System and method for monitoring the condition of a wheel of a rail vehicle

Description

[0001] The invention relates to a system and a method for monitoring the condition of a wheel of a rail vehicle, in particular during operation of the rail vehicle.

[0002] During braking, the wheels of a rail vehicle are subjected to severe stress. It is important to prevent damage to the wheels, for example, due to excessive friction or sudden and massive heating of the material. This is particularly difficult when very harsh braking occurs in conditions with unfavorable adhesion properties of the surface. This can occur more frequently, for example, in regions exposed to a maritime climate, especially with high humidity and the associated poor adhesion between wheel and rail.

[0003] Systems are known that prevent a wheel from locking or slipping during braking. This prevents, for example, the formation of flat spots in the otherwise circular circumference of the wheel. However, under adverse conditions, cases can occur in which the wheel is damaged or the material undergoes adverse changes, for example, associated with the formation of martensite in the wheel material. Areas of a metal wheel, particularly in the area of ​​the wheel tread, where the material structure has changed to martensite are harder and more brittle than the surrounding material and are therefore often starting points for the formation of surface cracks and material loss.

[0004] It is known to examine impellers at regular intervals using a non-destructive test and, if necessary, to remove damaged material, for example using a lathe.

[0005] For example, EP 3 517 927 A1 discloses a method for detecting a crack in a wheelset of a rail vehicle.

[0006] Furthermore, DE 198 33 027 C1 describes a method for testing a railway wheel.

[0007] Furthermore, EP 1 485 704 A1 discloses a device for electromagnetic and ultrasonic diagnosis of wheels.

[0008] In addition, EP 3 206 933 A1 describes a method for diagnosing the condition of wheels on rail vehicles.

[0009] From the state of the art, the documents US 2020 / 079343 A1, EP 0 818 372 B1 and CN 111 791 916 A are also worth highlighting.

[0010] It is the object of the present invention to advantageously further develop a system and a method of the type mentioned at the outset, in particular to the extent that the formation of critical structures in the material of a wheel and / or an initiation of cracks can be detected.

[0011] This object is achieved according to the invention by a system for monitoring the condition of a wheel of a rail vehicle.

[0012] According to this, a system for monitoring the condition of a wheel of a rail vehicle is provided, comprising a detection unit configured to detect at least one operating parameter for the wheel in the event of a braking event, an evaluation unit configured to determine a temperature value for the wheel on the basis of the detected operating parameter, and a control unit configured to generate and output an output depending on the determined temperature value.

[0013] The invention is based on the fundamental idea of ​​detecting a structural change in the wheel during operation through temperature or thermal monitoring. The structural diagrams are generally known and can be stored in the system. If thermal monitoring, possibly also through the temporal temperature profile (i.e., monitoring the temperature curve) and the corresponding comparison, or through monitoring the temperature curve alone without comparison, detects that a problematic structural transformation is taking place, could take place, or is to be feared, a corresponding warning message is issued.

[0014] This advantageously provides relevant parameters for the condition and safety of a wheel, as well as for its maintenance. Furthermore, maintenance costs can be optimized by using particularly complex processes in a targeted manner. Furthermore, maintenance work can be advantageously planned and performed as needed rather than at fixed intervals, thus avoiding unnecessary maintenance work. Furthermore, the wheel can be treated on the lathe before cracks in the material can form and spread.

[0015] The condition of the wheel can be monitored, especially during ongoing operation of the rail vehicle. This is an important difference from conventional methods, where monitoring takes place at predetermined intervals, for example, and the rail vehicle must be taken to a workshop. With the invention, the data recorded during braking is evaluated directly, and conclusions about the condition of the wheel can be drawn directly.

[0016] The invention can therefore perform monitoring or diagnostics to detect the formation of martensite and / or other indications of cracks or fractures. Furthermore, it can detect the risk of material weakening. Furthermore, the diagnostics can be used to detect the occurrence of post-braking hazards due to an adverse adhesion profile.

[0017] A fundamental idea of ​​the invention is to determine the probability of martensite formation in the rail vehicle wheel. This information is then used to determine whether an inspection of the wheel, for example using a non-destructive testing method, is indicated and / or whether treatment of the wheel, for example using a lathe, is necessary.

