Diagnostic apparatus for a sand metering device for a sanding system for a rail vehicle, and method for carrying out a diagnosis for a sand metering device for a sanding system for a rail vehicle

Abstract

A diagnostic apparatus (110) for a sand metering device (SD) for a sanding system (105) for a rail vehicle (100) comprises a detection device (140) and an evaluation device (145). The detection device (140) is designed to detect at least one parameter of the sand metering device (SD) of the sanding system (105) and to provide a detection signal (150) representing the parameter. The evaluation device (145) is designed to output a metering error signal (155) using the detection signal (150), which metering error signal indicates a malfunction of the sand metering device (SD) if the parameter deviates from a target parameter.

Description

[0001] The present approach relates to a diagnostic device for a sand dispenser for a sanding system for a rail vehicle and a method for performing a diagnosis for a sand dispenser for a sanding system for a rail vehicle.

[0002] Sanding systems on rail vehicles are used to apply sand or other bulk material to the rail in front of the wheel rolling over the sand, or directly into the wheel gap, in order to increase the coefficient of friction between the wheel and the rail or to restore it to its original value. This measure can improve traction and braking of a rail vehicle. Sanding systems are often considered systems that contribute significantly to the risk reduction of accidents involving significant property damage, personal injury, or fatalities, as braking distances can be shortened when braking with the sand application activated. The sand dosing unit, which comprises a sand dosing device and a sand conveying device, is an essential component of the sanding system.

[0003] The document DE 10 2011 113 085 A1 shows a particle scattering system for a rail vehicle.

[0004] The document DE 10 2013 016 881 A1 shows a dispensing device for friction coefficient modifiers for a rail vehicle.

[0005] The document DE 102011112969 A1 shows a particle scattering system for a rail vehicle.

[0006] The document DE 20 2014104156 U1 shows a device for monitoring the flow of liquid or solid media transported by compressed air, in particular sand, a sand spreading device for vehicles and a vehicle with such a sand spreading device.

[0007] Against this background, the object of the present approach is to provide an improved diagnostic device for a sand dosing device for a sanding system for a rail vehicle and an improved method for performing a diagnosis for a sand dosing device for a sanding system for a rail vehicle.

[0008] This object is achieved by a diagnostic device having the features of device claim 1, by a method according to claim 10 and by a computer program according to claim 11.

[0009] The advantages achieved with the presented approach are the creation of a diagnostic device that quickly and easily detects a malfunction of a sand dispenser in a sanding system. This allows a rail vehicle's sanding process to be monitored and a defect corrected if necessary. This creates the opportunity to significantly increase safety during a rail vehicle braking process.

[0010] A diagnostic device for a sand dispenser for a sanding system for a rail vehicle comprises a detection device and an evaluation device. The detection device is designed to detect at least one parameter of the sand dispenser of the sanding system and to provide a detection signal representing the parameter. The evaluation device is designed to use the detection signal to output a dosing error signal that indicates a malfunction of the sand dispenser if the parameter deviates from a target parameter.

[0011] The sand dosing device is to be understood as a unit comprising at least one sand dosing device and, additionally or alternatively, a sand conveying device. The sand dosing device is designed to dose a quantity of sand or any other bulk material to be applied during sanding. The sand conveying device is designed to convey the sand or bulk material onto the rail or into the wheel rail gap, for example using compressed air. The parameter can be any operating parameter during operation of the sand dosing device, for example a sensor value of the sand dosing device sensed during operation of the sand dosing device or a sensor value of the sand conveying device sensed during operation of the sand conveying device.The target parameter can be a comparison value stored or read by the diagnostic device, which can be compared with the parameter in the evaluation device. The detection device can have at least one sensor for sensing the parameter and, additionally or alternatively, a provision device for providing the detection signal. The detection device can, for example, be arranged in or on the sand dispenser, and the evaluation device can be arranged or implemented in a sanding control system of the sand dispenser. Such a diagnostic device advantageously makes it possible to monitor the operation of the sand dispenser and to detect a malfunction.

