DE102021203202A1 - Method for operating a drive train of a work machine, drive train for a work machine and work machine - Google Patents

Abstract

The invention relates to a method for operating a drive train (10) of a working machine (20), the drive train (10) comprising at least one electric motor (11, 31, 41), the at least one electric motor (11, 31, 41) having a theoretical Service life is assigned, with an actual service life of the at least one electric motor (11, 31, 41) depending on a temperature (T) profile of the at least one electric motor (11, 31, 41) over the actual service life, with the temperature (T ) is detected (100) and the power of the at least one electric motor (11, 31, 41) is limited (107) if the temperature (T) of the at least one electric motor (11, 31, 41) exceeds a limit temperature (Tlimit) ( 101, 102), so that the actual service life does not fall short of the theoretical service life. The method according to the invention is characterized in that the theoretical service life includes at least one defined time window (twindow) within which the temperature (T) of the at least one electric motor (11, 31, 41) can exceed the limit temperature (Tlimit) without the Power limitation takes place. The invention also relates to a corresponding drive train (10) and a working machine (20).

Description

The present invention relates to a method for operating a drive train of a work machine according to the preamble of claim 1, a drive train for a work machine according to the preamble of claim 12 and a corresponding work machine.

Electrically driven work machines, such as wheel loaders, skid steer loaders, telehandlers, dumpers or even excavators, are known in the prior art. Such electrically driven working machines are either purely electrically driven, i.e. they only have an electric battery or an electric accumulator for their energy supply, or they are diesel-electrically driven, which means that the required energy is provided by a diesel-driven generator, usually in Connection to an electrical buffer storage, such as an appropriately sized capacitor, is provided. In all cases, the mechanical power required for the travel drive and the working drive is provided by one or more electric motors. Furthermore, hybrid-electric working machines are also known in which the mechanical power required for operation is primarily provided by an internal combustion engine, usually a diesel engine. An additionally provided electric motor is fed by a battery or an accumulator and typically assumes a so-called boost function here.

In this context, describes the DE 20 2014 000 738 U1 a wheel loader driven purely by an electric motor, which has a first electric motor for a traction drive and a second electric motor for a working drive.

Furthermore, it is known that the electric motors provided for the travel drive and the working drive can overheat in certain situations and in particular during prolonged operation. In order to protect the electric motors from being destroyed by overheating, so-called derating takes place when a definable temperature threshold is exceeded, i.e. the electrical power consumption of the electric motor is limited to such an extent that the electric motor can cool down again or at least no further heating takes place.

The as yet unreleased DE 10 2020 211 422.6 the applicant describes, for example, a mathematical model for operating an electric drive of a machine, in which, taking into account an inertial torque of the electric motor, a torque to be applied by the electric motor in the immediate future for a speed change is determined using a mathematical model. In this way, an impending overheating can be detected at an early stage and the overheating can also be counteracted at an early stage.

However, the known methods for operating an electric drive train of a working machine have the disadvantage that when a previously defined limit temperature of an electric motor is reached - possibly after a previously performed, gradual derating - they completely switch off the electric motor in order to prevent further heating in any case impede. As a result, work to be performed by the working machine cannot be continued and an undesirable delay in the work progress occurs.

It is an object of the invention to propose an improved method for operating a drive train of a working machine.

According to the invention, this object is achieved by the method for operating a drive train of a work machine according to claim 1 . Advantageous refinements and developments of the invention emerge from the dependent claims.

The invention relates to a method for operating a drive train of a work machine, the drive train comprising at least one electric motor, a theoretical service life being assigned to the at least one electric motor, with an actual service life of the at least one electric motor depending on a temperature profile of the at least one electric motor over is the actual service life, the temperature being detected and the power of the at least one electric motor being limited if the temperature of the at least one electric motor exceeds a limit temperature, so that the actual service life does not fall below the theoretical service life. The method according to the invention is characterized in that the theoretical service life includes at least one defined time window within which the temperature of the at least one electric motor can exceed the limit temperature without the power being limited.

The invention thus describes a method which relates to the operation of a drive train of a working machine, the drive train having at least one electric motor. Provision is also preferably made for the drive train to consist of two drives that can be operated independently of one another, namely a working drive and a travel drive. Each of these two drives, the working drive as well as the driving drive drove, is advantageously each assigned its own electric motor, namely an electric traction motor or an electric working motor.

The drive train is therefore advantageously designed as an electric drive train.

