Method for operating a drive train of a working machine, electrified drive train, and working machine

Abstract

The invention relates to a method for operating a drive train of a working machine, wherein the drive train has a drive motor, a service brake and an assisting brake, wherein there is a drive coupling between the drive motor of the drive train and at least one wheel of the working machine such that a braking torque of the drive motor counteracts a downhill slope force acting on the working machine, wherein automated actuation of the assisting brake is undertaken (103) if the working machine is subject to an impermissible acceleration (102), and wherein the assisting brake is actuated in accordance with a required braking torque (103). The method according to the invention is distinguished in that the assisting brake is also actuated in accordance with a thermal loading of the assisting brake (107, 111), and in that the assisting brake is designed as a spring-pressurized and hydraulically or pneumatically releasable brake. The invention further relates to an electrified drive train and to a corresponding working machine.

Description

[0001] Method for operating a drive train of a work machine, electrified

[0002] Drivetrain and working machine

[0003] The present invention relates to a method for operating a drive train of a work machine according to the preamble of claim 1, an electrified drive train for a work machine according to the preamble of claim 11 and a corresponding work machine.

[0004] In addition to conventionally powered work machines, electrically powered work machines such as wheel loaders, skid steer loaders, telescopic loaders, dump trucks or excavators are also known in the state of the art. Such work machines are either purely electrically powered, i.e. they have only an electric battery or a fuel cell for generating electricity from hydrogen as their energy storage device. Or they are diesel-electric powered, which means that the required energy is provided by a diesel-powered generator and, if necessary, by an electrical buffer storage device, such as an appropriately dimensioned capacitor or a comparatively small battery. In all cases, the mechanical power required for the travel drive and the work drive is provided by one or more drive motors.Furthermore, it is known to use the drive motors of electric drives to recuperate electrical power during braking in generator mode. In addition, a mechanical friction brake is always provided to ensure sufficient braking power at all times for safety reasons.

[0005] In this context, EP 0962 597 A2 describes a battery-operated work machine which has two drive motors for the travel drive and another drive motor for the working drive.

[0006] WO 2008 / 128674 A1 discloses a work machine with a hybrid drive train comprising an internal combustion engine and an electric motor. An electrical energy storage device is provided to supply energy to the electric motor, which can be regeneratively charged by operating the drive motor in generator mode during a braking operation of the work machine.

[0007] DE 10 2020 203 594 A1 discloses a method for operating an electric drive train for a work machine. Automated braking intervention occurs when an inadmissible acceleration occurs during recuperation operation, for example, when the work machine is supposed to be braked regeneratively, but the braking effect is too low due to the downhill force. The entire disclosure of DE 10 2020 203 594 A1 is incorporated by reference into the present patent application.

[0008] Also known in the art are so-called SAHR brakes. SAHR stands for Spring Applied Hydraulic Released and denotes intrinsically safe brakes that close without pressure and can be used as both auxiliary and parking brakes. The braking effect is achieved by the spring force acting on friction elements that are connected to the ground via the machine's torque train. This functionality can also be achieved with gas-released brakes. In the following, the term SAHR brake is used for both hydraulically and pneumatically released brakes.

[0009] However, the known drive trains for work machines, in particular the known electric drive trains for work machines, are disadvantageous in that when driving down a slope at a comparatively high speed, they are often no longer able to generate a sufficiently large braking torque or recuperation torque to prevent further inadmissible acceleration of the work machine due to the downhill force into a speed range that is inadmissibly high for the work machine.

[0010] It is an object of the invention to propose an improved method for operating a drive train of a work machine.

[0011] This object is achieved according to the invention by the method for operating a drive train of a work machine according to claim 1. Advantageous embodiments and further developments of the invention emerge from the dependent claims.

