Method for operating a drive unit of a working machine

Abstract

The invention relates to a method for operating a drive unit (1) for a working machine (100). The drive unit (1) comprises a motor (2) and a power-split transmission (3) with a variator (5) for stepless adjustment of a transmission ratio (3). The method includes determining (I) a target motor speed (n), receiving (II) a current motor load (L) of the motor (2), and determining (III) an accelerator pedal position (P) based on the determined target motor speed (n) and the received motor load (L). Furthermore, the method includes outputting the determined accelerator pedal position (P) to the motor (2).

Description

Technical field

[0001] The present invention relates to a method for operating a drive unit of a working machine. Furthermore, the present invention relates to a control unit configured to carry out such a method, to a drive unit with such a control unit, and to a working machine with such a drive unit. State of the art

[0002] In the field of construction machinery, drive systems with a motor and a power-split transmission are used. Such power-split transmissions can have a variator, allowing the transmission ratio to be continuously adjusted. The motors of such drive systems can offer different control options, for example, control via an accelerator pedal position and, alternatively or additionally, control via a target motor speed. Different types of motor speed control can be stored within the motor to accommodate these different control options. Description of the invention

[0003] The present invention relates to a method for operating a drive unit for a working machine. The working machine can be a construction, agricultural, or forestry machine. For example, the working machine is a wheel loader. The drive unit comprises a motor and a power-split transmission. The motor can be an internal combustion engine and, alternatively or additionally, an electric motor. The power-split transmission can be a hydrostatic-mechanical transmission and, alternatively or additionally, an electromechanical transmission. The power-split transmission can have a mechanical power branch and a hydrostatic power branch, and, alternatively or additionally, an electric power branch. The power-split transmission includes a variator to allow stepless adjustment of the transmission ratio.For example, the power-split transmission can be designed so that different fixed gear ratios between an input and an output of the transmission can be selected via a mechanical power branch. These different gear ratios can correspond to the operating ranges of the machine. Within these operating ranges, the gear ratio can be continuously adjusted by means of the variator. The variator can be designed as a hydrostatic unit and comprise two hydraulic motors that can be hydrodynamically interconnected. Alternatively or additionally, the variator can also comprise two electric motors that can be electrically interconnected.

[0004] The procedure involves determining a target motor speed. This target speed can be the speed to which the motor is to be regulated. It can be determined based on various state variables of the drive system and, alternatively or additionally, on a drive system strategy. The target motor speed can be determined in such a way that the drive system can be operated as efficiently as possible and, alternatively or additionally, at particularly high power. The target motor speed can be determined by a control unit that is functionally and, alternatively or additionally, physically separate from the motor. Besides determining the target motor speed, the control unit can also perform other tasks within the drive system.Alternatively, the target motor speed can also be determined by a control unit that is functionally and, alternatively or additionally, physically assigned to the motor of the drive unit. The target motor speed can be in a range between 0 rpm and 3000 rpm, for example between 0 rpm and 2500 rpm, or in one embodiment between 500 rpm and 2500 rpm.

[0005] Furthermore, the procedure includes receiving a current engine load. At a specific engine speed, the engine load can be proportional to the engine's torque output and thus describe the engine's utilization.

[0006] For example, the motor load can be expressed as a percentage, indicating what percentage of the maximum power available at the given speed is currently being delivered. The received motor load can therefore be a value between 0% and 100%. The motor load can depend on the current operating conditions of the machine, such as the resistances encountered by the machine. The current motor load can be received as a direct value. Alternatively or additionally, one or more values ​​can be received that are related to the motor load in a predefined way.

[0007] Furthermore, the procedure includes determining an accelerator pedal position based on the determined target engine speed and the received engine load. In this step, an accelerator pedal position can be determined based on the determined target engine speed and the current engine load, resulting in an engine speed corresponding to the target engine speed. The accelerator pedal position can be a value between 0% and 100% and correspond to a percentage of accelerator pedal depressor. The procedure also includes sending the determined accelerator pedal position to the engine. Based on this determined accelerator pedal position, the engine can then regulate its speed. As described above, the accelerator pedal position in this procedure can be determined such that the resulting engine speed corresponds to the determined target engine speed.

