WO2018122186A1 - Method and control device for determining a state of a tribological system of a motor vehicle tranmission - Google Patents

Abstract

The invention relates to a method (30) for determining a state of a tribological system (20) of a motor vehicle transmission (14) which has a plurality of gear sets (R1, R2) and/or a wet clutch assembly (K1, K2). The method also includes the steps: providing a mathematical model (32) which reproduces ageing of the tribological system (20) and maps the state of the tribological system (20) onto an ageing variable (38), the mathematical model (32) including a function (36) of an energy input (HEG) into the tribological system (20) over time and, optionally, the temperature, and/or including a function (34) of a metal input (HFEG) into the tribological system (20) over time and, optionally, the temperature; comparing (40) the ageing variable (38) which reproduces the state of the trobological system (20) with an ageing threshold; and outputting a first warning (41) when the ageing variable (38) exceeds the ageing threshold.

Description

 Method and control unit for determining a state of a tribological system of a motor vehicle transmission

The present invention relates to a method for determining a state of a tribological system of a motor vehicle transmission having a plurality of wheelsets and / or a wet-running clutch assembly.

Furthermore, the present invention relates to a control unit for a motor vehicle transmission, wherein the control unit is designed to carry out the determination method of the type described above. Motor vehicle transmissions are generally operated using a fluid, in particular an oil. The fluid is used in particular for the lubrication of wheelsets and bearings of the motor vehicle transmission. In many cases, modern automotive transmissions also include wet-running clutch assemblies. In this case, a fluid of the motor vehicle transmission is further used for lubricating such a clutch arrangement. applies, but in particular also for the cooling during the transmission of torque. Furthermore, the fluid also serves to Reibwertaufbau to transmit torque.

The fluid of the motor vehicle transmission is subject to an aging process. In many cases, it is therefore prescribed that the fluid of the motor vehicle transmission is replaced at prescribed maintenance intervals. The establishment of fixed maintenance intervals, however, has the disadvantage that the maintenance intervals are generally designed for heavy use of the motor vehicle transmission. Such a strong or

Sporting stress of the motor vehicle transmission leads to an earlier aging of the fluid than a gentle use of the motor vehicle transmission.

In many cases, therefore, the fluid is replaced too early. Further it is not

excluded that a maintenance interval under special load may also be too short. However, a strongly aged fluid can also lead to damage to the motor vehicle transmission.

Against the above background, it is known from the document DE 20 209 007 593 U1 to trigger an oil change as needed, namely when a wear limit of the oil is reached. This is to be achieved by a system for the care and / or quality control of oil, the system comprising an oil, a filter arrangement for filtering the oil with at least one microfilter, and a measuring arrangement for determining the state of the oil. The measuring arrangement includes at least one calibratable sensor for detecting at least one parameter of the oil. The microfilter and the sensor are integrated via a secondary line into an oil circuit. The sensor may, for example, be a capacitive sensor.

Document EP 2 169 221 B1 discloses a method for monitoring a transmission of a wind energy plant with a transmission fluid circuit, wherein the number and / or the size and / or the type of particles contained in the transmission fluid is determined by means of at least one particle counter, wherein when at least one first limit value is exceeded by a measured value, a status message is generated and wherein at least a second limit value is exceeded by a measured value, an operating parameter of the wind turbine is changed.

From the document DE 10 2008 019 500 B4 an optical measuring arrangement for detecting physical and / or chemical parameters of a liquid sample is known, wherein the measuring arrangement comprises an infrared light source and a sample container, in which a liquid to be examined is received and in the beam path of the infrared light source is arranged. Furthermore, the measuring arrangement includes a spectral apparatus for selecting and / or masking individual wavelength ranges, and an infrared detector. The thickness of the sample container should be variably adjustable in the direction of the beam path.

From the document DE 102 50 205 B4 a device for viscosity determination is also known, in particular for determining an oil quality in an internal combustion engine. In this case, a sloshing behavior of an engine oil or a transmission oil is detected, preferably by a level sensor. The Schwappverhalten should depend on the viscosity of the oil. With knowledge of mass forces acting on the engine oil, it is possible to infer the viscosity of the engine oil and thus its quality from the fluctuations over time of an oil level.

Against the above background, it is an object of the invention to provide an improved

Specify a method for determining a state of a tribological system and an improved control unit.

The above object is achieved by a method for determining a state of a tribological system of a motor vehicle transmission having a plurality of wheelsets and / or a wet-running clutch assembly, characterized by the steps:

Providing a mathematical model that simulates an aging of the tribological system and that maps the state of the tribological system to an aging variable, the mathematical model of an ne function of an energy input on at least one, preferably different temperature levels in the tribological system over time and / or includes a function of a metal input into the tribological system over time,

Comparing the aging variable, which simulates the state of the tribological system, with an aging threshold, and

- Issuing a first warning if the aging variable exceeds the age threshold.

Further, the above object is achieved by a control device for a motor vehicle transmission, wherein the control device is designed and configured to perform the method according to the invention.