[0012] The detection device is configured to detect a position of a reciprocating piston of the sand dosing device of the sanding system as the parameter and to provide a position signal representing the position as the detection signal. The evaluation device is configured to use the position signal as the dosing device error signal to output a sand dosing error signal, which indicates a malfunction of the sand dosing device if the position deviates from a target position. The target position can represent a target position of the reciprocating piston required depending on a requested sanding process. Thus, based on the actual position of the reciprocating piston, it can be determined whether the sanding process is being carried out correctly.

[0013] It is further advantageous if the diagnostic device has an activation device configured to output an activation signal designed to cause the piston to move to the desired position. This allows for active verification of a correct sanding process.

[0014] The activation device can, for example, be configured to output the activation signal designed to cause the piston movement of the reciprocating piston to the desired position, which represents an open position of the reciprocating piston. The open position is understood to be an open state of the reciprocating piston in which sand dispensing is possible. This allows verification of whether a requested sand dispensing can actually occur.

[0015] According to one embodiment, the activation device can be configured to automatically output the activation signal in response to a manually initiated, read-in actuation and, additionally or alternatively, at a defined time interval, in particular at a pulse-width modulation interval. For example, a rail vehicle driver can check at any time, for example by pressing a corresponding button, whether the reciprocating piston can be properly moved into the open position. Automatic checking at a defined time interval enables a regular and thus particularly reliable checking method.

[0016] The detection device can, for example, be configured to detect an open position of the reciprocating piston as the position and to provide an open signal representing the open position, and additionally or alternatively to detect a closed position of the reciprocating piston and to provide a closed signal representing the closed position, and additionally or alternatively to detect at least one intermediate position of the reciprocating piston between the open position and the closed position and to provide a intermediate signal representing the intermediate position. Thus, the dosing error signal can be output, for example, if, in response to the output of the activation signal, the closed signal and additionally or alternatively the intermediate signal are read within a defined period of time, and additionally or alternatively no open signal is read.However, if the open signal is read in response to the activation signal, no dosing error signal can be output because in such a case the reciprocating piston performs the correct requested movement.

[0017] It is further advantageous if, according to one embodiment, the detection device is designed to detect a delivery pressure of a sand delivery device of the sanding system as the parameter and to provide a delivery pressure signal representing the delivery pressure as the detection signal. The evaluation device is designed to use the delivery pressure signal as the dosing device error signal to output a pressure error signal that indicates a malfunction of the sand delivery device if the delivery pressure deviates from a target delivery pressure. A correct delivery pressure is also essential for carrying out a sanding process. In such an embodiment, a current delivery pressure can be used to check the sand delivery device. The target delivery pressure can be a stored value.

[0018] The detection device can comprise at least one reed sensor, proximity sensor, microswitch, triangulation rangefinder, permanent magnet, and additionally or alternatively at least one discharge pressure sensor. Such sensors are suitable for detecting one of the parameters described above, for example, for detecting the position of the reciprocating piston and additionally or alternatively for detecting the discharge pressure of the sand conveying device.

[0019] The evaluation device can further be configured to output a dosing function signal using the detection signal, indicating correct function of the sand dosing device when the parameter matches the target parameter. Thus, the evaluation device can be configured to output a sand dosing function signal using the position signal, indicating correct function of the sand dosing device when the position matches the target position, and additionally or alternatively, to output a pressure function signal using the delivery pressure signal, indicating correct function of the sand delivery device when the delivery pressure matches the stored target delivery pressure. This provides a way to also identify a positive test result.

[0020] According to an advantageous embodiment, the evaluation device can be configured to output the dosing device error signal, which is configured to indicate the malfunction of the sand dosing device to a driver of the rail vehicle visually, haptically, and additionally or alternatively acoustically. The malfunction can be indicated to the driver, for example, visually, haptically, and additionally or alternatively acoustically. This allows the driver to detect the malfunction and initiate repair of the affected device as quickly as possible.

[0021] A method for performing a diagnosis for a sand dispenser for a sanding system for a rail vehicle comprises a detection step and an output step. In the detection step, a parameter of the sand dispenser is detected and a detection signal representing the parameter is provided. In the output step, a dosing device error signal is output using the detection signal if the parameter deviates from a target parameter, wherein the dosing device error signal indicates a malfunction of the sand dispenser.