[0018] This takes advantage of the fact that modern rail vehicles often record a variety of parameters that can be used to determine the energy generated at the wheel-rail contact point. In particular, the system utilizes the ability to record the wheel speeds and the speed of the rail vehicle, i.e., a reference speed. These values ​​are already being used, for example, to detect or prevent wheel slippage. For example, a "wheel slide protection"-System (WSP) or a similar system. In addition, a brake control (English: "brake control unit", BCU) recorded values ​​can be used, which record, for example, the brake pressures applied by brake cylinders.

[0019] The speeds of the wheels and the vehicle, as well as the cylinder pressures of the braking system, can be used in a simplified thermal model of the wheel tread material, particularly to determine the temperature distribution within the material. Such a model can be executed by the evaluation unit.

[0020] To simulate the temperature rise and / or fall in the material as realistically as possible, for example, to calculate the temperature peaks at a specific position on the wheel per wheel revolution, a more detailed thermal model of the wheel tread material is necessary, for example, for simulation using a finite element method. Calculations based on such a model can require considerable computing power and can take a long time. This typically precludes the use of such a detailed model on an evaluation unit provided directly in the vehicle.Instead, it may be provided that, based on the more detailed thermal model outside the rail vehicle, a table of temperature values ​​and / or a characteristic curve is determined, which the system then accesses; for example, a table and / or a characteristic curve may be stored on a memory unit of the system.

[0021] In this system, an average wheel temperature can be calculated using the simplified thermal model, and the locally occurring peak values ​​can be determined by looking up a table. The values ​​stored in the table were determined with greater computational effort and using more complex models. In particular, the peak values ​​determined from the table are added to the average temperature. The time-temperature curves thus obtained can be compared with material-specific curves that describe the conditions for specific changes in the metal structure.

[0022] Several conditions for the emergence of certain critical points or material changes can be checked, in particular conditions that build on one another step by step.

[0023] For example, it can first be determined whether sufficient conditions exist for the formation of austenite, such as a certain temperature increase for a certain period of time. It can also be determined whether subsequent cooling was sufficiently rapid for the formation of martensite.

[0024] In particular, the probability that martensite has formed is determined. In particular, the probability can be determined for a specific wheel, a pair of wheels, or a otherwise defined set of wheels.

[0025] For example, an error code can be generated, output and / or stored that includes a certain probability of martensite formation on a wheel.

[0026] In one embodiment of the system, the detection unit is further configured to detect a braking parameter, in particular a braking pressure of a brake cylinder and / or a braking force.

[0027] This advantageously allows for a particularly simple and direct determination of the energy that must be dissipated during braking via the contact between wheel and rail. This operating parameter is also typically particularly easily accessible via the rail vehicle's brake control system.

[0028] In a further embodiment, the operating parameter recorded for the wheel comprises a wheel speed, in particular a rotational speed of the wheel, and / or a speed of the rail vehicle.

[0029] This advantageously makes it easy to determine the kinetic energy absorbed during braking based on basic parameters of the rail vehicle's operation. Furthermore, it can be checked whether the wheel locks during braking or whether it continues to rotate. In particular, these values ​​can be easily recorded using a control device that is usually already present, which, for example, prevents the wheel from slipping during braking.

[0030] In a further development, the operating parameter recorded for the wheel comprises a time derivative of the wheel speed, in particular the rotational speed of the wheel, and / or the speed of the rail vehicle. In particular, a simple and / or multiple time derivative of the wheel speed, in particular the rotational speed of the wheel, and / or the speed of the rail vehicle, can be recorded.

[0031] This advantageously makes it particularly easy to record the dynamics of the braking event and to easily determine the energies that occur.

[0032] In one embodiment, at least one operating parameter for the wheel can be detected using an anti-skid system. For example, the detection unit is included in the anti-skid system, or the anti-skid system can be used as a detection unit.

[0033] This advantageously utilizes the capabilities of a known and possibly already existing anti-skid system, such as one integrated into a rail vehicle's brake control system, to record the operating parameter. This allows the system to be operated particularly efficiently. It can also be integrated into existing rail vehicles particularly easily, since ideally no new sensor devices need to be provided.

[0034] This means that the rail vehicle has an anti-skid system ( "wheel slide protection system", WSP), by means of which the operating parameter for the wheel is detected. Furthermore, it can be provided that at least one of several operating parameters detected for the wheel is detected by the anti-skid system.

