Method for operating a power take-off shaft of a working machine, computing unit and working machine

Abstract

The invention relates to a method for operating a power take-off (PTO) shaft (120) of a working machine (100), wherein the PTO shaft (120) can be driven by means of an electric drive (110, 112), comprising: receiving, in a processing unit, an input signal generated by an input device; controlling, by means of the processing unit, the electric drive, based on the input signal, according to a predetermined special function of the PTO shaft or one of several predetermined special functions of the PTO shaft (120), wherein each of the several predetermined special functions comprises a predetermined movement pattern for the PTO shaft.

Description

[0001] The present invention relates to a method for operating a power take-off shaft of a work machine, wherein the power take-off shaft can be driven by means of an electric drive, a computing unit and a computer program for carrying out the method, as well as such a work machine, e.g. a tractor. Background of the invention

[0002] Work machines, especially mobile work machines such as vehicles or other movable or mobile machines, e.g., tractors, typically have a power take-off (PTO) shaft. Attachments can be attached to this shaft, possibly via a cardan shaft, in order to utilize the power generated by the work machine. Disclosure of the invention

[0003] According to the invention, a method for operating a power take-off shaft of a work machine, a computing unit and a computer program for implementing the method, as well as a work machine with the features of the independent patent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

[0004] The invention relates to power take-off shafts for work machines, in particular mobile work machines such as tractors, and in particular their operation. Power take-off shafts that are driven by an electric drive are considered. The invention will be explained in more detail below using the example of a tractor as a work machine or a tractor's power take-off shaft. However, it is understood that this can be applied to other work machines with a power take-off shaft, e.g., excavators, loaders, other construction machines, or agricultural machines and equipment.

[0005] An attachment can be connected to the PTO of the tractor or other work machine using a cardan shaft, for example, in order to use the mechanical drive energy of the drive unit (e.g. diesel engine or electric drive) of the tractor or work machine. To couple the cardan shaft to a splined shaft profile of the PTO, the PTO or the cardan shaft usually has to be turned by a few degrees so that the gearing of the PTO and cardan shaft can mesh. Depending on the attachment, a cardan shaft that is already connected to the attachment may be difficult or impossible to turn by hand. With diesel-powered PTOs with a engageable intermediate gear, turning the PTO manually is often easier, but this is frequently made more difficult by heavy soiling or the use of lubricants.However, the same behavior occurs with electrified drives with or without a clutchable transmission.

[0006] Furthermore, the PTO shaft in conventional tractors and other work machines is usually fixed in speed, meaning the PTO shaft rotates continuously at a constant speed. This generally prevents the PTO from being precisely positioned. This makes it impossible to move the implement or its tools to specific positions, for example, for repair purposes.

[0007] Within the scope of the invention, it is now proposed to generate an input signal by means of an input device such as a button or push button, which is arranged in particular on the outside of the work machine near the power take-off shaft. The input signal is then received, for example in a computing unit, and based on the input signal the electric drive is then controlled according to a predetermined special function of the power take-off shaft or one of several predetermined special functions of the power take-off shaft. The control and further steps can also be carried out via the computing unit. At least in the case of several predetermined special functions, one of the several special functions can also initially be determined or selected based on the input signal. The one or each of the several predetermined special functions each comprises a predetermined movement pattern for the power take-off shaft.The electric drive is thus controlled to move the PTO shaft according to the specified movement pattern of the specific specified special function.

[0008] A special function is understood in particular to be a function which is different from a regular function (or regular operation), in which the PTO shaft is continuously moved or rotated at a certain speed. The movement patterns of the special functions include, in particular, the PTO shaft being moved at a maximum speed which is below - in particular significantly below - a speed in regular operation at which the attachment is driven for its usual purpose. Speeds which could be considered for such a special function could be, for example, speeds of less than 30 rpm or even less than 20 rpm, although the actual speed can then also depend in particular on the special function.

[0009] In one embodiment, one or more of the predefined special functions comprise a pendulum function, wherein the predefined movement pattern of the pendulum function comprises alternating rotation of the PTO shaft in one and the opposite direction. In other words, the PTO shaft then moves or rotates back and forth. A speed for this or a PTO speed profile can also be specifically specified. This makes it easier for a user to couple an attachment or a cardan shaft to the PTO shaft or its splined shaft.