[0022] This method can be implemented, for example, in software or hardware or in a mixed form of software and hardware, for example in a control unit.

[0023] Also advantageous is a computer program product or computer program with program code that can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and is used to carry out, implement and / or control the steps of the method according to one of the embodiments described above, in particular when the program product or program is executed on a computer or a device.

[0024] Examples of the approach presented here are explained in more detail in the following description with reference to the figures. They show: Fig. 1 a schematic representation of a rail vehicle with a sanding system with a sand dispenser and a diagnostic device according to an embodiment; Fig. 2 a schematic representation of a diagnostic device according to an embodiment; and Fig. 3 a flowchart of a method for performing a diagnosis for a sand dispenser for a sanding system for a rail vehicle according to an embodiment.

[0025] In the following description of advantageous embodiments of the present approach, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, whereby a repeated description of these elements is omitted.

[0026] Fig. 1 shows a schematic representation of a rail vehicle 100 with a sanding system 105 with a sand dispenser SD and a diagnostic device 110 according to an embodiment.

[0027] The sanding system 105 is configured to perform a sanding process of the rail vehicle 100. During the sanding process, sand or another bulk material is placed on a rail 120 in front of the wheel RD rolling over the sand, or directly into a wheel rail gap 130, in order to increase the coefficient of friction between the wheel RD and the rail 120 or to bring it to an originally higher value, thereby braking the rail vehicle 100. According to this exemplary embodiment, the wheel RD is one of four wheels RD connected to the vehicle 100 by means of a bogie DG. An arrow indicates a direction of travel 135 of the rail vehicle 100.

[0028] According to this exemplary embodiment, the sanding system 105 comprises a sandbox SK for storing sand, the sand dosing device SD, and / or a sand pipe SR for directing the sand in front of the wheel RD or into the wheel rail gap 130. According to this exemplary embodiment, the sand dosing device SD is arranged between the sandbox SK and the sand pipe SR and comprises at least one sand dosing device and / or a sand conveying device. The sand dosing device is designed to dose a quantity of sand or any other bulk material to be applied during the sanding process. The sand conveying device is designed to convey the sand or the bulk material onto the rail 120 or into the wheel rail gap 130.

[0029] The diagnostic device 110 has a detection device 140 and an evaluation device 145. The detection device 140 is designed to detect at least one parameter of the sand dosing device SD of the sanding system 105 and to provide a detection signal 150 representing the parameter. The evaluation device 145 is designed to output a dosing device error signal 155 using the detection signal 150, which indicates a malfunction of the sand dosing device SD if the parameter deviates from a target parameter.

[0030] For example only, the detection device 140 according to this exemplary embodiment is implemented on or in the sand dispenser SD and / or the evaluation device 145 is implemented in a sanding control 160 of the sanding system 105. According to this exemplary embodiment, the sanding control 160 is signal-connected to a vehicle control 165 of the rail vehicle 100. According to this exemplary embodiment, the vehicle control 165, in turn, has a communication interface to a vehicle driver 170 of the rail vehicle 100.

[0031] According to this exemplary embodiment, the parameter of the sand dosing device SD is any operating parameter during operation of the sand dosing device SD, for example, a sensor value of the sand dosing device sensed during operation of the sand dosing device and / or a sensor value of the sand conveying device sensed during operation of the sand conveying device. According to one exemplary embodiment, the target parameter is a comparison value stored internally in the sanding control 160 and readable in the form of a target parameter signal 175, or a comparison value readable externally by the diagnostic device 110 in the form of the target parameter signal 175 from the sanding control 160. According to one exemplary embodiment, the evaluation device 145 is designed to compare the parameter with the target parameter. According to one exemplary embodiment, the detection device 140 has at least one sensor for detecting the parameter.According to this embodiment, the evaluation device 145 is further configured to output an activation signal 180 to cause a function of the sand dosing device SD to obtain the parameter.