[0012] The invention relates to a method for operating a drive train of a work machine, wherein the drive train has a drive motor, a service brake and a booster brake, wherein a drive coupling of the drive motor of the drive train with at least one wheel of the work machine exists, so that when driving down a slope a braking torque of the drive motor counteracts a downhill force acting on the work machine, wherein an automated actuation of the booster brake takes place when the work machine is subject to an inadmissible acceleration and wherein the actuation of the booster brake takes place in accordance with a required braking torque.

[0013] According to the invention, a method is provided for operating a drive train of a work machine. The drive train comprises a drive motor that provides drive power for driving the work machine. The drive motor can be assigned exclusively to a traction drive or also to a working drive of the work machine. The drive train further comprises a service brake and a backup brake, wherein the backup brake can, for example, fulfill a parking brake function. Both the service brake and the backup brake are preferably mechanical friction brakes.

[0014] The drive motor of the drive train is drivingly coupled to at least one wheel of the work machine, for example via a gearbox and a releasable clutch, in particular via a multi-plate clutch. The driving coupling between the drive motor and the at least one wheel means that an acceleration torque generated by the drive motor leads to an increase in the speed of the at least one wheel. The increase in speed of the at least one wheel corresponds to the increase in speed of the drive motor, taking into account a transmission ratio between the drive motor and the at least one wheel. Analogously, a braking torque generated by the drive motor leads to a reduction in the speed of the at least one wheel. Conversely, an acceleration torque of the at least one wheel, which may result, for example, from the work machine traveling down a slope, also leads to an increase in the speed of the drive motor.A braking torque generated by at least one wheel, which can result, for example, from the work machine driving up a slope, leads to a corresponding reduction in the speed of the drive motor.

[0015] The auxiliary brake is automatically activated when the working machine is subject to excessive acceleration, for example, due to a downhill descent. The auxiliary brake is activated according to the required braking torque, whereby the required braking torque is advantageously the braking torque required to reduce the speed of the working machine to such an extent that no further excessive acceleration occurs due to the braking torque of the drive motor alone.

[0016] The drive motor generates a braking torque when it is not actively operating and providing torque, but is passively driven by the wheel rotation of the working machine. In an internal combustion engine, the braking torque corresponds to the so-called drag torque; in an electric motor, the braking torque corresponds to the so-called recuperation torque.

[0017] For the purposes of the invention, impermissible acceleration is understood, on the one hand, to mean acceleration not initiated by the driver of the work machine, such as may occur, for example, due to a downhill descent or a downhill force acting on the work machine. On the other hand, impermissible acceleration is also understood to mean an abusive acceleration of the work machine, deliberately initiated by the driver, into a speed range in which drivetrain components could be damaged or even destroyed due to the high speed. Driving at impermissibly high speeds can also lead to safety-relevant or safety-critical driving conditions.

[0018] The impermissible acceleration can be detected, for example, like any other acceleration of the work machine, based on the monitoring and temporal differentiation of a recorded wheel speed, engine speed or other speed in a transmission of the work machine. It is also conceivable that the acceleration is detected, for example, via a satellite navigation system. In particular, however, the mere occurrence of acceleration during recuperation mode of an electric drive motor or during towing mode of the combustion-powered drive motor can be used to conclude that the acceleration is impermissible, since the recuperation mode or towing mode of the drive motor is generally used to decelerate the work machine because the recuperation mode or towing mode inherently provides a braking torque.A simultaneous acceleration thus contrasts with a deceleration initiated by the driver of the working machine or at least the desire to maintain the current speed, which is to be achieved by the recuperation operation or towing operation.

[0019] The method according to the invention is characterized in that the actuation of the auxiliary brake also takes place in accordance with a thermal load on the auxiliary brake and in that the auxiliary brake is designed as a spring-loaded and hydraulically or pneumatically releasable brake.

[0020] This means that when applying the auxiliary brake, not only the required braking torque is taken into account, but also the thermal load on the auxiliary brake. This advantageously allows the use of a spring-loaded and hydraulically or pneumatically released brake as the auxiliary brake, which, due to its design, is not normally suitable for use as a service brake.