[0010] Preferably, a stop signal is also received from the input device. This stops the electric drive and stops the PTO shaft from moving. This allows normal operation to be returned after the attachment or PTO shaft is connected.

[0011] The input signal can, for example, be a signal indicating a single, short press of the button. The stop signal can also be a signal indicating a single, short press of the button.

[0012] In one embodiment, one or more of the predefined special functions comprises a positioning function, wherein the predefined movement pattern of the positioning function comprises moving the power take-off shaft to a predefined or predeterminable target position or rotating the power take-off shaft by a predefined or predeterminable angle. In this way, a specific position can be targeted, or the power take-off shaft can be rotated by a specific angle. This allows a user, for example, to move the attachment to a specific position, e.g., for repair purposes.

[0013] Preferably, a position or angle signal is also received from the or another input device, e.g., an HMI (Human Machine Interface, e.g., a touch display), particularly before receiving the input signal. The target position or angle is then determined based on the position or angle signal.

[0014] The input signal here can, for example, be a signal that indicates a single, short press of the button. However, to distinguish between the oscillating function and the positioning function, the input signal here can also be a signal that indicates a double, short press of the button. It goes without saying that the types of input signals for the oscillating function and the positioning function can also be swapped. It is also conceivable to switch between the oscillating function and the positioning function in another way, e.g. via the other input device, e.g. the HMI. In this case, when the button is pressed, the currently selected special function is executed.

[0015] In one embodiment, the one or more predefined special functions comprise a continuous motion function, wherein the predefined movement pattern of the continuous motion function comprises rotating the PTO shaft in a predefined or predeterminable direction as long as the input signal is received. This allows, for example, a visual or optical check by the user as to when the PTO shaft has reached a desired position.

[0016] Preferably, a direction signal is also received from the or another input device, e.g., the HMI, in particular before receiving the input signal. The direction is then determined based on the direction signal.

[0017] The input signal can, for example, be a signal indicating whether the button is pressed or not. For example, while the button is pressed, a continuous or quasi-continuous signal can be generated as the input signal, which ends as soon as the button is released.

[0018] In one embodiment, monitoring of a torque and / or a speed of the PTO is further provided. If the torque and / or the speed exceed a respective predetermined or predefinable limit value, the control of the electric drive is stopped in order to stop the PTO from moving. This can, for example, serve for safety reasons in order to avoid hazards in the event of the PTO or the attachment blocking. However, it can also be used, for example, to ensure that the pendulum function stops automatically as soon as the cardan shaft is applied to the PTO (sufficiently far). The aforementioned limit values ​​can be specified in a suitable manner, e.g. by the manufacturer, or can also be selected specifically, e.g. via the HMI.

[0019] If the electric drive does not have an angle sensor, encoder system, rotary encoder or other sensor for detecting a position, angle or speed, sufficient accuracy can also be achieved using a sensorless method for controlling the electric drive.

[0020] The method according to the invention can therefore be used, for example, in electrified tractors or other work machines which, in particular, have a drive train independent of the power take-off shaft. Using a drive-controlled oscillating function of the power take-off shaft drive train, the power take-off shaft can be moved clockwise and counterclockwise by a few degrees, for example, at low speed, in order to make it easier for the tractor driver or other user to couple the cardan shaft. The oscillating movement is triggered, for example, by a push button mounted near the power take-off shaft. To safeguard the movement (protect the tractor driver or user), the maximum speed and maximum torque of the oscillating movement are monitored, in particular.

[0021] Another embodiment enables the positioning of the PTO shaft using a function that converts the usually speed-controlled drive into a positioning drive and moves the PTO to an angular position specified via the control element or HMI. If the target position is unknown, the PTO shaft can be moved at a slow speed, for example, using a jog mode (continuous motion function) until the desired target angle is visually reached. The push button for the pendulum movement can also be used for this purpose (e.g., pressing it for a longer time starts the movement).

[0022] Speed ​​and torque can be monitored in both jog mode and positioning mode.

[0023] A computing unit according to the invention, e.g. a control unit of an electric drive of a work machine, is configured, in particular in terms of programming, to carry out a method according to the invention.