The traction drive is driven by the traction motor according to a power requirement of the traction drive, and the working drive is driven by the working engine according to a power requirement of the working drive. A power requirement is generally understood to mean a control input for the travel drive or for the working drive, for example a desired acceleration of the travel speed or a desired lifting of a loaded shovel. Such a control input has the consequence that the respectively addressed drive, ie the traction drive or the working drive, has to provide the mechanical power required to convert the control input via the traction motor or the working motor. For this reason, in almost all situations, a control input is linked to a corresponding performance requirement. It is irrelevant whether the power request is made by an operator of the working machine, e.g. by actuating an accelerator pedal or a work joystick, or by an automated control intervention of an assistance system of the working machine or the assistance system. Since the working motor and the traction motor naturally each have efficiencies below 100%, they can heat up during operation in accordance with the performance requirements. In the case of a power limitation that then takes place, the supply of electrical energy to the traction motor or the working motor is now limited, contrary to the respective power requirement, to such an extent that the traction motor or the working motor can reduce its temperature again.

A theoretical service life is assigned to the at least one electric motor, the theoretical service life being determined using a temperature-dependent service life model. Data is used in the service life model that usually comes from laboratory tests and calculations on a reference electric motor of the same construction. The reference electric motor is usually subjected to a temperature that is significantly above its intended operating temperature in order to cause faster aging and increased wear of the reference electric motor. As a result, the entire service life of the reference electric motor can be run through comparatively quickly. Based on the measured total service life and the known influence of temperature on the actual service life, the theoretical service life of all identical electric motors can be determined for a specific maximum operating temperature. The theoretical service life is often used in the form of a guarantee, e.g. to give a buyer of the at least one electric motor certainty as to how long the at least one electric motor can be used. In this respect, the theoretical service life also represents an economic criterion for the selection of an electric motor intended for a specific purpose.

The service life model is a mathematical model that describes a mathematical relationship between a thermal load on the at least one electric motor and its theoretically expected service life. The thermal load is described here via the temperature of the at least one electric motor. The higher the temperature, the greater the reduction in the theoretically expected service life. Conversely, a low temperature during operation of the at least one electric motor leads only to a slight reduction in the service life that can theoretically be expected. Such lifetime models are known per se in the prior art.

Provision is particularly preferably made for the theoretical service life to be determined by using the limit temperature in the temperature-dependent service life model. It follows from this that the at least one electric motor just reaches the theoretical service life if it were operated constantly at the limit temperature throughout its actual service life. The actual service life can of course only be determined when the at least one electric motor has reached the end of its service life.

Ultimately, however, the actual service life of the at least one electric motor is dependent on the course of the temperature of the at least one electric motor over its actual service life. If the at least one electric motor is operated at low temperatures, its actual service life is correspondingly reduced more slowly than the theoretical service life. However, if it is operated at higher temperatures, its actual service life will shorten correspondingly faster than the theoretical service life. So that the theoretical service life is actually achieved, so that the actual service life is at least as long as the theoretical service life, a limit temperature is advantageously specified, which the at least one electric motor generally must not exceed during its service life. This limit temperature is usually selected in such a way that the at least one electric motor just reaches the theoretical service life if it were operated constantly at the limit temperature throughout its actual service life. The actual service life can of course only be determined when the at least one electric motor has reached the end of its service life.

In order to be able to be sure that the at least one electric motor is not operated above the limit temperature and its actual service life is thus reduced to such an extent that the theoretical service life can no longer be achieved, the temperature is recorded constantly or regularly. It is not absolutely necessary for the temperature profile to be recorded over the actual service life, but it is conceivable. If it is detected that the limit temperature has been exceeded, the power of the at least one electric motor is limited, for example in the form of a reduction in electric current applied to the at least one electric motor, so that it can be ensured that the actual service life of the at least an electric motor does not fall below the theoretical service life and the at least one electric motor does not fail before the theoretical service life is reached. As a result of this limitation of the electrical power supplied, the at least one electric motor can cool down to such an extent that it again reaches a temperature below the limit temperature.

At the same time as the power is limited, the cooling measures with which the at least one electric motor is cooled can advantageously also be intensified. The temperature of the at least one electric motor can thus be reduced even more quickly, so that it again reaches a temperature below the limit temperature correspondingly more quickly and is operational again.

The respective temperature is measured directly, for example, by a temperature sensor that is in physical contact with a housing of the working motor or the traction motor. For example, the temperature of the stator can easily be measured through direct contact. However, a temperature measurement on the stator or on the coil windings of the at least one electric motor is also conceivable, which can be carried out without contact using infrared measurements, for example. Non-contact temperature detection is particularly preferred for the temperature detection of the rotor. Finally, it is also conceivable to determine the temperature of the at least one electric motor purely by calculation based on a known applied voltage, a known current consumption and known motor characteristics.