[0021] The assist brake is a so-called SAHR brake, for example a disc brake designed as a SAHR brake.

[0022] To advantageously avoid a sudden onset of the braking effect and to achieve a gradual braking effect, e.g., for comfort reasons, a modulation of the applied opening pressure, i.e., the counterforce to the spring elements, is advantageously provided. A preferred option for modulation is electronically controlled proportional valves in the supply line of the SAHR spring-loaded brake. By activating the valve, the pressure can be adjusted almost continuously. For safety reasons, the corresponding valves are preferably open without current.

[0023] The balance between braking deceleration, energy input (heating of the auxiliary brake), frequency and time interval of actuation can be worked out analytically or mathematically or in driving tests and serves as the basis for the actuation of the auxiliary brake.

[0024] Preferably, it is provided that the impermissible acceleration is detected by simultaneously monitoring and relating a setting of a device for specifying the speed of the drive motor and a travel speed of the work machine. The device for specifying the speed can be any control or regulating device for specifying the speed of the drive motor, e.g. an accelerator pedal, a lever or even a rotary actuator. Thus, an impermissible acceleration can be detected solely by comparing information which is available in the work machine without additional sensors. For example, if the travel speed of the work machine increases, which can be detected in particular by a change in wheel speed, a change in engine speed or a change in transmission speed, but at the same time a setting of the device for specifying the speed of the drive motor remains unchanged, ieIf it appears that the driver of the machine clearly does not want any acceleration to occur, then an impermissible acceleration is detected. Impermissible acceleration can also be detected if the setting of the device for specifying the speed of the drive motor is even reduced and the speed of the machine still increases.

[0025] Preferably, provision is made for a gradient to be detected. For this purpose, means for detecting a gradient can be provided. The means for detecting a gradient can, for example, be designed as a satellite navigation system. The satellite navigation system can, for example, be GPS, Galileo or Glonass. The satellite navigation system also comprises a digital memory in which digital map data is stored. This digital map data advantageously comprises topographical data, i.e., altitude information and changes in altitude. Thus, a gradient can also be detected using the satellite navigation system, namely by determining a current position of the work machine and reading out the topographical map data at the determined position of the work machine.

[0026] Alternatively, it is preferably provided that the means for detecting a gradient are designed as fill level sensors of fluid containers of the work machine. Suitable fluid containers of the work machine can be, for example, a possibly provided fuel tank, a cooling water tank, a windshield washer tank, or an expansion tank for hydraulic fluid of a working drive of the work machine. Depending on their specific arrangement in the fluid containers of the work machine, the fill level sensors can thereby detect an inclination of the work machine, and based on the detected inclination of the work machine, it can in turn be recognized that the work machine is on a gradient. For example, it is possible for a fill level sensor in the cooling water tank, which detects the coolant fill level, to detect a supposed increase in the coolant level when the work machine is tilted in the front direction, which corresponds to the work machine traveling down a slope.Conversely, this level sensor would detect a sudden apparent decrease in the cooling water level when the machine is driving uphill.

[0027] According to a preferred embodiment of the invention, the drive motor is designed as an electric motor and, in recuperation mode, provides the braking torque generated by the drive motor. In recuperation mode, the drive motor, designed as an electric motor, provides a braking torque and simultaneously recuperates electrical energy. This enables energy-efficient operation of the drive train.

[0028] Since the braking torque available in recuperation mode is largely determined by the

[0029] speed of the electric motor, whereby the braking torque is comparatively high at low speeds and becomes comparatively low at higher speeds, the actuation of the auxiliary brake must, depending on the value of the impermissible acceleration, reduce the travel speed of the work machine to such an extent that the drive motor is in a speed range in which it can provide sufficient braking torque due to recuperation. This can also lead to a reduction in the travel speed of the work machine below the travel speed that the work machine had before the impermissible acceleration occurred. Advantageously, the auxiliary brake is only actuated until the travel speed of the work machine or the speed of the drive motor has been sufficiently reduced.