[0008] The present method allows an existing control option for an engine via an accelerator pedal position to be used, even though a target engine speed is to be regulated. For example, despite the intended engine speed control, the control logic provided by the engine can be used when the accelerator pedal is actuated. This is advantageous when the control logic provided by the engine during accelerator pedal actuation is beneficial for a drive unit with a power-split transmission including a variator. As a result, the method of the present invention allows the use of an engine control logic optimized for a power-split transmission with a variator. For example, it is advantageous to use an engine speed control system with a proportional controller in a power-split transmission with a variator.Only in this way can stable engine speed control suitable for a power-split transmission with a variator be provided. A proportional controller can be understood as a controller that has a proportional component. In addition, the controller can also have an integral component and, alternatively or additionally, a differential component. In one embodiment, the proportional controller is a pure proportional controller that has neither an integral nor a differential component. If, for example, the engine only provides a proportional control via an accelerator pedal control, the engine can be controlled via the accelerator pedal control to utilize the proportional controller, even though engine speed control is actually intended.

[0009] In one embodiment, receiving the current engine load involves receiving the engine load from the engine's engine control unit. For example, the engine can transmit the current engine load via its engine control unit to a signal transmission device, such as a CAN bus. The current engine load can be transmitted to the CAN bus by the engine control unit continuously and, alternatively or additionally, at specific times. The engine control unit can be a control device that is both functionally and spatially assigned to the engine. The engine control unit can be responsible for controlling the engine torque and, alternatively or additionally, the engine speed.

[0010] In one embodiment, determining the target engine speed involves determining the target engine speed by a transmission control unit of the drive system. For example, the target engine speed can be determined by the transmission control unit in such a way that the drive system, for example, the transmission, can be operated as efficiently as possible and, alternatively or additionally, with the highest possible power output. The transmission control unit of the drive system can also control the transmission, for example, by adjusting the transmission ratio depending on the driving situation. The transmission control unit can be provided both functionally and spatially separately from the engine control unit. The transmission control unit can have a motor interface through which it can communicate with the engine control unit, for example, via the CAN bus described above.For example, the transmission control unit can receive information about the current load on the engine from the engine control unit via the CAN bus. Furthermore, the transmission control unit can send the specific accelerator pedal position to the engine control unit via the engine interface and the CAN bus.

[0011] In one embodiment, the accelerator pedal position is determined based on a data set. This data set can be stored in the form of a lookup table or in another format, for example, on the transmission control unit. The data set can assign an accelerator pedal position to a multitude of value pairs consisting of the target engine speed and the engine load. Thus, if the target engine speed and the current engine load are known, a corresponding accelerator pedal position can be determined from the data set. The data set can be engine-specific. For example, the data set is created before the drive system is operated as intended, which in one embodiment can be achieved through various measurement series on a test bench and, alternatively or additionally, through simulation. The data set can be configured to assign a unique accelerator pedal position to each value pair consisting of the target engine speed and the current engine load.Furthermore, the data set can be configured such that when a specific accelerator pedal position is transmitted to the engine, the engine is automatically adjusted to the target engine speed. By providing such a data set, the accelerator pedal position required to achieve a specific target engine speed can be determined in a simple and effective manner.

[0012] In one embodiment, determining the accelerator pedal position includes limiting it to a position that corresponds to a permissible maximum engine speed. For example, if the engine is not permitted to operate above a permissible maximum speed, then, within the scope of this embodiment, only those accelerator pedal positions can be determined that, when transmitted to the engine, result in engine speeds lower than the permissible maximum speed. If, for example, the determined target engine speed is higher than the permissible maximum speed, the target engine speed can be limited to the permissible maximum speed. In this case, an accelerator pedal position is determined that corresponds to the permissible maximum engine speed and the current load on the engine.This design ensures that the engine does not rotate at a speed above the permissible maximum speed, even when the accelerator pedal is activated.

[0013] Furthermore, the present invention relates to a control unit that is configured, i.e., specifically prepared, for example, programmed, to execute a method according to one of the embodiments described above. The control unit can have one or more interfaces for communicating with the respective components of the drive unit, each of which can be configured as an input and / or output interface. The control unit can be a transmission control unit as described above. Regarding the configurations and advantages of the individual features, reference is made to the above descriptions in connection with the method for operating the machine.

[0014] Furthermore, the present invention relates to a drive unit comprising a motor and a power-split transmission with a variator for stepless adjustment of the transmission ratio. The drive unit also includes a control unit according to the embodiment described above, which, as described above, can be configured as a transmission control unit. The drive unit can also include an engine control unit for receiving the accelerator pedal position, for example, from the transmission control unit. The engine control unit can be configured to regulate the engine speed based on the received accelerator pedal position via a proportional controller. Alternatively, the engine control unit can be configured to regulate the engine speed based on a received target engine speed and a controller other than a proportional controller.In other words, in this embodiment, a proportional controller can be provided by the motor solely via the accelerator pedal control. Furthermore, the present invention relates to a machine with such a drive device. Regarding the configurations and advantages of the individual features, reference is made to the above descriptions in connection with the method for operating the machine. Brief description of the characters Fig. Figure 1 schematically shows a working machine according to one embodiment. Fig. Figure 2 schematically shows a drive unit of the working machine. Fig. 1. Fig. Figure 3 schematically shows a flowchart of a procedure for operating the drive device. Fig. 2 according to one embodiment. Fig. 4 illustrates a data set of the drive unit from Fig. 2 for determining an accelerator pedal position according to an embodiment. Detailed description of embodiments