[0024] The invention also relates to a work machine with an electric drive, a power take-off shaft which can be driven by means of an electric drive, with at least one input device, e.g. a push button and an HMI, and with a computing unit according to the invention.

[0025] Implementing a method according to the invention in the form of a computer program or computer program product with program code for performing all method steps is also advantageous, as this entails particularly low costs, especially if an executing control unit is also used for additional tasks and is therefore already present. Suitable data storage devices for providing the computer program include, in particular, magnetic, optical, and electrical storage devices, such as hard disks, flash memories, EEPROMs, DVDs, and others. Downloading a program via computer networks (Internet, intranet, etc.) is also possible.

[0026] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0027] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0028] The invention is illustrated schematically in the drawing using exemplary embodiments and is described in detail below with reference to the drawing. Character description Fig. 1 shows schematically a working device for explaining the invention. Fig. 2 shows schematically a sequence of a method according to the invention in one embodiment. Fig. 3a, Fig. 3b, Fig. 3c show diagrams for explaining various functions according to an embodiment. Detailed description of the drawing

[0029] In Fig. 1 schematically shows a working device 100 to explain the invention. The working device 100 is, by way of example, a tractor. The tractor 100 has an electric drive with an electric machine or an electric motor 110 and an inverter 112, as well as a computing unit 114 designed as a control unit for controlling the electric drive. The tractor 100 also has a power take-off shaft 120 (here, for example, a rear power take-off shaft) which can be driven by means of the electric drive 110, 112. In particular, the electric drive 110, 112 can be an independent drive train specifically for the power take-off shaft 120, i.e., one independent of other driven components such as wheels.

[0030] Furthermore, the tractor 100 has an input device 130 designed as a push button, which is arranged, for example, at the rear or rear area of ​​the tractor 100, in particular near the power take-off shaft (e.g., less than 2 m from the power take-off shaft 120). Furthermore, the tractor 100 has an input device 140 designed as an HMI, e.g., a touch display, which is arranged, for example, in the driver's cab of the tractor 100.

[0031] Furthermore, an attachment 150 with a universal joint shaft 152 is shown, which can be coupled to the power take-off shaft 120 of the tractor 100 if necessary. As shown, the power take-off shaft 120 has a splined shaft onto which the universal joint shaft 152 (which is correspondingly designed with a splined shaft profile) can be mounted or slid. As mentioned, this often requires a slight rotation of the power take-off shaft 120 or the universal joint shaft 152.

[0032] In Fig. 2 schematically shows a sequence of a method according to the invention in one embodiment. In step 200, for example, the push button is first actuated, whereby an input signal 202 is generated. This input signal 202 is then received, for example, in the control unit, in step 204. Based on the input signal 202, one of several predetermined special functions 208a, 208b, 208c of the PTO is then selected or determined, in step 206. As mentioned, a distinction can be made between the functions, for example, based on the type of input signal. Likewise, the special function can be determined, for example, based on further specifications. Each of these special functions comprises a predetermined movement pattern 210a, 210b, 210c for the PTO.

[0033] The several specified special functions include, for example, a pendulum function 208a, a positioning function 208b, and a continuous movement function 208c; these special functions are intended to be Fig. 3a, Fig. 3b, Fig. 3c will be explained in more detail.

[0034] Based on the input signal 202, the electric drive is then controlled in step 212 to move the PTO shaft according to the predetermined movement pattern of the specific predetermined special function.

[0035] Depending on the type of special function, for example, a stop signal 216 may be received in step 214. The control of the electric drive is then stopped in step 218. It may also be provided that a position or angle signal 220 or a direction signal 222 is received before the input signal 202 in order to specify a position, angle, or direction.

[0036] Likewise, step 224 may provide for monitoring of a torque and / or a speed of the PTO shaft in order to stop the activation of the electric drive, step 226, if the torque and / or the speed exceed a respective predetermined or predeterminable limit value.

[0037] In the Fig. 3a, Fig. 3b, Fig. 3c shows diagrams for explaining various special functions according to an embodiment. The diagram in Fig. 3a the pendulum function 208a, the diagram in Fig. 3b the positioning function 208b, and the diagram in Fig. 3c shows the continuous motion function 208c. Here, a rotational speed n is plotted against a time t.