[0030] According to a further preferred embodiment of the invention, it is provided that the amount of heat supplied to the auxiliary brake during braking operation is continuously determined and a cumulative counter is increased during actuation, wherein the cumulative counter is reduced again over time if no actuation occurs. The cumulative counter is thus a measure of the amount of heat introduced into the auxiliary brake due to braking operation. It increases as long as the auxiliary brake is actuated and decreases again over time if the auxiliary brake is not actuated. Thus, a measure of the temperature and thus of the continued braking capacity of the auxiliary brake can be determined in a comparatively simple manner solely based on the counter and in particular without temperature measurement.

[0031] By specifying appropriate parameters, the counter takes into account, for example, the mass of the working machine, the applied braking force, and the maximum permissible temperature of the auxiliary brake. The counter also advantageously takes into account the cooling capacity acting on the auxiliary brake, for example, in the form of the quantity and temperature of the cooling oil supplied to the auxiliary brake.

[0032] According to a particularly preferred embodiment of the invention, the cumulative counter is not reduced when the working machine is at a standstill. Since cooling oil is typically not pumped when the working machine is at a standstill, and airflow cannot flow past the auxiliary brake, a comparatively slow cooling process occurs. This cooling process is ignored to simplify the method by not reducing the counter when the working machine is at a standstill.

[0033] Advantageously, the counter can be reset to an initial value, for example the value zero, when the ignition of the working machine is switched off and switched on again after a predeterminable time interval.

[0034] According to a particularly preferred embodiment of the invention, it is provided that a current travel speed of the working machine is continuously recorded and continuously compared with a predeterminable limit speed, wherein when the limit speed is exceeded, the braking torque of the auxiliary brake is adjusted by modulating the hydraulic or pneumatic pressure in such a way that the actuation of the auxiliary brake reduces a travel speed of the working machine to such an extent that no inadmissible acceleration occurs solely due to the braking torque generated by the drive motor.

[0035] In other words, the excessive acceleration will not be automatically counteracted by applying the auxiliary brake as long as the driving speed of the work machine does not exceed the speed limit. Regardless of this, the driver of the work machine naturally retains the option of manually applying the brakes, for example, using the service brake, to prevent excessive acceleration.

[0036] The limiting speed advantageously depends on the respective downhill force acting and thus on the gradient of the slope the machine is traveling down. The greater the downhill force, the greater the braking torque required by the auxiliary brake to maintain or reduce the driving speed of the machine. At the same time, since the braking torque available from the drive motor in recuperation mode is largely determined by the drive motor's speed, with the braking torque being comparatively high at low speeds and becoming comparatively low at higher speeds, the limiting speed is advantageously lower on a comparatively steep slope than on a comparatively flat slope.

[0037] Depending on whether the auxiliary brake is hydraulically or pneumatically actuated, hydraulic or pneumatic actuation is achieved by modulating the auxiliary brake accordingly. This modulation ensures that the braking torque of the auxiliary brake is applied evenly, rather than suddenly. It also allows the braking torque to be controlled to provide a braking torque that is tailored to the braking application required.

[0038] By reducing the driving speed of the work machine to such an extent that excessive acceleration is no longer possible due to recuperation alone, the work machine can continue driving without further braking intervention and thus without brake wear. Furthermore, since the entire braking energy is provided through recuperation, it can be converted almost entirely into electrical energy, which can later be used again to drive the work machine.

[0039] After the working machine has been braked to a travel speed below the limit speed, the auxiliary brake can be opened to cool down.

[0040] According to a further particularly preferred embodiment of the invention, it is provided that a maximum permissible vehicle speed of the work machine is limited and / or the speed threshold is reduced as long as the counter is above a limit value.