[0035] Typically, WSP systems are already designed to record wheel speed, vehicle speed, and / or brake pressure. This makes it particularly easy to access this existing data.

[0036] According to the invention, the temperature value determined for the wheel comprises an average temperature of a wheel running surface, a temperature distribution along the wheel running surface, and a temperature at a contact surface of the wheel. In particular, it is determined whether the wheel continues to rotate during a braking event or whether it locks and slides on the rail.

[0037] This advantageously allows for direct determination of whether certain temperature-related damage is likely on the wheel. In particular, heating and / or cooling of the material can lead to phase transitions or structural changes that promote the formation of expanding damage areas, such as cracks.

[0038] In a further development, the evaluation unit is configured to determine the average temperature of the wheel's running surface using a simplified thermal model when determining the wheel temperature value and to determine temperature peaks using a lookup table. This advantageously combines an analysis method that can be executed with manageable computational effort with more complex simulation methods.

[0039] The simplified thermal model makes it possible to determine the average running surface temperature with sufficient accuracy, practically in real time, based on the recorded operating parameter. The analysis can be performed, for example, by a processing unit on the rail vehicle itself.

[0040] The determination of temperature peaks that can occur during braking is usually performed using very computationally intensive methods and therefore typically cannot be performed in real time, at least not with the usual on-board resources of a rail vehicle. Therefore, values ​​can be determined under different conditions using simulations and stored in a lookup table ( look-up table) The evaluation unit is then configured to determine and apply the value or values ​​from the lookup table that match the currently recorded operating parameters. In this case, the lookup replaces a completely new calculation and allows for sufficient accuracy of the results.

[0041] In particular, the temperature at a contact surface of the wheel with the rail can also be determined using the simplified thermal model.

[0042] In one embodiment, the control unit is configured to generate the output depending on the attainment of at least one temperature threshold. The output can also be generated depending on a temporal change in the detected operating parameter. Optionally, the control unit is further configured to determine a probability of a defect occurring, in particular a probability of martensite formation, and to generate the output depending on at least one probability threshold.

[0043] This advantageously indicates possible problems with the bike.

[0044] For example, it can be analyzed to determine the probability that certain conditions, defined based on the recorded operating parameter, can lead to certain types of damage. The output can then include information about the probability of certain problems occurring, allowing targeted countermeasures to be taken, such as specific maintenance measures.

[0045] In a further embodiment, the output includes a warning message and / or a diagnostic message and / or an error code. The control unit is optionally configured to store the output in a diagnostic memory. This allows the output to be advantageously read later, for example, by an authorized user.

[0046] The output can also be output directly. For example, a visually or acoustically perceptible signal can be generated depending on the output. For example, if the output includes a specific error code, a first signal can be output, and if the output includes another error code, a second signal can be output.

[0047] The signal can, for example, be used to issue a request to carry out a specific maintenance measure.

[0048] In the method for monitoring the condition of a wheel of a rail vehicle, at least one operating parameter for the wheel is recorded during a braking event. Based on the recorded operating parameter, a temperature value for the wheel is determined, and an output is generated and output depending on the determined temperature value.

[0049] The method is specifically designed to operate the system. It therefore offers the same advantages as the system. Fig. 1A shows an example of the system. Fig. 1B shows an embodiment of the method. Fig. 2A und 2B show schematic representations of a wheel under different braking conditions. Fig. 3 shows the temperature distribution vs. time on the wheel side at the intersection of the sample lines St and S during 5 full revolutions (assumed heat conduction: 0.5). Fig. 4 shows a cross-sectional view of a wheel and a rail. Fig. 5 shows characteristic curves concerning the formation of austenite. Fig. 6 shows characteristic curves regarding the formation of martensite.

[0050] Fig. 1A shows an embodiment of a system 100 according to the invention.

[0051] In the embodiment shown, the system 100 is integrated into a rail vehicle 10 or a subsystem of a rail vehicle 10.

[0052] The rail vehicle 10 thus has the system 100.

[0053] The system has a recording unit 20.

[0054] The detection unit 20 is part of an anti-slip device 30, which is constructed in a manner known per se in the manner of a WSP system ( wheel slide protection ) is formed.

[0055] The system 100 further comprises an evaluation unit 40.

[0056] The system 100 further comprises a control unit 50.

[0057] The detection unit 20 is configured to detect at least one operating parameter for the wheel during a braking event.