[0015] Fig. Figure 1 shows a working machine 100 with a drive unit 1 according to an embodiment of the present invention. The working machine 100 comprises a plurality of wheels (not shown) that can be driven via the drive unit 1. The drive unit 1 comprises a motor 2, which in the present embodiment is designed as an internal combustion engine. Furthermore, the drive unit 1 comprises a power-split transmission 3 with a mechanical power path 4 and a hydraulic power path having a variator 5. The power-split transmission 3 has an input 6 and an output 7. The input 6 is mechanically connected to the motor 2. The output 7 of the power-split transmission 3 is mechanically connected to the wheels (not shown) of the working machine 100.The output speed of the drive unit 1 at output 7 is in a fixed relationship with the speed of the wheels and thus with the driving speed of the working machine 100.

[0016] Via the mechanical power path 4 of the power-split transmission 3, which in the present embodiment has several switching elements (not shown), different fixed gear ratios and thus different driving ranges can be selected between the input 6 and the output 7 of the transmission 3. Within these driving ranges, the gear ratio can be continuously adjusted via the variator 5. In the present embodiment, the variator 5 is designed as a hydrostatic drive with two hydraulic machines that are hydraulically interconnected. By adjusting the displacement volume of the variator 5, the gear ratio of the hydraulic power path, and thus also the gear ratio of the transmission 3, can be continuously adjusted. Furthermore, the drive unit 1 includes a control unit 8 for controlling the drive unit 1, which in this embodiment is designed as a transmission control unit.The control unit 8 includes a motor interface 9 for controlling the motor 2. Furthermore, the control unit 8 includes a transmission interface 10 for controlling the power-split transmission 3, among other things for switching the driving ranges of the mechanical power branch 4 and for adjusting the variator 5 of the hydraulic power branch.

[0017] Furthermore, the drive unit 1 comprises a motor control unit 11 with an input interface for receiving a control variable from the transmission control unit 8. The input interface of the motor control unit 11 is electronically connected to the motor interface 9 of the transmission control unit 8 via a CAN bus. The motor control unit 11 is configured to regulate the motor speed of the motor 2 based on the control variable supplied to the input interface via the CAN bus. In the present embodiment, the motor control unit 11 is designed such that a target motor speed n can be specified to it via the CAN bus. Based on this target motor speed n received via the input interface, the motor control unit 11 regulates the motor speed of the motor 2. This regulation is based on a controller that is not a proportional controller.Furthermore, the engine control unit 11 is configured to receive an accelerator pedal position P from the transmission control unit 8 as a control variable via its input interface. Based on the received accelerator pedal position P, the engine control unit 11 then regulates the engine speed of the engine 2. This regulation is based on a proportional controller, i.e., a controller that has at least a proportional component. In the present embodiment, this is a pure proportional controller, which has only a proportional component and no integral or differential components. The engine control unit 11 is also configured to output the current engine load L applied to the engine 2 via the CAN bus.

[0018] The transmission control unit 8 contains a data set that assigns a specific accelerator pedal position P to each pair of values ​​consisting of the target engine speed n and the engine load L. This data set is located in Fig. Figure 4 is schematically illustrated. In the present embodiment, the data set stored on the transmission control unit 8 assigns target engine speeds n between 800 rpm and approximately 2100 rpm and engine loads between 0% and 100%, and an accelerator pedal position P between 0% and 100%. If the target engine speed n and the current load L applied to the engine 2 are known, the following can therefore be determined based on the data set in Figure 8: Fig. In the data set shown in section 4, a unique accelerator pedal position P can be determined from the data set. The in Fig. The data set shown in section 4 is specifically designed for motor 2 of the drive unit 1. If a specific target motor speed n is to be achieved with motor 2, the motor control unit 11 must be provided with the following information via the input interface: Fig. Four derived pedal positions, P, which in turn depend on the current engine load L, are supplied via the engine interface 9 and the CAN bus. The data set is designed such that the accelerator pedal position P increases with increasing target engine speed n and with increasing engine load L.