[0032] Thanks to the diagnostic device 110 presented here, it is possible to detect a failure of the sand dosing device and / or sand conveying device during ongoing driving operation and / or to check the function of the sand dosing and sand conveying device at regular intervals without interrupting the paint operation.

[0033] It is therefore advantageous to include the sanding system 105 in risk-reducing measures - specifically in braking distance-reducing measures.

[0034] The approach presented here relates to a diagnostic device 110 for a mechanical sand dosing device and a pneumatic sand conveying device of the sanding system 105 of the rail vehicle 100, wherein the sand dosing device is realized according to one embodiment by at least one electrically or pneumatically operated dosing piston, which is opened and closed in periodic patterns during dosing.

[0035] Fig. 2 shows a schematic representation of a diagnostic device 110 according to an embodiment. This may be an embodiment of the device described with reference to Fig. 1 described diagnostic device 110.

[0036] According to this exemplary embodiment, the detection device 145 is designed to detect a position of the metering piston, also referred to below as the "stroke piston" HK, of the sand metering device SDE of the sanding system 105 as the parameter and to provide a position signal 200 representing the position as the detection signal. The evaluation device 145 is designed to output a sand metering error signal using the position signal 200 as the metering device error signal 155, which indicates a malfunction of the sand metering device SDE if the position deviates from a target position. According to one exemplary embodiment, the target position represents a target position of the stroke piston HK required depending on a requested sanding process.

[0037] According to this exemplary embodiment, the diagnostic device 110 has an activation device 205 which is designed to output the activation signal 180, which is designed to cause a piston movement of the reciprocating piston HK to the target position. According to this exemplary embodiment, the activation device 205 is designed to output the activation signal 180, which is designed to cause the piston movement of the reciprocating piston HK to the target position, which represents an open position of the reciprocating piston HK. The open position is to be understood as an open state of the reciprocating piston HK, in which a dispensing of sand is only possible. According to one exemplary embodiment, the activation signal 180 causes an activation of a lifting magnet HM of the sand dosing device SDE such that the reciprocating piston HK is opened and closed in periodic patterns.According to this exemplary embodiment, the activation device 205 is configured to automatically output the activation signal 180 in response to a manually initiated, read-in actuation and / or at a defined time interval, in particular at a pulse-width modulation interval. According to one exemplary embodiment, the activation signal 180 is output during a sanding process as a pulse-width modulation signal, or "PWM signal" for short, with a frequency of 3.3 Hz and / or a duty cycle between 30 percent and 60 percent.

[0038] According to this exemplary embodiment, the detection device 140 is designed to detect the open position of the reciprocating piston HK as the position and to provide an open signal 230 representing the open position and / or to detect a closed position of the reciprocating piston HK and to provide a closed signal 215 representing the closed position and / or to detect at least one middle position of the reciprocating piston HK between the open position and the closed position and to provide a middle signal representing the middle position. According to one exemplary embodiment, the evaluation device 145 is designed to output the dosing device error signal if, in response to an output of the activation signal 180, the closed signal and / or the middle signal are read in within a defined period of time and / or no open signal 230 is read in.

[0039] To detect the position, the detection device 140 according to this exemplary embodiment has at least one reed sensor 220, proximity sensor, microswitch, triangulation distance meter, and / or permanent magnet. According to this exemplary embodiment, the reed sensor 220 has a reed contact pair, which according to this exemplary embodiment is arranged in a closed position RS-G in the closed position of the reciprocating piston HK, in which the reed sensor 220 according to this exemplary embodiment provides the closed signal 215. According to one exemplary embodiment, the reed contact pair is arranged in a closed position in the closed position of the reciprocating piston HK, in which the reed sensor 220 provides the closed signal, and / or in the center position of the reciprocating piston HK, in which the reed sensor 220 also provides the open signal.

[0040] According to this exemplary embodiment, the detection device 140 has at least one further reed sensor 225, which has a further reed contact pair, which, according to this exemplary embodiment, is arranged in an open position RS-O in the open position of the reciprocating piston. The further reed sensor 225 is designed to provide, as a further position signal 200, a first feedback signal 230 to the evaluation device 145, representing an open position RS-O of the further reed contact pair, and / or to provide a second feedback signal to the evaluation device 145, representing a closed position of the further reed contact pair.