Both the temperature of the traction motor and the temperature of the working motor are preferably recorded.

The power limitation can, for example, be a power limitation by a fixed value by which the maximum permissible power is limited, for example 20%, 30%, 50%, 75% or even 100%, with a power limitation of 100% of the at least one electric motor temporarily shut down completely until the temperature falls below the limit.

According to the invention, it is now provided that the theoretical service life includes at least one defined time window within which the temperature of the at least one electric motor can exceed the limit temperature without the power being limited. Advantageously, it is additionally provided that the temperature of the at least one electric motor can exceed the limit temperature within the at least one defined time window without the actual service life falling below the theoretical service life. This means that in this case the theoretical service life is not determined solely on the basis of the limit temperature, but rather that at least one defined time window within which the limit temperature can be exceeded is provided during the theoretical service life. In other words, the theoretical service life is calculated in such a way that the limit temperature may be exceeded during operation of the at least one electric motor during the at least one defined time window, since the excess was taken into account from the outset when determining the theoretical service life. Therefore, exceeding the at least one defined time window cannot lead to a temperature-related faster reduction of the actual service life compared to the theoretical service life.

This results in the advantage that the drive train or the work machine can be operated at least temporarily, namely during the at least one defined time window, in load ranges that would otherwise not be possible. In particular, power peaks that are requested for a comparatively short time can thus be implemented without the work to be performed having to be interrupted due to an impending overheating or an overheating of the at least one electric motor that has already occurred. Thus, for example, driving uphill at high speed without reducing performance be executed limitation, which would require an interruption without executing the method according to the invention or could only be continued at reduced speed. Likewise, for example, operation of the working drive for a specific period of time at high power can be continued comparatively longer as long as the at least one defined time window has not yet been fully exhausted. This increases the usefulness of the drive train, since activities performed by the work machine do not have to be interrupted or continued with reduced performance.

The invention makes use of the knowledge that operating states of the drive train or the at least one electric motor in which the temperature of the at least one electric motor exceeds the limit temperature occur comparatively rarely, but then lead to an undesirable delay in the continuation of the work to be performed to lead. Since such operating states are now firmly planned into the theoretical service life over a certain period of time, namely the at least one defined time window, they can also be permitted within the at least one defined time window without a failure of the at least one electric motor occurring within the - in the theoretical service life guaranteed by the manufacturer.

The at least one time window is at least one time window that is available once during the actual service life of the at least one electric motor. After the temperature of the at least one electric motor was above the limit temperature for the duration of the at least one time window, the time window is closed. The next time the limit temperature is exceeded, the power of the at least one electric motor is therefore limited.

Irrespective of this suspension of the power limitation, a critical temperature is advantageously provided, which, if exceeded, nevertheless results in a power limitation. The critical temperature is preferably noticeably above the limit temperature and describes a temperature which, when reached, immediately threatens irreversible damage to at least one electric motor or other components of the drive train. In order to prevent the critical temperature from being reached at all, a power limitation or a stepwise increasing power limitation can already take place, for example, in the temperature range between the limit temperature and the critical temperature.

According to a preferred embodiment of the invention, it is provided that the theoretical service life includes a large number of defined time windows, each defined time window being assigned to an individual temperature range above the limit temperature. In this way, different high temperature ranges above the limit temperature can be taken into account accordingly.

According to a particular embodiment of the invention, it is provided that the time windows from the multiplicity of defined time windows become shorter as the distance from the limit temperature increases. This results in a pyramid-shaped step model from different time windows, which together represent the multiplicity of time windows, with the lowest and largest or time-longest step being assigned to a comparatively lowest temperature range lying directly above the limit temperature. Alternatively, a lowest level can also be below the limit temperature. The next higher level is assigned to the next higher temperature range and is already smaller or shorter than the lowest level. The subsequent stage is associated with an even higher temperature range and is again shorter than the previous stage. This model can be continued and include any number of stages or time windows. This results in the advantage that different high temperature ranges above the limit temperature can not only be distinguished, but also different lengths of time can also be allowed, which in particular takes into account the wear, which usually increases exponentially with the temperature.