By providing a mathematical model by means of which an aging of the tribological system can be simulated, it is possible to detect an aging of the tribological system without additional hardware. In particular, no special sensors of optical or capacitive type are necessary.

In addition, the mathematical model can be designed so that it is not just a

 The viscosity of a gear oil in the model represents or models, but also other aging aspects, such as an energy input on at least one, preferably different temperature levels and / or a metal entry.

Under a metal entry is in particular an entry of particles to understand that are, for example. Iron-based and are registered in an abrasion of teeth of a meshing of a wheel in the fluid.

The term of the tribological system is generally broad and can the

Include aging state of all components that are within the motor vehicle transmission in a functional relation to the fluid of the motor vehicle transmission. This may in particular be an aging of a wet-running clutch and an aging of the fluid itself. In particular, the inventive method is used to determine a state of a fluid of the motor vehicle transmission, in particular an oil, preferably an ATF oil.

In some powertrains, a wet-running clutch assembly has its own fluid sump, which in particular contains an ATF oil, and the gearbox with the wheelsets includes a further fluid sump, which preferably contains another fluid, in particular hypoid oil.

The method according to the invention can be applied individually to both fluid sumps. In a motor vehicle in which two separate fluid sumps of the type described above are present, two different methods can be carried out, in which case different mathematical models may then be used.

Of particular importance is the aging of the fluid in the present context, however, because the aging of the fluid can affect the function of a wet-running multi-plate clutch. Since the fluid is generally disposed between the fins of such a wet-running clutch assembly, the aging of the fluid also affects the friction behavior of such a clutch. Therefore, it may happen that an aged oil leads to comfort limitations in clutch operations (for example, plucking or the like).

With the method according to the invention, such problems can be avoided since, by applying the mathematical model, a needs-based first warning can be output as to whether an exchange of a fluid of the motor vehicle transmission is soon or immediately indicated.

The first warning is particularly visible on a display in a cockpit of a vehicle and allows the driver to timely approach a workshop for performing a fluid change. Overall, therefore, a need-based fluid change without additional

Messtechnik / Hardware be realized. This results in a piece price optimized solution for motor vehicle transmission. In addition, it is possible to carry out an online evaluation and a detection at the end customer. Maintenance-related and, in particular, customer-dependent fluid changes can result in maintenance costs and maintenance intervals being extended if necessary. There is also a conservation of resources and a reduction in environmental impact, as less oil must be replaced over the service life during maintenance.

Furthermore, consequently, driveability and good comfort result permanently. Furthermore, a good NVH behavior results durably and over the lifetime.

A critical component wear (eg in the wet-running clutch assembly) can be avoided by timely maintenance, in particular a timely fluid change. Depending on the component quality and driver variations, an oil life can be better utilized. If necessary, service costs can be reduced. Unit price increases can be avoided.

The state variables used for operating the mathematical model are preferably variables that are detected in the motor vehicle transmission anyway. This can be in particular a number of revolutions of one wheel set or of several sets of wheels, wherein the number of revolutions can be easily calculated on the basis of the already known speeds of an input shaft and / or an output shaft of the transmission. Furthermore, such state variables, which are in any case measured, may include the wheel set torque transmitted via a wheel set. Since in automated vehicle transmissions, and these are in particular the torque which is provided on the one hand by a drive motor and which on the other hand is transmitted by a transmission input-side clutch arrangement, is already known (eg measured or calculated), In this regard, no additional hardware is required. Another state variable may be the temperature, for example that of the fluid or that of the clutches. Furthermore, further state variables may be a torque transmitted by a clutch of the wet-running clutch arrangement. This too is generally known in automated transmissions. Also, this may be the temperature of such a clutch assembly, which can be detected in particular by an already existing temperature sensor in a drain region of the clutch. In particular, such a sensor measures the temperature of fluid which has passed through the wet-running clutch (in particular from radially inward to radially outward) and which has been heated within the clutch arrangement due to a possibly existing frictional engagement and then flows back into a fluid sump. The temperature measurement can be arranged in particular in front of a fluid cooler, which cools the fluid again before it is passed into the fluid sump. Alternatively, the state variables can also be calculated.

The function of an energy input into the tribological system can be determined in particular by linking a clutch torque and a slip speed.

The function of a metal load in the tribological system can be determined in particular by linking a number of revolutions of a wheel and a torque transmitted from the wheelset.

In the case of the function of the metal input, in a preferred embodiment, a separate summation of such linked values as a function of the temperature may also be carried out, wherein these individual regions are then preferably weighted differently.

In the determination of the energy input can also be a separate summation over the time of links from clutch torque and slip speed for different temperature ranges, these individual summed values are then preferably weighted differently. Due to the different weights, the fact can be taken into account that an energy input at a higher temperature can contribute disproportionately to aging. Accordingly, a metal entry can be disproportionately harmful at high temperature ranges.

The reasons for this may lie in physical and / or chemical properties of the fluid. At higher temperatures, in particular chemical processes can occur between the individual components, in particular processes between the original constituents of the oil and introduced particles.