[0041] The limit value advantageously indicates the thermal load capacity of the auxiliary brake, i.e. it is an indicator of how much heat can be introduced into the brake during a braking process before it is permanently damaged or at least before the braking properties of the auxiliary brake are temporarily impaired due to the amount of heat introduced.

[0042] By limiting the maximum permissible vehicle speed of the working machine and / or reducing the speed threshold, it can be ensured that the working machine is reliably held in a speed range that does not require any further actuation of the auxiliary brake, solely via the braking torque in recuperation mode of the drive motor.

[0043] According to another particularly preferred embodiment of the invention, the brake application is repeated a first time with a first modified modulation, and a first modified limit value is specified if the vehicle speed is still above the limit speed when the counter reaches the limit value. The first modified modulation can, for example, generate a higher braking torque than the previously used modulation, resulting in a greater reduction in speed and, if necessary, bringing the work machine into a speed range via the first modified modulation in which the work machine can be braked exclusively via the braking torque in recuperation mode of the drive motor.

[0044] If a repeat brake application with a first modified modulation is planned, the counter limit value is advantageously selected so that the auxiliary brake can perform another brake application without thermal damage or even destruction. The first modified counter limit value is accordingly higher than the original limit value.

[0045] According to yet another particularly preferred embodiment of the invention, the brake application is repeated a second time with a second modified modulation, and a second modified limit value is specified if the vehicle speed is still above the limit speed when the counter reaches the first modified limit value. The second modified modulation can, for example, generate an even higher braking torque than the first modified modulation, resulting in an even greater reduction in speed and, if necessary, the second modified modulation can bring the work machine into a speed range in which the work machine can be braked exclusively via the braking torque in recuperation mode of the drive motor.

[0046] If a second repetition of the brake application with a corresponding, second, modified modulation is planned, the first modified limit value of the counter is advantageously selected so that the auxiliary brake can also perform the further brake application without damage or destruction. The second modified limit value of the counter is accordingly higher than the first modified limit value.

[0047] According to a further preferred embodiment of the invention, the actuation of the auxiliary brake is terminated when the cumulative counter reaches the limit value, the first modified limit value, or the second modified limit value and / or a predeterminable time period for actuating the auxiliary brake is exceeded and / or the speed limit is undershot. This ensures, on the one hand, that the auxiliary brake is not destroyed by continued braking and the associated thermal stress. On the other hand, the auxiliary brake is not subjected to unnecessary wear, and the energy recoverable through recuperation is increased by generating the required braking torque exclusively through the recuperation operation of the drive motor.

[0048] According to a further preferred embodiment of the invention, an acoustic and / or visual and / or haptic warning is issued to the driver when the application of the auxiliary brake is terminated without the speed limit being exceeded. This results in the advantage that the driver can be warned if an impermissible acceleration occurs that cannot be compensated by the braking torque of the recuperation mode and the auxiliary brake. To avoid further acceleration, which could potentially lead to a dangerous situation, the driver can then initiate a braking process using the service brake.

[0049] The invention further relates to an electrified drive train for a work machine, wherein the drive train has a drive motor, a service brake and a booster brake, wherein a drive coupling of the drive motor of the drive train to at least one wheel of the work machine exists, so that a braking torque of the drive motor can counteract a slope force acting on the work machine, wherein the drive train is designed to carry out an automated actuation of the booster brake when the work machine is subject to an inadmissible acceleration and wherein the drive train is designed to carry out the actuation of the booster brake in accordance with a required braking torque.

[0050] The drive train according to the invention is characterized in that the drive train is further designed to actuate the auxiliary brake even in accordance with a thermal load on the auxiliary brake and that the auxiliary brake is designed as a spring-loaded and hydraulically or pneumatically releasable brake.

[0051] This results in the advantages already described in connection with the method according to the invention also for the drive train according to the invention.