According to a further preferred embodiment of the invention, it is provided that the at least one time window can be divided into a large number of time segments which can be spaced apart in time and result in the at least one time window in total. This means that the at least one time window does not have to be used contiguously as long as the total duration of the temperature in the respectively assigned temperature range above the limit temperature over the actual service life of the at least one electric motor is not longer than the at least one defined time window in total. For example, the temperature of the at least one electric motor in a defined time window of 1 hour over the actual service life of the at least one electric motor can be 20 minutes, then 10 minutes and finally another 30 minutes above the limit temperature, without the actual service life being compared to the theoretical service life would be shortened.

According to a further preferred embodiment of the invention, it is provided that the power is limited when the temperature of the at least one electric motor exceeds the limit temperature and the at least one defined time window has already closed. Since in this case the permissible operating time of the at least one electric motor above the limit temperature has already completely expired, ie the at least one defined time window has already closed, the power is now limited in order to prevent the actual service life from being reduced below the theoretical service life.

If a large number of defined time windows are provided, the power is advantageously always limited when the temperature of the at least one electric motor is associated with a defined time window that has already closed.

According to a particularly preferred embodiment of the invention, it is provided that in a large number of defined time windows, time segments of a defined time window assigned to a higher temperature range are used for operation of the at least one electric motor in a defined time window assigned to a lower temperature range if the time window assigned to the lower temperature range defined time window is already closed. This means that the at least one electric motor can still be operated in a specific temperature range above the limit temperature if the defined time window assigned to this temperature range has already closed and at the same time at least one other time window assigned to an even higher temperature range has not yet closed is. In this case, the defined time window assigned to the higher temperature range can be used instead of the already closed defined time window assigned to the corresponding temperature range, so that a corresponding time segment of the defined time window assigned to the higher temperature range is used up. This results in greater flexibility in the operation of the at least one electric motor above the limit temperature. In particular, power restrictions that would slow down the work of the drive train or the working machine can be avoided.

According to a particularly preferred embodiment of the invention, it is provided that the time segments of the time window assigned to a higher temperature range are lengthened by a definable factor if they are used for the operation of the at least one electric motor in the time window assigned to a lower temperature range. The factor advantageously takes into account the fact that the at least one electric motor experiences greater wear in a higher temperature range than in a lower temperature range. Accordingly, the at least one electric motor can be operated in a correspondingly lower temperature range for a correspondingly longer time than in a correspondingly higher temperature range, without it experiencing greater wear. In this way, the available operating time above the limit temperature can be used very flexibly and performance restrictions can be largely avoided.

The factor can, for example, be fixed, for example with a value of 1.5, or can be specified as a function of the temperature ranges involved in each case.

According to a further preferred embodiment of the invention, it is provided that the power limitation takes place in stages or continuously. This results in the advantage that a flexible reaction to an observed increase in temperature of the at least one electric motor is possible. For example, in addition to the limit temperature, other temperature limits can be defined, exceeding which leads to a gradually increasing power limitation. Or the power limitation follows a continuous and differentiable function, for example a straight line, which continuously increases the power limitation as the temperature rises above a definable limit temperature, until the at least one electric motor is finally shut down completely.

In this way, in particular, an abrupt reduction in the power of the at least one electric motor to zero can be avoided.

The invention also relates to a drive train for a working machine, the drive train comprising at least one electric motor, with the at least one electric motor being assigned a theoretical service life, with an actual service life of the at least one electric motor depending on a temperature profile of the at least one electric motor over the actual Service life is, wherein the drive train is designed to detect the course via temperature detection means and wherein the drive train is designed to limit the power of the at least one electric motor when a temperature of the at least one electric motor exceeds a limit temperature. The drive train according to the invention is characterized in that the drive train is designed such that the theoretical service life includes at least one defined time window within which the temperature of the at least one electric motor can exceed the limit temperature without the power being limited.

The drive train according to the invention thus enables the method according to the invention to be carried out, which leads to the advantages already described in connection with the method according to the invention.

According to a preferred embodiment of the invention, it is provided that the drive train comprises a working drive and a traction drive, with the traction drive being able to be driven by an electric traction motor in accordance with a power requirement of the traction drive, and with the working drive being drivable by an electric working motor in accordance with a power requirement of the working drive is.

The drive train preferably also includes an electronic control unit or control unit for the travel drive and an electronic control unit or control unit for the working drive. As an alternative, the drive train can also preferably include a common electronic control unit or control unit for the travel drive and the working drive. The control unit or regulating unit for the travel drive creates the power requirement of the travel drive for each situation according to an input from an operator of the working machine or according to an assistance system or a safety system. Likewise, the control unit or regulating unit of the working drive creates the power requirement of the working drive. Alternatively, the performance requirements of the travel drive and the working drive are created by the common control unit or regulating unit.