Overall, an aging of the tribological system can be modeled precisely by the mathematical model, so that a fluid exchange as needed can be realized.

The object is thus completely solved.

According to a particularly preferred embodiment, the mathematical model is plausibilized by various other boundary conditions, which in particular include the mileage of the motor vehicle transmission of the vehicle, in which the motor vehicle transmission is installed.

Thus, according to a preferred embodiment, the method includes the further steps of detecting a mileage of the motor vehicle transmission and / or a vehicle in which the motor vehicle transmission is installed, comparing the detected mileage with a first mileage threshold and issuing a second warning, if the recorded mileage exceeds the first mileage threshold.

In particular, the first mileage threshold may be such a threshold that corresponds to a regularly scheduled maintenance interval. For example, this may be a value that is greater than 120,000 km, in particular greater than 150,000 km. The first mileage threshold is preferably less than 250,000 km, in particular less than 200,000 km.

Upon issuance of the second warning, in turn, an indication may be made in a cockpit of the vehicle to alert the driver that a fluid change is indicated.

According to a further preferred embodiment, the method according to the invention comprises the further steps of detecting a mileage of the motor vehicle transmission and / or a vehicle in which the motor vehicle transmission is installed, the recorded mileage with a second mileage threshold is preferably smaller than the first mileage Threshold and / or compare and suppress the first warning when the detected mileage falls below the second mileage threshold.

In this type of plausibility check, it is found that, due to the mileage determined, aging of the fluid can not have progressed so far that a fluid change is necessary. The second mileage threshold is preferably less than the first mileage threshold and / or is preferably in a range between 80,000 km and 150,000 km. Consequently, if the mileage is less than such a mileage threshold, no first warning is issued, even if the mathematical model pretends that an aging threshold has already been exceeded.

For example, the aging threshold and / or the first mileage threshold and / or the second mileage threshold may be calculated, for example, from an individual driving profile. The aging threshold value and / or the first mileage threshold value and / or the second mileage threshold value may, for example, take into account the individual driving profile and / or torques at certain rotational speeds and / or power inputs over a mileage, for example a milage, and / or Aging variables are calculated. Particularly preferably, the first mileage threshold and / or the second mileage threshold is calculated taking into account the aging threshold and / or the aging variable.

A further plausibility check can be carried out by analyzing characteristic oscillations of a shaft of the motor vehicle transmission.

It is therefore of particular advantage, if the method includes the further steps of detecting a shaft speed of a shaft of the motor vehicle transmission, to analyze the detected shaft speed for characteristic vibrations, wherein upon detection of characteristic vibrations, a vibration value is increased and / or wherein the aging variable Function of the vibration value and / or the vibration analysis is.

If a fluid of a transmission, in particular of an automated transmission that includes a wet-running clutch, has aged, this can lead to characteristic vibrations in the region of the input shaft of the transmission. Such characteristic oscillations may be, for example, in a frequency range between 5 Hz and 50 Hz, in particular in a frequency range from 5 Hz to 15 Hz.

If vibrations are detected on the shaft, which are in this frequency range and preferably additionally a predetermined vibration value, z. B. amplitude value is exceeded, it is concluded that characteristic oscillations exist that indicate in particular an advanced age of the fluid, so in particular occur due to an increased age of the fluid.

As a result, a frequency of oscillation value exceeding can be detected, which is incremented each time such vibrations are detected. From a certain frequency can be concluded that the fluid has reached a certain degree of aging. This can be incorporated into the aging variable. Furthermore, the vibration value and / or its frequency of occurrence can be used for plausibility of the aging variable of the mathematical model, so that the aging variable is a function of the vibration value and / or the vibration analysis itself.

According to a further preferred embodiment, in conjunction with the

 The preamble of claim 1 is a separate invention, the method includes the steps:

Detecting whether, during operation of the motor vehicle transmission, a first gearset is engaged for transmitting power,

Detecting a first number of revolutions of the first gearset and detecting a first gearset torque transmitted from the first gearset,

Linking the first number of revolutions and the first set of wheels torque to a first load value,

- summing the first load value over time to a first load value sum, and

Determining the state of the tribological system as a function of the first load value sum value.

The first load value sum value represents at least partially a metal entry into the tribological system over time.

It is preferred if the method has the further steps:

Detecting whether at least one second wheel set is engaged during operation of the motor vehicle transmission, Detecting a second number of revolutions of the second set of wheels and detecting a second set of wheelset transmitted by the second set of wheels,

Linking the second number of revolutions and the second pair of wheelset torque to a second value of load,

- summing the second load value over time to a second load value sum, and

- Determining the state of the tribological system as a function of the first load value sum value and the second load value sum value.

The second meshing wheel set may be a wheel set that, like the first set of wheels, is currently used to transmit torque, or a wheel set that is not currently used to transmit torque.

In general, it is possible to determine a load value sum value for each Radsatzeingriff.

In general, it is then possible to weight the load value sum values differently, depending on whether torque is transmitted via the respective wheelsets or not.