[0052] According to a further preferred embodiment of the invention, it is provided that the drive train is designed to carry out the method according to the invention.

[0053] Finally, the invention also relates to a work machine comprising a drive train according to the invention.

[0054] The work machine is preferably a wheel loader. However, it can also be a skid-steer loader, telehandler, dumper, excavator, or tractor. The invention is explained below using exemplary embodiments illustrated in the figures.

[0055] It shows:

[0056] Fig. 1 shows, by way of example and in the form of a flow chart, a possible embodiment of the method according to the invention.

[0057] Identical objects, functional units, and comparable components are designated by the same reference symbols throughout the figures. These objects, functional units, and comparable components are identical in terms of their technical features, unless explicitly or implicitly stated otherwise in the description.

[0058] Fig. 1 shows, by way of example and in the form of a flow chart, a possible embodiment of the method according to the invention.

[0059] In method step 100, the ignition of the working machine is activated or switched on via a switch, thus starting the method according to the invention. Parameters describing the working machine, the drive train, and the auxiliary brake are loaded from a read-only memory into the working memory of a computing unit, which executes the method in the form of a software algorithm.

[0060] In the following process step 101, the actual and maximum permissible travel speeds are recorded at times specified by a clock. The maximum permissible travel speed represents a limit speed and is determined by the gradient of the slope the work machine is traveling down.

[0061] If it is detected in step 102 that the actual driving speed has exceeded the limit speed, the auxiliary brake, which is configured as a so-called SAHR brake, is automatically applied. While the auxiliary brake is being automatically applied in step 103, a cumulative counter is incremented with each clock signal according to the clock generator. The counter is thus a measure of the thermal load on the auxiliary brake, whose temperature continually increases with the duration of the auxiliary brake application.

[0062] The heat introduced into the auxiliary brake by actuating the auxiliary brake is gradually absorbed by the transmission oil or radiated into the environment in step 104. This cooling process occurs continuously as long as the driven machine does not fall below a defined minimum speed. The cumulative counter is therefore reduced in a clock-dependent manner as a function of time, whereby the counter cannot become negative. The reduction in the counter due to cooling of the auxiliary brake occurs cumulatively with the increase in the counter due to actuating the auxiliary brake, so that the reduction in the counter and the increase in the counter are offset against each other at the times specified by the clock generator. When the driven machine is at a standstill, however, the cooling times are disproportionately long, which is why the counter is not reduced below the minimum speed.

[0063] In step 105, the application of the auxiliary brake is aborted if the counter has exceeded a limit. Alternatively, the application of the auxiliary brake is aborted in step 106 if the working machine has reached a travel speed below the limit speed.

[0064] If the counter has exceeded a threshold value during the application of the auxiliary brake, the limit speed remains reduced in step 107 until the counter has reached a value due to cooling at which further application of the auxiliary brake is possible.

[0065] If the actual driving speed of the machine at the end of the

[0066] However, if the actuation of the assist brake in step 108 is still above the limit speed, the actuation is not aborted, for example, but repeated with a first changed modulation.

[0067] If this second attempt to reduce the actual driving speed of the working machine is also not sufficient, the auxiliary brake is actuated again in step 109 with a second modified modulation.

[0068] If this third attempt also does not result in the actual travel speed of the working machine being reduced below the limit speed, the actuation of the auxiliary brake is aborted in step 110 and the auxiliary brake is released in order to be able to cool down.

[0069] In the following step 111, a warning is issued to the driver of the work machine and he is asked to check the actual driving speed of the work machine.

[0070] According to a further embodiment not shown in the figures, after the first attempt there is only a second attempt to reduce the actual driving speed of the work machine, but not a third attempt.