[0041] According to this exemplary embodiment, the detection device 140 is configured to detect a delivery pressure of the sand conveying device SFE of a sand conveyor SF of the sand dosing device SD of the sanding system as the parameter and to provide a delivery pressure signal 233 representing the delivery pressure as the detection signal. The evaluation device 145 is configured to use the delivery pressure signal 233 as the dosing device error signal 155 to output a pressure error signal indicating a malfunction of the sand conveying device SFE if the delivery pressure deviates from a target delivery pressure. According to this exemplary embodiment, the target delivery pressure is a stored value.

[0042] To detect the conveying pressure, the detection device 140 according to this exemplary embodiment has at least one conveying pressure sensor FDS. In response to a further activation signal 235 output by the sanding control 160 or the evaluation device 145, a solenoid valve MV is opened according to this exemplary embodiment. This solenoid valve is connected via a shut-off valve AH to a compressed air tank of a main air tank line HBL of the rail vehicle. The conveying pressure sensor FDS is arranged and designed to sense the conveying pressure of a conveying air 240, which is fed into the sand conveyor SF during the sanding process in order to effect a sand flow 245 of the metered sand through the sand pipe SR.

[0043] According to this exemplary embodiment, the evaluation device 145 is further configured to output a dosing function signal 250 using the detection signal, which indicates correct function of the sand dosing device SD when the parameter matches the target parameter. Thus, according to this exemplary embodiment, the evaluation device 145 is configured to output a sand dosing function signal using the position signal 200, which indicates correct function of the sand dosing device SDE when the position matches the target position, and / or to output a pressure function signal using the delivery pressure signal 233, which indicates correct function of the sand delivery device SFE when the delivery pressure matches the stored target delivery pressure.

[0044] According to this exemplary embodiment, the evaluation device 145 is designed to output the dosing device error signal 155, which is designed to indicate the malfunction of the sand dosing device SD to the driver of the rail vehicle in a visually, haptically and / or acoustically perceptible manner and / or to indicate the dosing device function signal 250 to the driver in a visually, haptically and / or acoustically perceptible manner.

[0045] A fundamental concept of the invention is to detect the position of the reciprocating piston HK using sensors 220, 225. The position of the reciprocating piston HK to be detected is at least the open position. According to one exemplary embodiment, further advantageously detected positions are, in order, the closed position, the center position, and / or a continuously detected position of the reciprocating piston HK. Suitable sensors 220, 225 for position detection include, among others, reed contacts, inductive proximity sensors, microswitches, and triangulation distance meters, according to one exemplary embodiment. From a temporal position detection, the evaluation device 145 can infer a function or failure of the reciprocating piston HK. Furthermore, the evaluation device 145 can infer the amount of sand applied.According to one embodiment, the evaluation device 145 is designed to detect an incorrect activation of the sanding process if it is recognized that the reciprocating piston HK executes a movement despite the missing activation signal 180.

[0046] According to one embodiment, a regular check of the function of the dosing device SDE is realized by very briefly activating the reciprocating piston HK, thus with or without significant sand discharge, and the corresponding check of the reciprocating piston movement by the activation signal 180. Additionally or alternatively, according to one embodiment, a regular check of the function of the sand conveying device SFE is realized by briefly activating the delivery pressure by the further activation signal 235, thus with or without significant air loss, and the corresponding check of the built-up delivery pressure. An excessively high delivery pressure indicates a blockage in the system, and an excessively low delivery pressure indicates a leak in the system.This results in the advantage that the sand dosing device SDE and / or sand conveying device SFE can be tested at any time and as often as required without a significant amount of sand or air escaping and without restricting driving operations.

[0047] The following is a description of two application examples of the diagnostic device 110 presented here in connection with an electric reciprocating piston HK with at least two reed contacts as position sensors of the reciprocating piston HK.