According to a further preferred embodiment, the first load value and / or the second load value is linked to a wheelset temperature.

The wheelset temperature may be, for example, a sump oil temperature and / or a gearing mass temperature and / or a clutch temperature. The sump oil temperature and / or the gearing mass temperature and / or the clutch temperature can be detected, for example, by means of at least one sensor become. Alternatively, the sump oil temperature and / or the gearing mass temperature and / or the clutch temperature may be calculated.

The intermeshing mass temperature may in particular be a

Gear energy of a gear pair act. The toothing mass temperature can be calculated, for example, from variables to be detected. Preferably, at least one torque value and / or at least one rotational speed and / or at least one temperature can be included in the calculation of the gearing mass temperature.

The coupling temperature may preferably be a temperature at the wet-running clutch arrangement.

Alternatively or additionally, the first load value and / or the second

Load value can be linked to at least one other temperature at another characteristic point of the motor vehicle transmission.

Consequently, a weighting may also be made as to whether or not to add up

Load value at a low or high temperature was determined (especially within different temperature ranges) was determined.

The different load value sum values can then be weighted differently depending on the respective temperature range, wherein it is preferred if load value sum values, which were determined at a high temperature, are weighted more heavily, thus allowing the fluid to age faster in the model.

According to a further preferred embodiment, the first gearset torque and / or the second gearset torque is arranged in one of at least two Radsatzdrehmomentbereichen, wherein the first Radsatzdrehmoment and / or the second Radsatzdrehmomentoment depending on the classification with a different power in the first and in the second Debit value received. In this way, it is possible to let the load value and the load sum value enter into the aging process with a different power depending on the size of the wheel set torque.

In other words, it is assumed that higher Radsatzdrehmomente received with a higher power, so for example. Square or cubic in the load sum value, whereas low Radsatzdrehmomente received only slightly (or not) in the respective load value.

According to a further preferred embodiment, which in conjunction with the

 The preamble of claim 1 represents a separate invention, the method further comprises the steps:

Detecting whether, during operation of the motor vehicle transmission, a clutch of the wet-running clutch arrangement transmits a clutch torque,

Detecting a slip speed of the clutch,

Coupling the clutch torque with the slip speed to an energy input value, in particular to a clutch energy input value,

Adding up the energy input value, in particular the clutch energy input value, over the time to an energy input sum value, and

Determining the state of the tribological system as a function of the energy input sum value, in particular as a function of the first load value sum value and / or of the second load value sum value. The energy input is preferably classified and / or weighted according to coupling temperatures or coupling temperature ranges. The energy input sum value reflects the energy input usable in the mathematical model for mapping aging of the tribological system.

In this case, a clutch torque and a slip speed are linked together. This linkage, as well as the other links above, may in particular be multiplications.

Furthermore, these links can generally be normalized.

The coupling temperature is preferably a temperature which is determined by detecting or calculating a fluid temperature after the fluid has cooled the coupling, ie in particular before flowing back into a fluid sump and / or before passing the fluid into a fluid cooler.

According to a further preferred embodiment, at least two different energy input sum values for different temperature ranges of the clutch temperature over time are summed up and combined to form an energy input total sum value.

This makes it possible to weight the transmission of clutch powers within higher temperatures more than the same coupling powers at lower temperatures.

The sum values mentioned above can also be referred to as damage values. In order to determine an aging variable or a total damage value, it is possible to combine one or more load sum values and one or more energy input sum values, in particular to add them to one another. By applying the individual summation values with coefficients, the

 different contributions of the sum values to a total damage value or an aging variable, respectively.

It is understood that the above and the following still apply

 explanatory features are usable not only in the combination given, but also in other combinations or alone, without departing from the scope of the present invention.

Embodiments of the invention are illustrated in the drawings and will be explained in more detail in the following description. Show it:

Fig. 1 is a schematic representation of a drive train for a motor vehicle

 including a tribological system;

FIG. 2 shows a schematic representation of a method for determining a state of a tribological system of a motor vehicle transmission of a drive train; FIG.

3 shows a schematic representation of a method for determining a state of a tribological system as a function of a load value sum value; and

4 shows a schematic representation of a method for determining a state of a tribological system as a function of an energy input sum value.

A drive train for a motor vehicle is shown schematically in FIG. 1 and designated generally by 10. The drive train 10 has a drive motor 12, such as, for example, an internal combustion engine, an electric motor or a hybrid drive unit. The drive motor 12 provides at its output a drive speed n _VM , as well as a drive torque TQ _VM - The output of the drive motor 12 is connected to an input of a dual-clutch transmission 14. An output of the dual-clutch transmission 14 is connected to a differential 16, by means of which drive power is distributed to driven wheels 18L, 18R.

