator of the machine. Preferably, the tractive force is maintained exactly during the shifting process and does not drop at all.

[0021] The driving speed is determined by the control unit. Using an algorithm, the control unit calculates, for a given state variable and specified tractive force, the speed at which the shifting process can occur so that the specified tractive force is essentially maintained or even exactly maintained. The shifting point is set by the control unit at this determined driving speed. The shifting process is executed at the shifting point when the machine reaches the determined driving speed. Thus, when the machine reaches the determined driving speed, the shifting process takes place. This allows shifting into a higher or lower gear as needed. The current driving speed is determined by suitable sensors, such as a speed sensor, which are connected to the control unit via a signal.

[0022] For example, if the permanent magnets of the electric motor have a magnetic temperature of 20°C and a predetermined maximum tractive force, switching can occur at, say, 17 km / h. The switching point is thus set at 17 km / h. However, if the magnetic temperature is already 150°C and the maximum tractive force is predetermined, the switching point is shifted towards a lower speed, for example, to 10 km / h. Thus, switching occurs when the machine is traveling at a speed of 10 km / h. The maximum tractive force is essentially maintained. The numerical values ​​are purely illustrative and not intended to be restrictive.

[0023] The advantage of the method presented here is that the drop in tractive force is kept as low as possible or minimized. The tractive force remains the same or nearly the same for the operator of the machine despite the shifting process, and no performance losses have to be accepted. The disadvantages caused by a drop in tractive force, such as unstable handling or insufficient power supply to the working equipment to perform the necessary work, can thus be avoided.

[0024] The control unit for the machine includes means for executing the steps of the procedure already described in the previous description. The control unit can be effectively connected to the multi-speed powershift transmission and the electric drive system of the machine. Therefore, when used in a machine, the control unit is effectively connected to the multi-speed powershift transmission and the electric drive system. This has already been described in the previous description. To establish these connections, the control unit has interfaces through which an effective signal connection can be enabled.

[0025] Furthermore, the control unit is designed in such a way that, when used in a machine, it can be effectively connected to sensors, e.g., to sensors for determining the magnetic temperature of the permanent magnets of the electric motor and to sensors for determining the current speed of the machine. For this purpose, the control unit has at least one additional interface.

[0026] Furthermore, the control unit has a storage unit on which data can be stored or saved. This was also described in the previous description. The control unit can use a computer program to execute the procedure.

[0027] Based on the determined vehicle speed, the control unit activates the multi-speed powershift transmission to initiate a gear shift at that specific speed. This has already been described in the previous section.

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

[0029] The machine has a multi-speed powershift transmission, an electric drive system, and a control unit, which has already been described in the previous description. The control unit is connected to the multi-speed powershift transmission and the electric drive system via a signaling mechanism. This has also already been described. The machine is preferably configured as a wheel loader or a front loader.

[0030] The figures below describe various embodiments and details of the invention in more detail. They show, by way of example: Fig. 1 a schematic representation of a working machine according to an exemplary embodiment, Fig. 2 a schematic representation of a tractive force-speed diagram of the multi-speed powershift transmission of the working machine Fig. 1, Fig. 3 a schematic representation of a torque-speed diagram of the working machine Fig. 1, Fig. 4 a schematic representation of the procedure for adaptively setting a shift point of the multi-speed powershift transmission of the working machine Fig. 1.

[0031] Fig. Figure 1 shows a schematic representation of a working machine 1 according to an exemplary embodiment. The working machine 1 is a wheel loader with a bucket as its working attachment. The working machine 1 has an electric drive system 2. The electric drive system 2 includes a battery 3 and an electric motor 5. The electric motor 5 and the battery 3 are connected to each other for energy transfer. The working 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 working machine is driven by the electric drive system 2, enabling it to move along a path. This is indicated by the longitudinal arrow.

[0032] The machine 1 also has the control unit 6. The control unit 6 is connected to the multi-speed powershift transmission 4 and can control it. The control unit 6 is also connected to the electric drive system 2, specifically to the battery 3 of the electric drive system 2 and to the electric motor 5 of the electric drive system 2. The control unit 6 can query the magnetic temperature of the permanent magnets of the electric motor 5. The control unit 6 can also query the current speed of the machine 1 from a speed sensor 7, to which it is connected. The procedure 100, which is described in [reference missing], runs on the control unit 6. Fig. 5 is shown.

[0033] Fig. Figure 2 shows a schematic representation of a tractive force-speed diagram of the multi-speed powershift transmission of the working machine. Fig. 1. The abscissa 31 represents the speed of the machine. The ordinate 30 represents the tractive force of the machine. The graph shows, as an example, the tractive force versus speed in first gear 50 and in second gear 51. It is clearly evident that there is a larger overlap range between gears 50 and 51. This makes it possible to adaptively select the shift point for changing between gears 50 and 51.

[0034] Fig. Figure 3 shows a schematic representation of a torque-speed diagram of the working machine. Fig. 1. The rotational speed is plotted on the abscissa 33. The torque is plotted on the ordinate 34. Three tensile force curves are shown, each with a different magnetic temperature T1, T2, T3 of the permanent magnets of the electric motor at a constant voltage available to the electric motor. The state shown is that when the method according to the invention is not used.

[0035] The first tensile force curve with respect to the first magnet temperature T1 is shown as an example for a magnet temperature T1 of 20°C and a voltage of 650V. The second tensile force curve with respect to the second magnet temperature T2 is shown as an example for a magnet temperature T2 of 100°C and a voltage of 650V. The third tensile force curve with respect to the third magnet temperature T3 is shown as an example for a magnet temperature T3 of 180°C and a voltage of 650V. The numerical values ​​are purely illustrative and not intended to be restrictive.

[0036] The diagram shows that with increasing magnet temperature T1, T2, T3 and constant voltage, there is a drop in the tensile force.

[0037] Fig. Figure 4 shows a schematic representation of the method 100 for adaptively setting a shift point P of the multi-speed powershift transmission of the working machine. Fig. 1.

[0038] In a first step 110 of the method 100, the tractive force Z, which 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 made available to the working machine.

[0039] In a second step 120 of procedure 100, a state variable G of the electrical drive system is determined. This state variable G can, for example, be the magnetic temperature T of the permanent magnets of the electric motor.

[0040] In a third step 130 of the procedure 100, a travel speed v of the working machine is determined based on the state variable G and the specified tractive force Z, at which the specified tractive force Z is essentially maintained during the switching operation S. This travel speed v is calculated by the control unit of the working machine in real time during the operation of the working machine based on the state variable G and the specified tractive force Z.

[0041] In a fourth step 140 of the procedure 100, the switching point P is determined at this determined driving speed v.

[0042] In a fifth step 150 of procedure 100, the switching operation S is executed at the switching point P when the driven machine has the determined travel speed v. In other words, the switching operation S is executed when the current travel speed of the driven machine reaches the value of the determined travel speed v of the driven machine.

[0043] The procedure 100 runs repeatedly and continuously during the operation of the machine. In other words, the respective switching point S is always adaptively determined depending on the determined value of the state variable G. Reference sign 1 working machine 2 electric drive system 3 batteries 4-speed powershift transmission 5 electric motor 6 Control unit 7 Speed ​​sensor 30 Ordinates - Traction force 31 Abscissa - Velocity 32 Ordinates - Torque 33 Abscissa - Rotational speed 50 first gear 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 T magnetic temperature T1 First magnet temperature T2 Second magnet temperature T3 Third magnetic temperature v speed Z tractive 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 magnet temperature (T; T1; T2; T3) of the permanent magnets of the electric motor (5) 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 determined 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 one of the preceding claims, 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).

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