[0058] The detection unit 20 can further be configured to detect the presence of the braking event itself, for example by detecting an activity of a brake cylinder.

[0059] The evaluation unit 40 is configured to determine a temperature value for a wheel of the rail vehicle 10 based on the detected operating parameter.

[0060] The control unit 50 is configured to generate and output an output depending on the determined temperature value.

[0061] The function of system 100 can be basically described as follows: Data is acquired by the acquisition unit 20, which the evaluation unit 40 uses to monitor the temperature. In particular, a temperature or a temporal temperature development that occurs at a wheel during a braking event is determined. Based on this thermal monitoring, it is detected during ongoing operation of the rail vehicle 10 whether the conditions for a specific structural change in the wheel are present. For this purpose, known structural diagrams are used, in particular.

[0062] If it is determined that the conditions for a problematic microstructure transformation are present, a corresponding output can be generated.

[0063] The system 100 enables the following advantages: Critical wheel conditions can be detected during operation of the rail vehicle 10 and the safety of operation can be improved.

[0064] Such critical conditions may be pointed out, particularly in direct temporal connection with their occurrence and / or at a later time.

[0065] Furthermore, maintenance or repair measures may be initiated, for example to remedy damage to the wheel that occurred or is expected to occur during the braking event.

[0066] Furthermore, maintenance or preventive measures can be initiated to prevent damage before it occurs.

[0067] Furthermore, maintenance work can be carried out as needed to avoid unnecessary measures.

[0068] Fig. 1B shows an embodiment of the method which is explained below. In particular, reference is made to the method described above with reference to Fig. 1A The system is based on the exemplary embodiment explained above, which is specified in more detail in the following explanations.

[0069] In particular, a diagnostic method that can be executed by a computer device is shown.

[0070] In a step S10, at least one operating parameter for the wheel is recorded during a braking event.

[0071] In this example, a force is determined at a contact surface between the wheel and the rail.

[0072] Data about the speed of the wheel is recorded.

[0073] Furthermore, the braking force of a braking system of the rail vehicle is recorded.

[0074] In particular, the embodiment provides that a control unit of an anti-slip device (WSP) processes the detected operating parameters and data.

[0075] An energy is determined that is absorbed by the wheel via the contact surface.

[0076] The quantities that occur can include a braking force P(t) and a wheel speed V wheel (t), which each depend on the time t and are recorded in particular as a function of the time t.

[0077] In step S20, a simplified thermal model of the wheel is used. It is checked whether the wheel rotates during braking or whether it locks and slides over the rail ( wheel lock-up ) . In particular, the values ​​recorded or determined in step S10 are used in the model.

[0078] Using the simplified model, when the wheel rotates during braking, an average temperature T model (t) of the wheel tread is determined as a function of time t.

[0079] Using the simplified model, when the wheel is locked during braking, the temperature T model (t) for the contact area between the wheel tread and the rail is determined as a function of time t.

[0080] In a step S30, the temperature T model (t) determined by means of the simplified model is modified.

[0081] This involves using parameters previously determined through simulation using a FEM method. These parameters are provided, for example, by a memory unit.

[0082] A modified T modified (t) is determined as a function of time t.

[0083] In a step S40, the temperature T modified (t) thus determined is compared with a predetermined diagram which includes a characteristic curve characterising the prerequisites for austenitisation of the material of the wheel or its running surface.

[0084] An exemplary diagram 500 that can be used in step S40 is shown in Fig. 5 shown.

[0085] In particular, it is checked whether austenitization has occurred. If this is not the case, a determination is made in step S70 that there is no risk of martensite formation.

[0086] However, if it is determined in step S40 that the conditions for austenitization are met, then in a step S50 the determined

[0087] Temperature T modified (t) is compared with a given further diagram, which includes a characteristic curve that characterizes the conditions for the formation of martensite for the material of the wheel or its tread.

[0088] An exemplary diagram 600 that can be used in step S50 is shown in Fig. 6 shown.

[0089] In particular, it is checked whether the conditions for martensite formation are met, especially if the material cools sufficiently quickly. If this is not the case, it is determined again in step S70 that there is no risk of martensite formation.

[0090] However, if it is determined in step S50 that the conditions for the formation of martensite are met, such as sufficiently rapid cooling, then it is determined in step S60 that there is a risk of martensite forming.