The dual-clutch transmission has a dual-clutch arrangement with a first

Clutch K1 and a second clutch K2. The clutches K1, K2 are connected on the input side to the output of the drive motor 12 or ZMS (dual-mass flywheel). An output of the first clutch K1 is connected to an input shaft of a first subtransmission TG1. An output of the second clutch K2 is connected to an input shaft of a second subtransmission TG2. One of the partial transmissions TG1, TG 2 is assigned to the odd forward gears, the other partial transmissions to the straight forward gears. The input shaft of the first subtransmission TG1 rotates at a speed n _M and provides a torque TQ _M at the input of the subtransmission TG1. In a corresponding manner, the input shaft of the second partial transmission TG 2 rotates at a speed n _β and provides a torque TQ _!

Further, it is shown in Fig. 1 that the first clutch K1 transmits a torque TQ «i. Accordingly, the second clutch K2 transmits a torque TQ «2

The clutches K1, K2 are designed as wet-running multi-disc clutches and, like the partial transmissions TG1, TG2, are part of a tribological system 20. The tribological system 20 in the present case includes a single fluid 22 in the form of a transmission oil, for example an ATF oil , The fluid 22 is received in a fluid sump 24. The fluid sump has a temperature T _s .

By means of the fluid, the clutches K1, K2 are lubricated during operation and cooled. In Fig. 1 it is indicated that a fluid flowing through the clutch K1 fluid after cooling the clutch K1 has a temperature T «i, which corresponds to the temperature of the clutch. Correspondingly, the clutch K2 has a temperature T _K2 corresponding to the temperature of the fluid used to use the clutch K2. The partial transmissions TG1, TG 2 have wheels R1, R2. In Fig. 1, a wheelset R1 and for the partial transmission TG2 a set of wheels R2 are schematically indicated for the partial transmission TG1. In practice, however, these partial transmissions usually each have several sets of wheels, corresponding to the number of gear stages. As a rule, the partial transmissions TG1, TG2 are accommodated in a common housing, which forms the fluid sump 24. A fluid sump of a clutch housing may be formed separately therefrom, but may also be fed from the same fluid sump 24.

In Fig. 1 is additionally shown that the driven wheels have a speed n _A e. This drive speed is used to represent a speed of the motor vehicle and to display a mileage. The speed n _AB can be measured by means of an odometer odo.

Fig. 1 also shows a control unit 26, which may be formed in particular as a transmission control unit.

The control unit 26 is configured to automatically actuate the dual-clutch transmission 14, that is to open and close the clutches K1, K2 as required and to engage and disengage gear stages in the partial transmissions TG1, TG2 as required. Furthermore, the control unit 26 preferably also controls the tribological system 20, thus providing, if necessary, fluid 22 for the clutches K1, K2, and / or for the wheel sets R1, R2.

The fluid 22 undergoes aging during operation of the drive train 10. Aging can be due to physical and / or chemical phenomena. Partially the chemical property of the fluid changes. Partially particles are introduced into the fluid, for example due to a metallic abrasion within the partial transmission.

In the present case, a method is provided to exchange the fluid as needed, ie, when a fluid change is indicated, since the fluid can no longer safely or comfortably fulfill its tasks, or anticipated, after a certain mileage could no longer meet. Such a method is shown schematically in FIG. 2 and designated by 30.

The method 30 is based on a mathematical model 32 that simulates aging of the tribological system 20. The mathematical model 32 includes a function or method 34 for detecting a metal load in the fluid. The method or the function 34 leads to a load value sum value or damage value H _FE . The mathematical model 32 further includes a method or function 36 for determining an energy input into the tribological system 20. Damage caused by the energy input into the tribological system 20 is mapped to an energy input sum H _E.

The damage values H _FE and H _E , which are provided by the functions 34, 36, are values which accumulate during operation of the drive train 10 or its tribological system 20, that is to say quasi represent current state values for the tribological system 20 ,

The mathematical model 32 maps the state of the tribological system 20 to an aging variable 38. The aging variable 38 may be a single variable, but may also be formed by a set of variables.

In a comparison step 40, the aging variable 38 is compared with an aging threshold, not shown. If the aging variable falls below the aging threshold, the method returns to the mathematical model 32. However, if the aging variable 38 exceeds the aging threshold, a first alert 41 is output, which may be displayed on a display 42 in the cockpit of a motor vehicle, for example the drive train 10 is installed. The first warning 41 indicates to a driver of the motor vehicle that a fluid change is to be carried out soon, for example within a certain time or within a certain mileage frame, that is to say up to a certain mileage. The mathematical model 32 determines how much the tribological system 20 is damaged during the service life of the drive train 10. At high loads can be done within the same mileage of a motor vehicle, a significantly higher damage to the fluid than at low stress. Accordingly, in a stressful driving style, for example, a fluid change is displayed earlier than in a defensive driving style. Likewise, the driving profile, for example. Towns, out of town, highway and mountains, and environmental conditions, eg. Outside temperature can be considered. Furthermore, component scattering, for example, varying iron input, clutch friction package scattering or oil batch scattering can be taken into account.

In order to make the mathematical model and its aging variable 38 plausible, it is preferable if a number of further steps are carried out in the context of the method 30.

On the one hand, by means of an odometer odoeters a mileage detection, which indicates the mileage 46 of the drive train 10 and the motor vehicle, in which the drive train 10 is installed.