According to a further preferred embodiment of the invention, it is provided that the temperature detection means are designed to detect the temperature of the working engine and the temperature of the traction motor, each on a coil winding.

The temperature detection means can be embodied as thermoelectric temperature sensors with evaluation electronics or as contactless measuring infrared measuring means. Alternatively or in addition to the plausibility check of the measured temperatures, the temperature detection means can also be embodied as software means that can be executed on an electronic arithmetic unit, such as a microcontroller, which calculates the temperature of the at least one electric motor on the basis of a voltage application, a current consumption and known motor characteristics.

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 for the traction motor and for the working motor independently of one another.

The invention further relates to a working machine, comprising a drive train according to the invention. This also results in the advantages already described in connection with the drive train according to the invention for the work machine according to the invention.

Provision is preferably made for the work machine to be in the form of a wheel loader, dumper, excavator, telehandler, municipal vehicle, garbage truck, mining vehicle, skid steer loader, aircraft tractor or tractor.

The invention is explained below by way of example using the embodiments shown in the figures.

• 1 beispielhaft eine mögliche Ausführungsform eines erfindungsgemäßen Verfahrens zum Betreiben eines Antriebsstrangs einer Arbeitsmaschine in Form eines Flussdiagramms,
• 2 beispielhaft einen Verlauf einer Temperatur über die Zeit im Betrieb eines Elektromotors eines erfindungsgemäßen Antriebsstrang,
• 3 beispielhaft und schematisch eine mögliche Ausbildungsform einer erfindungsgemäßen Arbeitsmaschine und
• 4 beispielhaft und schematisch eine Vielzahl von definierten Zeitfenstern.

Show it:

• 1 an example of a possible embodiment of a method according to the invention for operating a drive train of a working machine in the form of a flowchart,
• 2 for example a course of a temperature over time during operation of an electric motor of a drive train according to the invention,
• 3 exemplary and schematic of a possible embodiment of a working machine according to the invention and
• 4 a large number of defined time windows by way of example and diagrammatically.

Identical objects, functional units and comparable components are denoted by the same reference symbols across the figures. These objects, functional units and comparable components are designed to be identical in terms of their technical features, unless the description explicitly or implicitly states otherwise.

1 shows an example of a possible embodiment of a method according to the invention for operating a drive train 10 of a work machine 20 in the form of a flowchart. The drive train 10 includes at least one electric motor 11, one under laboratory conditions partially experimentally and partially mathematically determined theoretical service life. The theoretical service life indicates the service life that the at least one electric motor 11 is expected to achieve if it were operated constantly at a limit temperature T _limit , the limit temperature T _limit being, for example, the maximum permissible operating temperature during operation of the at least one electric motor 11. The theoretical service life thus generally differs from the actual service life, which can only be determined at the end of the service life of the at least one electric motor 11 . The actual service life of the at least one electric motor 11 is decisively characterized by the course of a temperature T of the at least one electric motor 11 over the actual service life. For example, the theoretical service life includes five defined time windows within which the temperature T of the at least one electric motor 11 can exceed the limit temperature T _limit without the actual service life being reduced any further than the theoretical service life.