[0048] The first application example describes a sanding request with diagnosis using the diagnostic device 110 presented here: The vehicle driver or, for example, the wheel slide protection system requests sanding from the sanding control unit 160 via the vehicle control system while driving. The sanding control unit 160 activates the sand dosing device SDE and the sand conveying device SFE of the sand doser SD. The lifting magnet HM of the sand dosing device SDE is periodically activated via a PWM signal, and the lifting piston HK is moved accordingly. A permanent magnet is mounted on the lifting piston HK. The reed contacts 220, 225, which are mounted in a suitable position near the permanent magnet of the lifting piston HK, detect these periodic position changes of the lifting piston HK. These position signals 200 are received and evaluated by the sanding control unit 160, here the evaluation unit 145. The activation signals 180 are compared with the position signals 200.Any deviation between the signals is detected as an error. The correct or incorrect execution of the sanding request is reported to the vehicle control system, which forwards this to the vehicle driver. At the same time, the sand conveyor SF is supplied with conveying air 240, which is activated by the solenoid valve MV controlled by the sanding control system 160. The conveying pressure sensor FDS reports the applied pressure and thus the correct or incorrect function back to the sanding control system 160, in this case the evaluation device 145. The applied conveying pressure (feedback signal) is compared with the stored target pressure. Any deviation between the signals is detected as an error. The correct or incorrect execution of the sanding request is also reported here to the vehicle control system, which forwards this to the vehicle driver.

[0049] The second application example describes an automatic diagnostic request using the diagnostic device 110 presented here: The diagnostic request is automatically triggered at regular intervals by the sanding control 160, in this case the evaluation device 145. The process corresponds to that of the sanding request, except that the request triggered by the activation signal 180 is selected to be so short that the lifting piston HK can only complete one complete stroke from the closed position to the open position and back, and the delivery pressure triggered by the further activation signal 235, assuming correct function, has the opportunity to build up to the target pressure. Here too, the correct or incorrect execution of the diagnostic request is reported to the vehicle control system, which reports this to the vehicle driver in the event of a negative result, i.e. failure of the sand dosing device SDE.

[0050] Fig. 3 shows a flowchart of a method 300 for performing a diagnosis for a sand dispenser for a sanding system for a rail vehicle according to an embodiment. This method 300 is different from the method shown in Fig. 1 or 2 described diagnostic device can be controlled and / or carried out.

[0051] The method 300 comprises a detection step 305 and an output step 310. In detection step 305, a parameter of the sand dosing device is detected and a detection signal representing the parameter is provided. In output step 310, a dosing device error signal is output using the detection signal if the parameter deviates from a target parameter, wherein the dosing device error signal indicates a malfunction of the sand dosing device.

[0052] If an embodiment includes an "and / or" link between a first feature and a second feature, this should be read as meaning that the embodiment according to one embodiment has both the first feature and the second feature and according to another embodiment has either only the first feature or only the second feature. LIST OF REFERENCE SYMBOLS

[0053] AHShut-off valve DGBogie FDSDelivery pressure sensor HBLMain air reservoir line HKReciprocating piston HMLifting magnet MVSolenoid valve RDWheel RS-OSensor detecting open HK position RS-GSensor detecting closed HK position SDSand dosing device SDESand dosing device SFSand conveyor SFESand conveyor device SKSand box SRSand pipe 100Rail vehicle 105Sanding system 110Diagnostic device 120Rail 130Wheel rail gap 135Direction of travel 140Detection device 145Evaluation device 150Detection signal 155Dosing error signal 160Sanding control 165Vehicle control 170Vehicle driver 175Setpoint parameter signal 180Activation signal 200 Position signal 205 Activation device 215 Open signal 220 Reed sensor 225 Additional reed sensor 230 Closed signal 233 Conveying pressure signal 235 Additional activation signal 240 Conveying air 245 Sand flow 250 Dosing function signal 300Method for performing a diagnosis for a sand dispenser for a sanding system for a rail vehicle 305Step of detection 310Step of output