The mileage 46 is compared in a comparison step 48 with a first mileage threshold D _HIGH . The first mileage threshold D _H I _GH corresponds to a value above which a fluid change is indicated in each case, regardless of the type of load during driving. The value of D _HIG H can, for example, be in a range of 150,000 km to 250,000 km. If the mileage 46 is below the mileage threshold D _HIGH , no further action takes place. However, if the mileage 46 exceeds the mileage threshold D _HIGH , a second warning 49 is output, which is also displayed on the display 42.

The second warning may be identical in content to the first warning, but may also be an escalation level higher, so for example. Impose an immediate oil change within a short period or a short mileage, otherwise the driveability of the vehicle uncomfortable or the transmission hardware are pre-damaged can. Further, the mileage 46 is compared with a second mileage threshold D _LO w, in a comparison step 50. The second mileage threshold D _L ow is a value below which a fluid change is not necessary. The comparison step 50 is an optional step, for which reason the corresponding lines are shown in dashed lines in FIG. 2; the connection between 40 and 42 is then preferably interrupted (not shown).

The comparison step 50 is preferably performed after the comparison step 40 has revealed that the aging variable 38 has exceeded the aging threshold. In this case, the comparison step 50 queries whether the actual mileage 46 is below the second mileage threshold value. If this is the case, a warning suppression occurs via 52, so that the first warning 41 is not output. However, if the second mileage threshold D _L ow is exceeded, the first warning 41 is output unchanged.

The value of D _LO w can be, for example, in a range of 80,000 km to 150,000 km.

FIG. 2 further shows that at least the rotational speed ni of an input shaft of a

Part of the transmission is detected, in a detection step 56. The detected speed ni is analyzed in an analysis section 58. If the detected speed signal includes vibrations that are within a predetermined frequency range and / or exceed a predetermined amplitude, characteristic vibrations are detected. These, in combination with the mathematical model, indicate that the fluid 22 (part of tribological system 20) has aged, since such characteristic vibrations typically only occur after many hours of operation (eg> 500h-2000h) when the fluid has aged , The analysis section 58 includes a frequency analysis 62, for example in the form of a

Bandpass filter. The bandpass filter may, for example, pass a frequency range of 5 Hz to 20 Hz and block other frequencies. Typical characteristic frequencies indicative of the state of aging of a fluid are within a range of the natural frequency of the powertrain (eg 5 Hz to 12 Hz). On the other hand, an amplitude analysis 64 queries whether the detected frequencies in the particular frequency band transmitted by the frequency analysis 62 are above a certain level. If this is not the case, the query usually returns and no further action is triggered. However, when the amplitudes are above a certain threshold value, a vibration value J is incremented in an incrementing step 60.

The occurrence of characteristic vibrations can, for example, for plausibility of the

 Comparative step 40 are used, as indicated by a circle / dot symbol. Also the vibration value, which is increased more and more over the mileage, can be such a plausibility criterion.

In other words, if the comparison step 40 shows that one of the

 mathematical model 32 provided aging variable 38 has exceeded an aging threshold, but the analysis of the rotational speed ni has shown that no characteristic oscillations occur, possibly the first warning 41 can also be suppressed.

Fig. 3 shows in schematic form an example of a method 34 for determining a

 Metal input into a fluid of a tribological system 20 of a motor vehicle transmission 14th

Under this procedure, 34 the number of rollovers and the number of revolutions are recorded for a set of wheels R1, first, as shown at N _R1. On the other hand, the torque TQ _R1 transmitted by the wheel set _{R1 is} detected.

In general, it is possible to link the number of revolutions N _R1 and the wheelset torque TQ _R1 with one another, as indicated schematically at 70 in FIG. Subsequently, such a linked value is summed over time, as indicated at 71. Subsequently, such a summed value can still be weighted or weighted with a constant. This eventually leads to a current value of HFEG of a metal feed into the tribological system 20 over time. In the present case, after the detection of the wheel-locking torque TQ _R1 , however, first in a comparison step 68 it is queried whether the current torque lies in a first wheelset torque range TQ _RB i or in a second, different wheelset torque range TQ _RB2 . The second Radsatzdrehmomentbereich TQ _RB2 is associated with higher torque than the first Radsatzdrehmomentbereich TQ _RB i. The detected torque TQ _R1 is, if it is in the first Radsatzdrehmomentbereich TQ _RB1 , with a first power P, applied, which may be 1, for example, so that in a linking step, the detected torque TQ _R i linked unchanged with the number of revolutions N _R1 becomes. The linked value or the load value determined in this way is subsequently determined in a step 71 _! summed up, resulting in a load value sum value 72Ί, which is possibly still applied with a constant C _RB i (weighted).