The execution of the method according to the invention now begins in step 100 with the detection of the temperature T of the at least one electric motor 11. The temperature T is continuously detected and compared in step 101 with a predefined limit temperature _Tlimit . According to the example, the limit temperature T _limit is 200° C. and is measured on a coil winding of the at least one electric motor 11 . Steps 100 and 101 are repeated constantly. If the comparison in step 101 shows that the detected temperature T has exceeded the limit temperature T _limit , a check is carried out in the following step 102 in which of several temperature ranges ΔT ₁ , ΔT ₂ , ΔT ₃ , ΔT ₄ and ΔT ₅ are above the limit temperature T _limit the detected temperature T of the at least one electric motor 11 is. According to the example, five temperature ranges ΔT ₁ , ΔT ₂ , ΔT ₃ , ΔT ₄ and ΔT ₅ above the limit temperature T _limit are provided, of which the first ΔT ₁ includes the temperatures T from 200° C. to 210° C., the second ΔT ₂ the temperatures T from 210 °C to 220 °C, the third ΔT ₃ the temperatures T from 220 °C to 230 °C, the fourth ΔT ₄ the temperatures T from 230 °C to 240 °C and the fifth ΔT ₅ finally the temperatures T from 240 °C to 250 °C. At the same time, in step 102, a temperature range ΔT ₁ , ΔT ₂ , ΔT ₃ , ΔT ₄ and ΔT ₅ corresponding to the recorded temperature T is selected. In step 103 which now follows, it is checked whether a defined time window t _window assigned to this temperature range ΔT ₁ , ΔT ₂ , ΔT ₃ , ΔT ₄ and ΔT ₅ is still open or is already closed. According to the example, this is the first temperature range ΔT ₁ . If the defined time window t _window,1 assigned to this temperature range is still open, the method is continued in step 104 . A timer is started which measures the operating time of at least one electric motor 11 in this temperature range ΔT ₁ and constantly checks whether the defined time window t _window,1 associated with the temperature range ΔT ₁ is still open or is closing. If the assigned, defined time window t _window,1 is closing or is already closed, a transition is made from method step 103 to step 105 . In step 105 it is checked whether a defined time window t _window, 2 assigned to a higher temperature range ΔT ₂ has not yet closed and can be used for the operation of the at least one electric motor 11 . According to the example, the defined time window t _window,2 assigned to the second temperature range ΔT ₂ is already closed, but the defined time window t _window, 3 assigned to the third temperature range ΔT ₃ is still open. Accordingly, in step 106 the defined time window t _window, 3 assigned to the third temperature range ΔT ₃ is used to operate the at least one electric motor 11 in the first temperature range ΔT ₁ . Here, too, a timer is started again in order to check that the defined time window t _window,3 associated with the third temperature range ΔT ₁ is closing. If the defined time window t _window,3 assigned to the third temperature range ΔT ₁ also closes and a defined time window t _window,4 and t _window, 5 assigned to a higher temperature range ΔT ₄ and ΔT ₅ is no longer available, step 103 proceeds to step 107 passed. The transition from step 103 to step 107 also takes place if a defined time window t _window is no longer available from the outset. In step 107, the power of the at least one electric motor 11 is limited to, for example, 50% of the maximum permissible electrical power. If the temperature T of the at least one electric motor 11 falls below the limit temperature T _limit again as a result of the power restriction, the method is carried out again starting from step 100 .

2 shows an example of a profile 30 of a temperature T _over time t during operation of an electric motor 11 of a drive train ₁₀ according to the invention. At time t ₁ , cooling measures for electric motor 11 are increased so that it no longer heats up and temperature T of electric motor 11 remains constant up to time t ₂ . From time t ₂ , however, electric motor 11 is subjected to a higher power requirement, so that its temperature T continues to rise and at time t ₃ exceeds limit temperature T _limit . According to the example, a check is then carried out to determine whether a defined time window t _window is still open which corresponds to the observed temperature range ΔT ₁ , ΔT ₂ , ΔT ₃ , ΔT ₄ and ΔT ₅ . Since this is the case according to the example, a power limitation of the electric motor 11 that would otherwise occur is therefore suspended. According to the example, the defined time window t _window covers a time span of 30 minutes in total, although 28 minutes of the 30 minutes have already been used up in the past, so that currently only 2 minutes of the defined time window t _{window are} available for operation of the electric motor 11 above the Limit temperature T _limit are available.

In such a defined time window t _window , the electric motor 11 is now operated up to the point in time t ₅ . Already at time t ₄ the temperature T does not rise any further and remains at a constant value above the limit temperature T _limit . The one-time, defined time window t _window ends at time t ₅ , since the remaining 2 minutes have also elapsed. Accordingly, the power of the electric motor 11 is also limited at time t ₅ , so that it can cool down and at time t ₆ it reaches a temperature T below the limit temperature T _limit .

3 shows a possible embodiment of a work machine 20 according to the invention by way of example and schematically. The work machine 20 is designed, for example, as a wheel loader 20 and comprises a drive train 10 according to the invention. The drive train 10 in turn comprises a working drive 30 with an electric working motor 31 and a shovel arm 33 with a shovel 34 working device 32 and a travel drive 40 with an electric travel motor 41, a travel gear 42, a clutch 43 drivingly arranged between the travel motor 41 and the travel gear 42, and driven vehicle wheels 44. The travel motor 41 and the working motor 31 each have a control unit 45, 35 assigned, which controls the traction motor 41 or the working motor 31 and executes the method according to the invention. The control units 45 and 35 are, for example, three-phase inverter modules 45, 35. In addition, both the working motor 31 and the traction motor 41 are each assigned a temperature measuring device 36, 46, with the temperature measuring devices 36, 46 being designed as infrared sensors 36, 46, for example are, which detect the temperature T at the coil windings of the working motor 31 and the traction motor 41, respectively. Furthermore, the drive train 10 also includes an electrical energy store 12. The work machine 20 is designed to carry out the method according to the invention.