[0038] If the pendulum function (also known as pendulum operation), cf. Fig. 3a, selected and started, the PTO executes a trapezoidal movement pattern, taking the speed and torque limits into account. The PTO is initially accelerated in a predefined direction before performing a smooth rotational movement and decelerating again in a defined manner. The speed reached here is n1. A speed limit n_max is also shown as an example, which must not be exceeded and at which, for example, the system is stopped.

[0039] Subsequently, and without interruption, this movement pattern is executed in the opposite direction, before the described process is repeated until it is manually terminated or one of the applied limits is exceeded. For example, an acceleration is denoted by n1'; the deceleration can be the same or a different amount.

[0040] The resulting movement corresponds to a pendulum motion. One period of the pendulum motion is denoted here by Δt. Both manual starting and stopping of the PTO movement can be initiated by pressing the push button located nearby. The start direction can be set using the HMI in the driver's cab.

[0041] The positioning function (also called positioning mode), see Fig. 3b, can also be started and stopped using the dedicated push button. The angle difference that the PTO should cover in a given time can be set, for example, via the HMI in the driver's cab. Fig. 3b, instead of the angle difference, a time difference Δt is shown due to the time diagram, which, however, corresponds to an angle difference via the speed. The direction or rotational direction of the PTO can also be defined in this way. This operating mode, for example, is also subject to defined speed and torque limits. If the limits are exceeded, the movement of the PTO and the execution of the movement pattern are terminated. The speed reached here is n2. Over the period of time, e.g. from acceleration, deceleration and constant travel (Δt Beschl , Δt Verzög , t Konst ) the angle difference Δϕ results from the currently acting speed n, e.g. Δϕ = 1 / 2*2*π*n'*Δt Beschl *Δt Beschl + 2*π*n*t Konst + 1 / 2*2*π*n'*Δt Ver-zög *Δt Verzög . In addition, the speed limit n_max is shown again as an example, which must not be exceeded and at which, for example, the system is stopped.

[0042] After starting, e.g., by pressing the push button, the PTO is accelerated evenly until it experiences a uniform movement at speed n2 and is finally decelerated in a defined manner to reach the specified target position. Pressing the push button again, for example, can also terminate the movement that has already started. For example, a deceleration is designated n2'; the acceleration can be the same or a different amount.

[0043] To control the motion of the function, a rotary encoder, angle sensor, or other sensor system can be used to evaluate the actual angle of the PTO shaft. If an angle sensor is not available due to space and / or cost constraints, the actual angle can be evaluated using a sensorless control system (sensorless positioning, e.g., via signal injection in the electric motor).

[0044] The continuous motion function (also known as jog mode), see Fig.3c, can also be started and stopped using the push button provided. The angle difference covered is determined by the user by holding the push button down until the desired target position is reached. If the push button is released, the PTO movement is stopped with a defined deceleration. The speed reached here is n3. In addition, the speed limit n_max is shown again as an example, which must not be exceeded and at which, for example, a stop is made. For example, an acceleration is designated n3', while the deceleration is designated n4'; the deceleration here is significantly greater in magnitude than the acceleration in order to achieve a quick stop. Typically, the deceleration (or deceleration ramp) defined by the manufacturer is defined with a steeper gradient than the acceleration (acceleration ramp).

[0045] The direction of rotation can be set by the operator via the HMI in the driver's cab. Even in this mode, the PTO can be subject to predefined speed and torque limits. If these limits are exceeded, the PTO movement is terminated in a defined manner.

[0046] The functions are implemented, for example, in the control unit for the converter (or inverter), which controls the electric machine. Software algorithms are typically used here. Control is achieved via (angle), speed, and torque control. Cascaded control of electric motors is common practice.

[0047] The special function (e.g., oscillation, positioning, or continuous motion function) is converted into angle, speed, and / or torque setpoints (profile generation) using algorithms based on defined parameters such as angle, speed, acceleration, and deceleration. The setpoints are fed into the drive control system, resulting in the shaft of the electric motor or the PTO shaft producing the desired actual values.