Claims

1. Diagnostic apparatus (110) for a sand metering device (SD) for a sanding system (105) for a rail vehicle (100), wherein the diagnostic apparatus (110) comprises the following features: a detection device (140), which is configured to detect at least one parameter of the sand metering device (SD) of the sanding system (105) and to provide a detection signal (150) representing the parameter, and an evaluation device (145), which is configured to output a metering error signal (155) using the detection signal (150), which metering error signal indicates a malfunction of the sand metering device (SD) when the parameter differs from a target parameter, characterized in that the detection device (140) is configured to identify as the parameter a position of a reciprocating piston (HK) of a sand metering device (SDE) of the sanding system (105) and to provide as the detection signal (150) a position signal (200) representing the position, wherein the evaluation device (145) is configured to output a sand metering error signal using the position signal (200) as the metering error signal (155), which sand metering error signal indicates a malfunction of the sand metering device (SDE) if the position deviates from a target position.

2. Diagnostic apparatus (110) according to claim 1, comprising an activation device (205), which is configured to output an activation signal (180) which is configured to cause a piston movement of the reciprocating piston (HK) to the target position.

3. Diagnostic apparatus (110) according to claim 2, wherein the activation device (205) is configured to output the activation signal (180) which is configured to cause the piston movement of the reciprocating piston (HK) to the target position, which target position represents an opened open position of the reciprocating piston (HK).

4. Diagnostic apparatus (110) according to claim 2 or 3, wherein the activation device (205) is configured to automatically output the activation signal (180) in response to a manually read-in actuation and / or at a defined time interval, in particular at a pulse width modulation interval.

5. Diagnostic apparatus (110) according to any one of the preceding claims, wherein the detection device (140) is configured to detect an open position of the reciprocating piston (HK) as the position, and to provide an open signal (215) representing the open position, and / or to detect a closed position of the reciprocating piston (HK), and to provide a closed signal representing the closed position, and / or to detect at least one central position of the reciprocating piston (HK) between the open position and the closed position, and to provide a central signal representing the central position.

6. Diagnostic apparatus (110) according to any one of the preceding claims, wherein the detection device (140) is configured to detect, as the parameter, a conveying pressure of a sand conveying device (SFE) of the sanding system (105), and to provide, as the detection signal (150), a conveying pressure signal (233) representing the conveying pressure, wherein the evaluation device (145) is configured to output a pressure error signal using the conveying pressure signal (233) as the metering error signal (155), which pressure error signal indicates a malfunction of the sand conveying device (SFE) if the conveying pressure deviates from a target conveying pressure.

7. Diagnostic apparatus (110) according to any one of the preceding claims, wherein the detection device (140) comprises at least one reed sensor (220, 225), proximity sensor, microswitch, triangulation range finder, permanent magnet and / or at least one conveying pressure sensor (FDS).

8. Diagnostic apparatus (110) according to any one of the preceding claims, wherein the evaluation device (145) is configured to output a metering function signal (250) using the detection signal (150), which metering function signal indicates a correct function of the sand metering device (SD) if the parameter corresponds to the target parameter.

9. Diagnostic apparatus (110) according to any one of the preceding claims, wherein the evaluation device (145) is configured to output the metering error signal (155) which is configured to indicate perceptibly the malfunction of the sand metering device (SD) to a driver (170) of the rail vehicle (100).

10. Method (300) for performing a diagnosis for a sand metering device (SD) for a sanding system (105) for a rail vehicle (100), wherein the method (300) comprises the following steps: detecting (305) a parameter of the sand metering device (SD) and providing a detection signal (150) representing the parameter, and outputting (310) a metering error signal (155) using the detection signal (150), if the parameter deviates from a target parameter, wherein the metering error signal (155) indicates a malfunction of the sand metering device (SD), characterized in that in the detection step (305), a position of a reciprocating piston (HK) of a sand metering device (SDE) of the sanding system (105) is detected as the parameter, and a position signal (200) representing the position is provided as the detection signal (150), wherein in output step (310), using the position signal (200) as the metering error signal (155), a sand metering error signal is output, which indicates a malfunction of the sand metering device (SDE) if the position differs from a target position.

11. Computer program which is configured to execute and / or control the method (300) according to claim 10.

12. Machine-readable storage medium, on which the computer program according to claim 11 is stored.

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