[0071] Reference symbol

[0072] Ignition I Operation of the main switch of the working machine

[0073] Recording actual and maximum permissible driving speed

[0074] Driving speed exceeds speed limit automated application of the assist brake

[0075] Cooling of the assist brake

[0076] Counter exceeds limit

[0077] Driving speed below limit speed

[0078] Reduction of the limit speed second attempt to reduce the actual driving speed third attempt to reduce the actual driving speed

[0079] Cooling of the assist brake

[0080] Warning to the driver

Claims

Patent claims 1. A method for operating a drive train of a working machine, wherein the drive train comprises a drive motor, a service brake and an auxiliary brake, wherein there is a drive coupling of the drive motor of the drive train with at least one wheel of the working machine, such that during a descent a braking torque of the drive motor counteracts a downward force acting on the working machine, wherein an automated actuation of the auxiliary brake takes place (103) if the working machine is subject to an impermissible acceleration (102) and wherein the actuation of the auxiliary brake takes place according to a required braking torque (103), characterized in that the actuation of the auxiliary brake also takes place according to a thermal load on the auxiliary brake (107, 111) and that the auxiliary brake is designed as a spring-applied and hydraulically or pneumatically releasable brake.

2. Method according to claim 1, characterized in that the drive motor is designed as an electric motor and provides the braking torque generated by the drive motor in a recuperation mode.

3. Method according to at least one of claims 1 or 2, characterized in that the amount of heat supplied to the support brake during braking operation is continuously determined and a cumulative counter is increased during actuation (103), wherein the cumulative counter is reduced again over time when no actuation takes place (104).

4. Method according to claim 3, characterized in that the cumulative counter is not reduced when the working machine is at a standstill.

5. Method according to at least one of claims 3 to 4, characterized in that a current driving speed of the working machine is continuously recorded and continuously compared against a predefinable The limit speed is compared (101 , 102), whereby if the limit speed is exceeded the braking torque of the support brake is adjusted by modulating the hydraulic or pneumatic pressure (103) such that the actuation of the support brake reduces the driving speed of the working machine to such an extent that no impermissible acceleration occurs solely due to the braking torque generated by the drive motor (106).

6. Method according to at least one of claims 3 to 5, characterized in that a maximum permissible vehicle speed of the working machine is limited and / or the speed threshold is reduced as long as the counter is above a limit value (107).

7. Method according to at least one of claims 1 to 5, characterized in that the brake actuation is repeated for a first time with a first modified modulation and a first modified limit value is specified when the vehicle speed is still above the limit speed when the limit value is reached by the counter (108).

8. Method according to claim 7, characterized in that the brake actuation is repeated a second time with a second modified modulation and a second modified limit value is specified if, when the first modified limit value is reached by the counter, the vehicle speed is still above the limit speed (109).

9. Method according to at least one of claims 1 to 8, characterized in that the actuation of the support brake is terminated when the cumulative counter reaches the limit value, the first modified limit value or the second modified limit value and / or a predefinable time period for the actuation of the support brake has been exceeded (105) and / or the limit speed has been undershot (106).

10. Method according to at least one of claims 1 to 9, characterized in that an acoustic and / or visual and / or haptic warning is issued to the driver when the application of the support brake is terminated without the limit speed having been undercut (111 ).

11. Electrified drive train for a working machine, wherein the drive train comprises a drive motor, a service brake and an auxiliary brake, wherein there is a drive coupling of the drive motor of the drive train with at least one wheel of the working machine, such that a braking torque of the drive motor can counteract a downward force acting on the working machine, wherein the drive train is configured to perform an automated actuation of the auxiliary brake when the working machine is subject to impermissible acceleration and wherein the drive train is configured to perform the actuation of the auxiliary brake according to a required braking torque, characterized in that the drive train is further configured toThe actuation of the support brake should also be carried out according to a thermal load on the support brake, and the support brake should be designed as a spring-loaded brake that can be released hydraulically or pneumatically.

12. Drive train according to claim 11, characterized in that the drive train is configured to perform a method according to at least one of claims 1 to 11.

13. Working machine comprising a drive train according to at least one of claims 11 and 12.

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