4 shows, by way of example and diagrammatically, a large number of defined time windows t _window, for example five defined time windows t _{window 1} , t _{window 2} , t _{window 3} , t _{window 4} and t window ₅ . The five time windows time window t _window,1 , t _window,2 , t _window,3 , t _{window, 4} and t _{window, 5} are five different, adjacent temperature ranges ΔT ₁ , ΔT ₂ , ΔT ₃ , ΔT ₄ and ΔT ₅ assigned, all of which are above the limit temperature T _limit . As can be seen, the defined time windows time window t _window,1 , t _window,2 , t _window,3 , t _window,4 and t _window,5 become shorter in time as the distance from the limit temperature T _limit increases. The result is therefore the pyramid-shaped step model 4 from different defined time windows time window t _window,1 , t _window , ₂ , t _window,3 , t _window,4 and t _window,5 . As can be seen, the lowest and largest or temporally longest stage is associated with a comparatively lowest temperature range _{ΔT 1} lying directly above the limit temperature T limit . This corresponds to the defined time window t _window,1 . The next higher level t _window,2 is assigned to the next higher temperature range ΔT ₂ and is already smaller or shorter than the lowest level. The subsequent stage t _window,3 is assigned to an even higher temperature range and is again shorter than the preceding stage t _window,2 . The stages t _{window 4} and t _{window 5} , which each represent a defined time window t _window , follow at higher temperatures T and thus with increasing thermal distance from the limit temperature T _limit . These levels are assigned according to the temperature ranges ΔT ₄ and ΔT ₅ .

Reference List

10

powertrain

11

electric motor

12

electrical energy storage

20

work machine

30

working drive

31

electric working motor

32

working device

33

shovel arm

34

shovel

35

Control unit, three-phase inverter module

36

Temperature sensing means, infrared sensor

40

traction drive

41

electric traction motor

42

driving gear

43

coupling

44

vehicle wheels

45

Control unit, three-phase inverter module

46

Temperature sensing means, infrared sensor

100

detecting the temperature

101

Comparison of temperature with limit temperature

102

Check in which of several temperature ranges above the limit temperature the recorded temperature lies

103

Check whether a defined time window assigned to a temperature range is still open

104

Start a timer

105

Check whether a defined time window assigned to a higher temperature range is still open

106

Using the defined time window assigned to the third temperature range

107

Power limitation of the at least one electric motor

T

temperature

limit

limit temperature

ΔT1, ΔT2, ΔT3, ΔT4, ΔT5

temperature range

t

time

t1, t2, t3, t4, t5, t6

times

twindow, twindow, 1, twindow, 2, twindow, 3, twindow, 4, twindow, 5

defined time window

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 202014000738 U1 [0003]
• DE 102020211422 [0005]

Claims (16)