[0019] The transmission control unit 8 is configured to perform the following with reference to Fig. The procedures described in section 3 are to be carried out. In a first step I, the transmission control unit 8 determines a target motor speed n. In the present embodiment, this is done based on a driving strategy of the working machine 100 stored in the transmission control unit 8, which specifies a target motor speed n for the motor 2 based on different state variables of the drive unit 1. In a subsequent step II, the transmission control unit 8 now receives the current load L applied to the motor 2 from the motor control unit 11 via the motor interface 9 and the CAN bus. In the present embodiment, the current load L applied to the motor 2 is continuously transmitted to the CAN bus by the motor control unit 11 and can therefore be detected in real time by the transmission control unit 8 via the motor interface 9.

[0020] Based on the determined target engine speed n and the received engine load L, the transmission control unit 8 now determines an accelerator pedal position P in a subsequent step III. For this purpose, the values ​​stored on the transmission control unit 8 and in Fig. The data set shown in Figure 4 is used, which assigns a unique accelerator pedal position P to each pair of values ​​consisting of target engine speed n and engine load L. Determining the accelerator pedal position P (Step III) also includes checking (Step III.1) whether the target engine speed n determined in Step I is greater than a permissible maximum speed n. max of motor 2. If this is the case, then in step III.1 the target motor speed n is reduced to the permissible maximum speed n. max limited. In this step III.1, the accelerator pedal position P is then derived from the data set, which corresponds to the permissible maximum speed n. maxand corresponds to the current engine load L applied to engine 2. This ensures that engine 2 does not operate at a speed higher than its permissible maximum speed n. max turns.

[0021] In subsequent step IV, the transmission control unit 8 outputs the accelerator pedal position P, determined in steps III and III.1, to the engine control unit 11 via the engine interface 9 and the CAN bus. The engine control unit 11 receives the accelerator pedal position P via the input interface and, in subsequent step V, adjusts the engine speed 2 based on the received accelerator pedal position P. The process then returns to step I. Reference sign 1 Drive unit 2 Engine 3 power-split gearbox 4 mechanical power branch 5 variator 6 Drive 7 Drive 8 Transmission control unit 9 Motor interface 10 Gearbox interface 11 Engine control unit I Determine engine target speed II. Capture engine load III Determine accelerator pedal position III.1 Limiting the accelerator pedal position IV. Output accelerator pedal position V Adjusting engine speed P Accelerator pedal position L current engine load n Engine target speed n max permissible maximum speed

Claims

[1] Method for operating a drive device (1) for a working machine (100), wherein the drive device (1) comprises a motor (2) and a power-split transmission (3) with a variator (5) for stepless adjustment of a transmission ratio of the transmission (3), comprising determining (I) a target motor speed (n), receiving (II) a current motor load (L) of the motor (2), determining (III) an accelerator pedal position (P) based on the determined target motor speed (n) and the received motor load (L), and outputting (IV) the determined accelerator pedal position (P) to the motor (2). [2] Method according to claim 1, characterized by , that receiving (II) the current motor load (L) of the motor (2) includes receiving the motor load (L) from a motor control unit (11) of the motor (2) of the drive unit (1). [3] Method according to claim 1 or 2, characterized by, that determining (I) the target motor speed (n) includes determining the target motor speed (n) by a transmission control device (8) of the drive device (1). [4] Method according to any one of the preceding claims, characterized by , that the determination (III) of the accelerator pedal position (P) is based on a data set which assigns an accelerator pedal position (P) to a multitude of pairs of values ​​of engine target speed (n) and engine load (L). [5] Method according to any one of the preceding claims, characterized by , that determining (III) the accelerator pedal position (P) includes limiting (III.1) the accelerator pedal position (P) to an accelerator pedal position (P) that corresponds to a permissible maximum engine speed (n) max ) of the motor (2) corresponds. [6] Control device (8) configured to perform a method according to any of the preceding claims. [7] Drive unit (1) comprising a motor (2), a power-split transmission (3) comprising a variator (5) for stepless adjustment of a transmission ratio of the transmission (3) and a control unit (8) according to claim 6. [8] Drive device (1) according to claim 7, characterized by , that the drive device (1) has an engine control device (11) for receiving the accelerator pedal position (P), wherein the engine control device (11) is configured to regulate the engine speed of the engine (2) based on the received accelerator pedal position (P) via a proportional controller. [9] Drive device (1) according to claim 8, characterized by , that the motor control device (11) is further configured to regulate the motor speed of the motor (2) based on a received motor setpoint speed (n) and a controller other than a proportional controller. [10] Working machine (100) with a drive device (1) according to one of claims 7 to 9.

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