[0091] The process then generates and displays an output. This includes, for example, an error code indicating whether or not there was a risk of martensite formation.

[0092] In a further embodiment of the method, a probability that martensite has formed is further determined in step S60. The generated output may include this probability.

[0093] Analogously, in a further embodiment of the method, a probability with which martensite has formed can be determined alternatively or additionally in step S70. The generated output can include this probability.

[0094] In particular, a threshold can be specified, and the determined value of the probability that martensite formation has occurred can be compared with the threshold. The output can then be generated based on this comparison. For example, a warning message can be generated and displayed if the threshold is exceeded.

[0095] In an anti-slip device 30, by means of which the slipping of the wheel on the rail is to be prevented, integrated sensors are provided in particular.

[0096] The detection unit 20 may comprise sensors of the type MGS3.

[0097] The values ​​and parameters recorded by the acquisition unit 20 allow the current heat on the wheel surface to be determined in real time or near real time. Even with current wheel slide protection systems (WSP, "wheel slide protection "), it cannot be avoided under all circumstances that the wheels will be overloaded, in particular due to the introduction of energy or heat during braking. However, the data recorded by the wheel slide protection system can be used to detect that sliding is occurring and / or to determine the duration of a wheel or wheelset sliding event. Using a suitable thermal model of the wheel and known material properties of the wheel, it can be determined whether and in what way transitions between different material states occur, for example between different microstructures or phases of a metal material.

[0098] Typically, larger areas of particularly hardened material are susceptible to cracks or material chipping, for example. To prevent this, a diagnostic memory can be read out at regular intervals, for example monthly or on specific occasions, such as during regular maintenance of the wheel or wheelset. Based on the data stored in the diagnostic memory, it can be determined whether the wheel should be treated using a lathe. Furthermore, based on the data stored in the diagnostic memory, it can be determined that treatment using a lathe is not necessary. Furthermore, based on the data stored in the diagnostic memory, it can be determined that a non-destructive diagnosis of the wheel or wheelset, for example using ultrasound, should be carried out in order to detect cracks and / or local changes in the hardness of the material.

[0099] Fig. 2 bis 6 show further exemplary details of the system and the method, which are explained below.

[0100] The following describes an example model that can be used to determine the formation of a potentially hardened material texture. In particular, the formation of martensite can be determined and / or the probability that martensite has formed during a braking event can be determined.

[0101] The sensors included in the detection unit measure the wheel speed, the vehicle speed and the brake pressure applied by a brake cylinder.

[0102] A simplified thermal model is accessed, which is provided, for example, by the evaluation unit.

[0103] The simplified thermal model can be provided on a plug-in card and / or a computing unit of a central control unit.

[0104] For example, the energy absorbed by the wheel is first determined, for example according to the following model, which is related to Fig. 2A und Fig. 2B as well as Fig.4 is explained: To calculate the absorbed energy for a wheelset, for example with wheels i = 1, 2, 3, 4 in the case of a wheelset with four wheels, the sliding speed is multiplied by the actual braking force at the contact between the wheel 210, 420 and the rail 440.

[0105] A contact force is determined based on the pressure of the brake cylinders.

[0106] Furthermore, the angular acceleration of the wheelset is also taken into account, where J denotes a moment of inertia of the wheels: P i = v i − v ref ⋅ F i p ci + J ⋅ v ˙ l / R 2

[0107] This refers to F i the braking force acting on a single wheel 210, 420 at the contact surface between wheel 210, 420 and rail 440. This is a direct function of the actual braking pressure p c . This function F ( p c ) can be determined using the general calculations of a braking operation, as described in UIC 544-1.

[0108] There are WSP systems that determine this force directly, recording the actual acceleration of the wheelset so that it can be used directly.

[0109] The surface temperature can then be determined, taking into account that in this case, a heat partition of approximately 50% can quickly occur, meaning that approximately 50% of the generated heat is absorbed by the wheel. This is described, for example, in PT Zwierczyk, "Thermal stress analysis of a railway wheel-rail rolling-sliding contact," Budapest 2015. Other models can assume a different partition, for example, depending on certain environmental parameters.

[0110] A simplified thermal model of the wheel 210, 420 can be determined.