If the wheelset torque TQ _{R1 is} in the second Radsatzdrehmomentbereich TQ _RB2 , the Radsatzdrehmoment TQ _{R1 is applied} to a second power P ₂ , which is higher than Ρ and which may be, for example. 2 or 3, so that the increased torque bspw is square or cubic in the subsequent link 70 ₂ received. The wheel set torque TQ _R i applied to the second power P ₂ is linked to the number of revolutions NRI in the linking step 70 ₂ to form another load value, which is then summed up or integrated in a summation step 71 ₂ , to a load value sum value 72 ₂ . This further load value sum value 72 ₂ may also be subjected to a constant C _RB2 (weighted). The steps 70 _x to 72 _x can be multiplied as desired to introduce further classes via further P _x and TQ _RBx .

The load value sum values 72i, 72 ₂ , 72 _x are linked in a further linking step 73 to a first metal load value H _FE i. This can be converted directly to the total metal input value H _F EG.

Alternatively, a link between the number of revolutions and Radsatzmoment for more

Set of wheels, as shown schematically in Fig. 3 for a second set of wheels R2, where the function leads to a second metal input value H _F E2, with the first metal input value H _FE i can be combined to the total metal input value H _FE G.

[00112] The links 70 _! , 70 ₂ , 72 _x are preferably multiplications. The link

 73 and the further linking are preferably additions.

The function of the metal input into the tribological system over time is

 In particular, characterized in that a number of revolutions N and a torque are linked together and the link value over time is summed or integrated. As a result, it can be determined in the mathematical model how high the load of the wheel set and thus a possible abrasion and metal entry or iron entry into the fluid was or is.

[001 14] In Fig. 3 at 74, or 74 ₂ indicated that in the load value, resulting from the

Links 70 ^ and 70 ₂ results in each case can also enter a temperature of the fluid, which is in particular represented by a fluid sump temperature T _s .

[001 15] The temperature can enter into the load value with a simple power, that is, directly, but can also enter into the respective load value differently depending on a temperature range.

[001 16] The model of FIG. 3 can also be used if a motor vehicle transmission does not have a wet-running clutch arrangement. In this case, the mathematical model alone can focus on how the metal entry into the fluid was, in order to be able to account for the aging of the fluid.

[001 17] Conversely, in vehicles in which, for example, a wet-running multi-disc clutch arrangement of a motor vehicle transmission has its own transmission budget independent of the wheel sets, the method of FIG. 3 is dispensed with. In this case, the mathematical model 32 illustrated in FIG. 2 merely relies on the energy input, as described below with respect to FIG. 4. In many transmissions, however, it is preferred if the aging variable is evaluated both due to the metal input and due to the energy input.

FIG. 4 shows in schematic form a method or function 36 of an energy input H _EG in the tribological system 20 of a motor vehicle transmission over time.

4 shows that the coupling torque TQ _K1 transmitted by the clutch is detected for a clutch K1, as is the clutch temperature T _K i of the clutch, which can be derived, for example, from the temperature of the fluid after it has flowed through the clutch , Alternatively, a fluid sump temperature T _s can also be used.

In general, the method 36 is based on that the coupling temperature T _K i and the

Coupling torque TQ ₁ are linked together, to an energy input value, which is then summed or integrated.

In the present case, it is also determined in a query step 78 whether the clutch temperature

I is in a first clutch temperature range T _K BI or in a second, different clutch temperature range T << B2. The second clutch temperature range T _K B2 relates to higher temperatures than the first clutch temperature range T << BI -

When the clutch temperature T i falls within the first clutch temperature range T << BI, the clutch temperature T _K i is unchanged linked to the clutch torque TQ _K i in a step 80-i. The energy input value determined in this way is summated or integrated in a step 81 ₁ , so that an energy input sum value 82 _{1 is} determined. This can be applied (weighted), for example, with a constant C _K BI, or a different function, for example, a power can be added.

When the clutch temperature T "i falls within the second clutch temperature range T" B2, the clutch temperature T _K i is unchanged or, as in FIG. 3, with a higher power, ie, for example, square or cubic, in a linkage step 80 ₂ linked to the clutch torque TQ «i. The energy input value resulting therefrom is summed up or integrated in a step 81 ₂ so that a second energy input sum value 82 ₂ . The second energy input sum value 82 ₂ can likewise be applied (weighted) to a constant C _K B2, for example, before it is linked to the first energy input sum value 82 in a linking step 84, specifically to a first energy input damage value H _E «I.

In order to meet the different temperature ranges, for example, the

 Constant C «B2 be significantly higher than the constant C« BI, so that the higher temperature is weighted accordingly different. This can be done alternatively or in addition to an application with different powers.

Conversely, in the method of FIG. 3, a weighting instead of or in addition to the powers Pi, P _{2 can} also be effected by different constants C _RB i, C _RB2 .

The method described in FIG. 4 for the clutch K1 for determining the

Energy input damage value H _E «i can be performed in parallel for the second clutch K2, as is schematically indicated in FIG. 4, so that a second energy input damage _value H _EK2 results, which is associated with the first energy input damage value H _E KI is added to the total energy input damage value HEG-

[00128] The total metal load value H _F EG and the total energy input damage value

H _EG can be combined with each other to the aging variable 38, for example by summation.