[0048] The inverter control unit receives the signals from the push button or the HMI control, either directly via digital input signals or fieldbus communication, or via the tractor control unit, which may have an HMI communication connection and a push button connection. The inverter control unit is in turn connected to the tractor control unit via a fieldbus, for example. The implementation of the described operating modes (profile generation) can also take place in the tractor control unit as a computing unit, whereby only angle, speed, or torque setpoints are transmitted to the inverter control unit.

[0049] In summary, it should be noted that the oscillating motion can be initiated by pressing a button once, which starts the oscillating motion. This leaves the tractor driver with both hands free to position and connect the drive shaft to the PTO. The oscillating motion can be initiated near the PTO, allowing for effortless coupling. Manual movement and touching of the PTO are not required. The tractor manufacturer can define the characteristic parameters of the motion, for example, and the speed and torque can be monitored.

[0050] With the positioning function, any position can be specified by the tractor driver via the HMI. This simplifies repairs or inspects the attachment's tools, and no manual effort is required. The tractor manufacturer can define the movement parameters, for example, and speed and torque can be monitored.

[0051] In inching mode, the tractor driver can move to any desired position. Inching mode is particularly suitable for tractor drivers near the PTO, and no manual effort is required. The direction of rotation, for example, can be set via the HMI. The tractor manufacturer, for example, can define the movement characteristics, and speed and torque can be monitored.

Claims

[1] Method for operating a power take-off shaft (120) of a work machine (100), wherein the power take-off shaft (120) is drivable by means of an electric drive (110, 112), comprising: Receiving (204), in a computing unit, an input signal (202) generated by an input device; Controlling (212), by means of the computing unit, the electric drive, based on the input signal (202), according to a predetermined special function of the power take-off shaft or one of several predetermined special functions (208a, 208b, 208c) of the power take-off shaft (120), wherein the one or each of the several predetermined special functions each comprises a predetermined movement pattern (210a, 210b, 210c) for the power take-off shaft. [2] The method of claim 1, wherein the one or more predetermined special functions comprises a pendulum function (208a), and wherein the predetermined movement pattern (210a) of the pendulum function comprises alternating rotation of the PTO shaft in one and in an opposite direction. [3] The method of claim 2, further comprising: Receiving (214) a stop signal (216) from the input device; and Stopping (218) the actuation of the electric drive to stop the movement of the PTO shaft. [4] Method according to one of the preceding claims, wherein the one or one of the several predetermined special functions comprises a positioning function (208b), and wherein the predetermined movement pattern (210b) of the positioning function comprises moving to a predetermined or predeterminable target position by the power take-off shaft or rotating the power take-off shaft by a predetermined or predeterminable angle. [5] The method of claim 4, further comprising: Receiving a position or angle signal (220) from the or another input device, in particular before receiving the input signal; Determine the target position or angle based on the position or angle signal. [6] Method according to one of the preceding claims, wherein the one or one of the several predetermined special functions comprises a continuous motion function (208c), and wherein the predetermined motion pattern (210c) of the continuous motion function comprises rotating the PTO shaft in a predetermined or predeterminable direction as long as the input signal is received. [7] The method of claim 6, further comprising: Receiving a direction signal (222) from the or another input device, in particular before receiving the input signal; Determine the direction based on the direction signal. [8] A method according to any one of the preceding claims, further comprising: Monitoring a torque and / or a speed (n) of the PTO shaft; and Stopping the control of the electric drive to stop the movement of the PTO shaft when the torque and / or the speed exceed a respective specified or specifiable limit value (M_max, n_max). [9] Method according to one of the preceding claims, further comprising: generating (200) the input signal (202) by means of the input device, wherein the input device is arranged on the outside of the work machine within a predetermined area around the power take-off shaft, in particular at a distance of less than 2 m from the power take-off shaft. [10] Computing unit (114) comprising a processor configured to execute the steps of a method according to any one of the preceding claims performed by the computing unit. [11] Work machine (100) with an electric drive (110, 112), a power take-off shaft (120) which can be driven by means of the electric drive, with at least one input device (130, 140) and with a computing unit (114) according to claim 10. [12] A computer program comprising instructions which, when executed by a computer, cause the computer to carry out the method according to claims 1 to 9. [13] A computer-readable data carrier on which the computer program according to claim 12 is stored.

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