[0111] In the simplified thermal model, two states are distinguished in particular: a) When the wheel 210, 420 is not rotating, i.e., when it is locked, it is assumed that the energy is absorbed via the contact point or contact area 230 between the surface of the wheel and the rail. This case is particularly Fig. 2A b) When the wheel 210, 420 rotates, it is assumed that the energy is absorbed evenly across the running surface 230 of the wheel 210, 420 at the contact points between the surface of the wheel 210, 420 and the rail 440. This case is particularly Fig. 2B shown.

[0112] In a modification of the case explained under b), it is further assumed that the heat is absorbed at a point on the contact surface between wheel 210, 420 and rail 440 and is then released again during the further rotation of the wheel 210, 420 until the point comes into contact with the rail 440 again.

[0113] Fig. 3 shows an example of a temperature profile determined using this modified model: At the temperature peaks, the observed point on the running surface of the wheel 210, 420 touches the rail 440 and absorbs heat. The contact is then broken and the point cools down again. The dashed line shows the average temperature of the wheel, and the solid line shows the temperature with additional peaks.

[0114] In Fig. 2A the model is shown for the case that the wheel rotates, while in Fig. 2B the case is shown that the wheel 210, 420 is blocked ( "lock-up" ) , wherein the wheel 210, 420 slides over the rail 440.

[0115] In a model for the Fig. 2A shown case T circle a temperature of the tread, in particular an average temperature.

[0116] In this example, the mass of the tread 220 is calculated in advance. For example, the Kalker method can be used, whereby the radius of the wheel 210 and the width of the surface 220 are determined specifically for the vehicle. Furthermore, the depth of the tread can be calculated based on simulations.

[0117] The result is something like the following: T circle . = Particio ⋅ P in − ξ circle ⋅ T circle − T 0 c ⋅ m circle T circle t = T 0 + ∑ 0 t T circle ⋅ Δ t

[0118] Furthermore, a model for the Fig. 2B In the case shown, a temperature T spot of the contact point 230. For example, the area of ​​the contact point 230 can be assumed to be approximately 1 cm 2 and 2 mm deep.

[0119] The area can be calculated specifically for the vehicle. For example, the Kalker method can be used. Furthermore, the tread depth can be calculated using simulations.

[0120] The result is something like the following: T spot . = Particio ⋅ P in − ξ spot ⋅ T spot − T 0 c ⋅ m spot T spot t = T circle + ∑ 0 t T spot . ⋅ Δ t or simplified: T spot t = T cicle + ∑ 0 t Participio ⋅ P in ⋅ Δ t c ⋅ m spot

[0121] Fig. 3 shows an example of how the temperature at a point in the running surface area of ​​the wheel 210, 420 changes during braking when the wheel 210, 420 rotates during braking. The increase in the average temperature in the running surface area is shown as the dashed line 310. Furthermore, the temperature peaks shown as the solid line 320 must be taken into account, with the peaks occurring when the point contacts the rail and absorbs energy, while the energy is subsequently released again and the temperature drops accordingly (Source: PT Zwierczyk, "Thermal stress analysis of a railway wheel-rail rolling-sliding contact", Budapest 2015).

[0122] The average temperature along the circumference of the running surface 230 changes slowly compared to the temperature peaks. The average temperature is determined using the method described above with reference to Figur 2A At least one parameter is determined in the example using a finite element method (FEM) by fitting, in particular the dashed line 310 of the Figur 3 .

[0123] The following table shows exemplary values ​​from a model used. In particular, physical constants, vehicle-specific constants, and values ​​determined by fitting during validation using an FEM method and a simulation of the temperature distribution are shown.In particular, the following are listed: the diameter of the wheel (D_wheel), the diameter of the contact area (d_spot) between wheel and rail, the thickness of the contact area in the depth of the material of the wheel (h), the area of ​​the contact area (Aspot) or the annular running surface (Aring) of the wheel, the volume of the contact area (Vspot) or the annular running surface (Vring) of the wheel, the density (ro) of the material, the mass of the contact area (mspot) or the annular running surface (mring) of the wheel, the heat transfer of the material (steel heat transfer, lam), the heat transfer of the running surface (lambda ring) or the contact area (lambda spot), the specific heat (c) of the material.

[0124] The parameters shown are also in Fig. 4 shown in an example cross-section of a wheel on a rail.

[0125] A temperature curve can now be used as a function of time, for example based on the Fig. 3 data shown.