Claims

claims 1 . Method (30) for determining a state of a tribological system (20) of a motor vehicle transmission (14) which has a plurality of wheelsets (R1, R2) and / or a wet-running clutch arrangement (K1, K2), characterized by the steps: Providing a mathematical model (32) simulating an aging of the trivial system (20) and mapping the state of the tribological system (20) to an aging variable (38), the mathematical model (32) having a function (36 ) an energy input (HEG) at least one temperature level into the tribological system (20) over time and / or a function (34) of a metal input (H _FEG ) into the tribological system (20) over time, Comparing (40) the aging variable (38) that mimics the state of the tribological system (20) with an aging threshold, and - issuing a first warning (41) when the aging variable (38) exceeds the age threshold. 2. The method of claim 1, further comprising the steps, a mileage (46) of the motor vehicle transmission (14) and / or a vehicle, in which the motor vehicle transmission (14) is installed, the detected mileage (46) with a first running power threshold (D _H IGH) to compare output (49) (48) and a second warning when the detected mileage (46) exceeds the first power threshold overflow (D _H IGH). 3. The method of claim 1 or 2, comprising the further steps, a mileage (46) of the motor vehicle transmission (14) and / or a vehicle, in which the motor vehicle transmission (14) is installed to record the recorded mileage (46) Compare a second mileage threshold (D _L ow) and the first warning (41) to suppress (52) when the detected mileage (46) falls below the second mileage threshold (D _LO w). 4. The method according to any one of claims 1-3, wherein the aging threshold and / or the first mileage threshold (D _H IGH) and / or the second mileage threshold (D _L ow) are calculated. 5. The method according to any one of claims 1-4, with the further steps, a  Shaft speed (n of a shaft of the motor vehicle transmission (14) to detect the detected shaft speed (ni) to analyze characteristic oscillations (62, 64), wherein upon detection of characteristic vibrations, a vibration value (J) is increased and / or wherein the aging variable ( 38) is a function of the vibration value (J) and / or the vibration analysis (62, 64). 6. The method according to any one of claims 1-5 or according to the preamble of  Claim 1, with the steps: Detecting whether, during operation of the motor vehicle transmission (14), a first wheel set (R1) is engaged for transmitting power, Detecting a first number (N _R1 ) of revolutions of the first set of wheels (R1) and detecting a first set of wheelset torque (TQ _R ) transmitted by the first set of wheels (R1), Combining (70,) the first number of revolutions (N _R1 ) and the first set of wheels torque (TQRI) AT a first load value, Summing (71 *,) the first load value over time to a first load value sum value (72 ^, and - Determining the state of the tribological system as a function of the first load value sum value (72T). 7. The method of claim 6, comprising the steps of: Detecting whether at least one second wheel set (R2) is engaged during operation of the motor vehicle transmission (14), Detecting a second number (N _R2 ) of revolutions of the second set of wheels (R2) and detecting a second set of wheelset torque (TQ _R2 ) transmitted by the second set of wheels ( _R2 ), - linking the second number of revolutions (N _R2 ) and the second set of wheels torque (TQ _R2 ) to a second load value, - summing the second load value over time to a second load value sum value (72 ₂ ), and Determining the state of the tribological system (20) as a function of the first load value sum value (72,) and the second load value sum value (72 ₂ ). 8. The method of claim 6 or 7, wherein the first and / or the second load value with a wheelset temperature (T _s ) is linked. 9. The method according to claim 8, wherein the wheelset temperature (T _s ) is a sump oil temperature and / or a gearing mass temperature and / or a clutch temperature. 10. The method of claim 9, wherein the toothing mass temperature is calculated. 11. The method of claim 6, wherein the first gearset torque (TQ _R1 ) and / or the second gearset torque is classified into one of at least two gearset torque ranges (TQ _RB i, TQ _RB2 ) and wherein the first gearset torque (TQ _R1 ) and / or the second Radsatzdrehmoment depending on the classification with a different power (P ₀ , P ₂ ) is received in the first and in the second load value. 12. The method according to any one of claims 1 - 1 1 or according to the preamble of  Claim 1, with the steps: Detecting whether, during operation of the motor vehicle transmission (14), a clutch of the wet-running clutch arrangement (K1, _K2 ) transmits a clutch torque (TQK _I , TQ _K2 ), Detecting a slip speed of the clutch, - Coupling (80) of the clutch torque (TQ «i, TQ« ₂ ) with the  Slip speed to an energy input value, - summing the energy input value over time to an energy input sum value (82), and - Determining the state of the tribological system (20) as a function of the energy input sum value (82). 13. The method of claim 12, wherein at least two different energy input sum values (82 _! , 82 ₂ ) for different temperature ranges (T _K BI, T _KB2 ) of the clutch temperature (T _<< i, T _K2 ) over time are summed up and to a Energy Entry Totals are summarized. 14. Control unit (26) for a motor vehicle transmission (14), wherein the control unit (26) is designed and configured to perform the method according to one of claims 1 to 13.