Method for operating a drive train (10) of a working machine (20), wherein the drive train (10) comprises at least one electric motor (11, 31, 41), wherein a theoretical service life is assigned to the at least one electric motor (11, 31, 41), wherein an actual service life of the at least one electric motor (11, 31, 41) depends on a temperature (T) profile of the at least one electric motor (11, 31, 41) over the actual service life, the temperature (T) being recorded ( 100) and wherein the power of the at least one electric motor (11, 31, 41) is limited (107) if the temperature (T) of the at least one electric motor (11, 31, 41) exceeds a limit temperature (T _limit ) (101, 102 ), so that the actual service life does not fall below the theoretical service life, characterized in that the theoretical service life includes at least one defined time window (t _window ) within which the temperature (T) of the m at least one electric motor (11, 31, 41) can exceed the limit temperature (T _limit ) without the power being limited. procedure after claim 1 , characterized in that within the at least one defined time window (t _window ) the temperature (T) of the at least one electric motor (11, 31, 41) can exceed the limit temperature (T _limit ) without the actual service life falling below the theoretical service life. Process according to at least one of Claims 1 and 2 , characterized in that the theoretical service life comprises a large number of defined time windows (t window, t _window,1 , t _window,2 , t _window,3 , t _window,4 , t _window,5 ), each defined time window (t _window , t _window,1 , t _window,2 , t _window,3 , t _window,4 , t _window,5 ) an individual temperature range (ΔT ₁ , ΔT ₂ , ΔT ₃ , ΔT ₄ , ΔT ₅ ) above the limit temperature (T _limit ) is assigned. procedure after claim 3 , characterized in that the time windows (t _window , t _{window 1} , t _{window 2} , t _{window 3} , t _{window 4} , t _{window 5} ) from the plurality of defined time windows (t _window , t _{window 1} , t _window,2 , t _{window, 3} , t _window,4 , t _window,5 ) become shorter with increasing distance from the limit temperature (T _limit ). Process according to at least one of Claims 1 until 4 , characterized in that the at least one time window (t _window ) can be divided into a large number of time segments which can be spaced apart in time and result in the at least one time window (t _window ) in total. Process according to at least one of Claims 1 until 5 , characterized in that the power is limited (107) when the temperature (T) of the at least one electric motor (11, 31, 41) exceeds the limit temperature (T _limit ) and the at least one defined time window (t _window ) is already closed. procedure after claim 6 , characterized in that with a large number of defined time windows (t _window , t _{window 1} , t _{window 2} , t _{window 3} , t _{window 4} , t _{window 5} ) time sections of a higher temperature range (ΔT ₁ , ΔT ₂ , ΔT ₃ , ΔT ₄ , ΔT ₅ ) associated defined time window (t _window, t _{window 1} , t _{window 2} , t _{window 3} , t _{window 4} , t _{window 5} ) for operation of the at least one electric motor ((11, 31, 41) in a defined time window (t _window, t _window,1 , t _window,2 , t _window,3 ) assigned to a lower temperature range (ΔT ₁ , ΔT ₂ , ΔT ₃ , ΔT ₄ , ΔT ₅ ). , t _window,4 , t _window,5 ) can be used if the defined time window assigned to the lower temperature range (t _window, t _window,1 , t _window,2 , t _window,3 , t _{window, 4} , t _{window, 5} ) is already closed (105). procedure after claim 7 , characterized in that the time segments of a higher temperature range (ΔT ₁ , ΔT ₂ , ΔT ₃ , ΔT ₄ , ΔT ₅ ) associated time window (t _window, t _window,1 , t _window,2 , t _window,3 , t _{window ,4} , t _window,5 ) can be lengthened by a predeterminable factor if they are used to operate the at least one electric motor (11, 31, 41) in a lower temperature range (ΔT ₁ , ΔT ₂ , ΔT ₃ , ΔT ₄ , ΔT ₅ ) assigned time window (t _window, t _window,1 , t _window,2 , t _{window, 3} , t _{window, 4} , t _window,5 ) can be used. Process according to at least one of Claims 1 until 8th , characterized in that the theoretical service life is determined using a temperature-dependent service life model. procedure after claim 9 , characterized in that the theoretical service life is determined by using the limit temperature (T _limit ) in the temperature-dependent service life model. Process according to at least one of Claims 1 until 10 , characterized in that the power is limited in stages or continuously. Drive train (10) for a working machine (20), wherein the drive train (10) comprises at least one electric motor (11, 31, 41), wherein the at least one electric motor (11, 31, 41) is assigned a theoretical service life, with an actual lifespan of the mind at least one electric motor (11, 31, 41) is dependent on a temperature (T) profile of the at least one electric motor (11, 31, 41) over the actual service life, with the drive train (10) being designed to use temperature detection means (36 , 46) to record the course and wherein the drive train (10) is designed to limit the power of the at least one electric motor (11, 31, 41) when a temperature (T) of the at least one electric motor (11, 31, 41) exceeds a limit temperature (T _limit ), characterized in that the drive train (10) is designed such that the theoretical service life includes at least one defined time window (t _window ) within which the temperature (T) of the at least one electric motor (11, 31, 41) can exceed the limit temperature (T _limit ) without the power being limited. Drive train (1)0 after claim 12 , characterized in that the drive train (10) comprises a working drive (30) and a traction drive (40), wherein the traction drive (40) can be driven by an electric traction motor (41) in accordance with a power requirement of the traction drive (40) and wherein the Working drive (30) can be driven by an electric working motor (31) in accordance with a power requirement of the working drive (30). Drive train (10) according to at least one of Claims 12 and 13 , characterized in that the temperature detection means (36, 46) are designed to detect the temperature (T) of the at least one electric motor (11, 31, 41) in each case on a coil winding. Drive train (10) according to at least one of Claims 12 until 14 , characterized in that the drive train (10) is designed to a method according to at least one of Claims 1 until 9 for the traction motor (41) and/or for the working motor (31) to be carried out independently of one another. Working machine (20), comprising a drive train (10) according to at least one of Claims 12 until 15 .

Images