[0126] In particular, the temperature changes during the braking event are taken into account, i.e. in particular temperature increases and temperature drops.

[0127] This checks whether a certain temperature value is reached or exceeded. When a certain temperature is reached, for example, a pearlite texture of the wheel material can be changed to an austenite structure. Such a point is, for example, in Fig. 5 marked as point "AC3", whereby diagram 500 shows exemplary characteristics of an austenitization of a steel material of the wheel.

[0128] Furthermore, it is tested whether the temperature drops so quickly after reaching the value sufficient for austenitization that martensite is formed. A corresponding characteristic curve is shown, for example, in Fig. 6 The diagram shows in particular a time-temperature conversion diagram ( continuous cooling transformation, CCT).

[0129] In the case shown, a material composition as follows is assumed: 0.33% C, 1.12% Mn, 0.30% Si, 0.027% S, 0.018% P, 0.24% Ni, 0.11% Cr, 0.04% Mo, 0.19% Cu, 0.010% Al, grain size 8-9, austenitized at 850°C (1562°F) for 1 h.

[0130] Fig. 6 shows a CCT diagram 600 for an example steel as the wheel material. This diagram relates to the texture of the material as a function of the cooling rate. LIST OF REFERENCE SYMBOLS

[0131] 10Rail vehicle 20Detection unit 30Anti-skid device; WP system 40Evaluation unit 50Control unit 100System 210Wheel 220Tread 230Contact area 310Dashed line 320Solid line 420Wheel (cross-section) 440Rail (cross-section) 500Diagram 600Diagram S10Step S20Step S30Step S40Step S50Step S60Step S70Step

Claims

1. System for monitoring the state of a wheel (210, 420) of a rail vehicle (10), comprising a recording unit (20), which is designed to record at least one operating parameter for the wheel (210, 420) during a braking event, an evaluation unit (40), which is designed to determine a temperature value for the wheel (210, 420) based on the recorded operating parameter, and a controller (50), which is designed to generate and to output an output depending on the determined temperature value, characterized in that the temperature value determined for the wheel (210, 420) comprises an average temperature of a running surface of the wheel (210, 420) and a temperature distribution along the running surface of the wheel (210, 420) and a temperature at a contact surface of the wheel (210, 420).

2. System according to claim 1, characterized in that the recording unit (20) is further designed to record a braking parameter, in particular a brake pressure of a brake cylinder and / or a braking force.

3. System according to any one of the preceding claims, characterized in that the operating parameter recorded for the wheel (210, 420) comprises a wheel speed, in particular a rotational speed of the wheel (210, 420), and / or a speed of the rail vehicle (10).

4. System according to any one of the preceding claims, characterized in that the operating parameter recorded for the wheel (210, 420) comprises a time derivative of the wheel speed, in particular of the rotational speed of the wheel (210, 420), and / or of the speed of the rail vehicle (10).

5. System according to any one of the preceding claims, characterized in that the at least one operating parameter for the wheel (210, 420) can be recorded by means of an anti-slip system (30).

6. System according to claim 1, characterized in that the evaluation unit (40) is designed to determine the average temperature of the running surface (220) of the wheel (210, 420) on the basis of a simplified thermal model when determining the temperature value for the wheel (210, 420), and to determine temperature peaks on the basis of a lookup table.

7. System according to any one of the preceding claims, characterized in that the control unit (50) is designed to generate the output depending on reaching at least one temperature threshold value, and the control unit (50) is optionally designed to determine a probability of occurrence of a damaged area, in particular a probability of the formation of martensite, and to generate the output depending on at least one probability threshold value.

8. System according to any one of the preceding claims, characterized in that the output comprises a warning message and / or a diagnostic message and / or an error code, wherein the controller (50) is optionally designed to store the output in a diagnostic memory.

9. Method for monitoring the state of a wheel (210, 420) of a rail vehicle (10), in which at least one operating parameter for the wheel (210, 420) is recorded during a braking event, a temperature value for the wheel (210, 420) is determined on the basis of the recorded operating parameter, and an output is generated and output depending on the determined temperature value, characterized in that the temperature value determined for the wheel (210, 420) comprises an average temperature of a running surface of the wheel (210, 420) and a temperature distribution along the running surface of the wheel (210, 420) and a temperature at a contact surface of the wheel (210, 420).