Method and device for determining the air consumption of an air spring

Abstract

The invention relates to a method for determining the air consumption (L) of an air spring (2) during operation, wherein the air spring (2) is connected to a compressed air supply (4) via a pipe (3) and the compressed air supply (4) to the air spring (2) is provided by means of switching elements (5), the method comprising the steps: - Determining or specifying a flow resistance (S) of the pipe (3) as a function of the pressure difference, - Measuring a spring air pressure (F) in the air spring (2) during operation, - Measuring a supply air pressure (V) of the compressed air supply (4) during operation, - Determining actuation times (A) of the switching elements (5) during operation, - Determining the air consumption (L) of the air spring (2) based on the determined flow resistance (S), the spring air pressure (F), the supply air pressure (V) and the actuation times (A) of the switching elements (5), - Outputting information about the air consumption (L).Furthermore, the invention comprises a device and a vehicle.

Description

[0001] The invention relates to a method and a device for determining the air consumption of an air spring during operation and to a vehicle.

[0002] The air consumption of an air suspension system in multiple units is unknown during operation due to the pneumatic control system. Therefore, estimating consumption for future projects to determine the required compressors is unreliable, as there is little field data available, and that data is derived from specialized and complex test runs. Furthermore, incipient damage to the air spring bellows, which would be indicated by increased air consumption, cannot be detected.

[0003] Previously, air consumption was determined based on simulations and a few specialized and complex field tests. Air spring monitoring is based on air spring pressure and only activates when significant damage (e.g., a burst) occurs. Pre-existing damage is not detected. A train with a burst air spring experiences significant operational limitations.

[0004] It is an object of the present invention to provide a method and a device for determining the air consumption of an air spring and a vehicle with which the disadvantages described above are avoided.

[0005] This problem is solved by a method according to claim 1, a device according to claim 10 and a vehicle according to claim 11.

[0006] A method according to the invention serves to determine the air consumption of an air spring during operation, wherein the air spring is connected to a compressed air supply via piping and the compressed air supply to the air spring is controlled by switching elements (e.g., solenoid valves). The method comprises the following steps: - Determining or specifying a flow resistance of the piping depending on the pressure difference, - Measuring the spring air pressure in the air spring during operation, - Measuring the supply air pressure of the compressed air supply during operation, - Determining the actuation times of the switching elements during operation, - Determining the air consumption of the air spring based on the determined

[0007] Flow resistance, spring air pressure, supply air pressure and control times of the switching elements (e.g. by means of physical pressure equations), - output of information about air consumption.

[0008] The present method serves to precisely determine the air consumption of an air spring during operation, e.g., in a rail vehicle. The core of the process comprises five steps.

[0009] First, the flow resistance of the piping is determined or specified. This is necessary to know how much of the compressed air supply pressure actually reaches the air spring. Flow resistance describes the resistance that air encounters as it flows through the piping from the compressed air supply to the air spring. This value can be determined experimentally, for example, by measuring the pressure supplied by the compressed air system and the pressure reaching the spring at different supply pressures. However, flow resistance can also be calculated using formulas known in the art if the dimensions of the piping are known, in particular pipe lengths, pipe diameters, and the number and bend radii of any curves. The surface roughness of the inner surfaces of the piping can also be taken into account.

[0010] For this process, the flow resistance can be defined as a function of the compressed air supply pressure or as a list for various compressed air supply pressures. The specified value can then be retrieved by selecting the values ​​from the function or the list.

[0011] In this method, the air pressure within the air spring is measured during operation. This can be done using pressure sensors, e.g., a piezoelectric pressure sensor, placed inside or (directly) in front of the air spring. The precise method for performing the pressure measurement is known in the prior art.

[0012] Furthermore, the supply air pressure of the compressed air system is measured during operation. This can be done, for example, (directly) at the outlet of the compressed air supply using a pressure sensor.

[0013] These two values ​​can be used, for example, to determine the flow resistance of the piping and, by comparing it with the specified flow resistance, to deduce damage to the piping or the air spring.

[0014] The actuation times of the switching elements (e.g., solenoid valves) are also determined during operation. Typically, there is one switching element that controls the flow of air from the compressed air supply to the air spring ("supply valve") and one that controls the flow from the air spring to the environment ("vent valve"). If pressure is to be built up in the air spring, the vent valve is closed and the supply valve is open; if pressure is to be reduced, the supply valve is closed and the vent valve is open. All switching elements can also be closed to maintain pressure in the air spring.

[0015] When measuring actuation times, the periods during which the switching elements (e.g., valves) are open or closed are recorded to control the air supply to the air spring. This information can usually be retrieved directly from the control electronics, or the switching elements can be monitored.

[0016] This allows a decision to be made as to when exactly the supply air pressure of the compressed air supply should correlate with the spring air pressure in the air spring, namely when the vent valve is closed and the supply valve is open, or when the pressure of the air spring should decrease according to a determined venting flow resistance, namely when the supply valve is closed and the vent valve is open.

[0017] Using the data collected in the previous steps (flow resistance, spring air pressure, supply air pressure, and actuation times), the actual air consumption of the air spring can now be calculated. The resulting air consumption information can then be displayed in a report, on a dashboard, or directly to the operating personnel. The data can also be used to identify faults in the air spring or the piping.

[0018] Regarding air consumption, whenever the air spring is vented, for example, when the vent valve is opened, air is "consumed," meaning it is released from the system. This air must be replenished by the compressed air supply when the air spring is to be extended again. The measured pressures at the different actuation states of the switching elements (known from the actuation times) allow the air consumption to be determined using physical pressure equations.

[0019] A device according to the invention serves to determine the air consumption of an air spring during operation, wherein the air spring is connected to a compressed air supply via piping and the compressed air supply to the air spring is controlled by switching elements. The device comprises the following components: - an air spring measuring unit, designed to measure the spring air pressure in the air spring during operation, - a supply measuring unit, designed to measure the supply air pressure of the compressed air supply during operation, - a switching measuring unit designed to determine the actuation times of the switching elements during operation, - a determination unit designed to determine the air consumption of the air spring based on the determined flow resistance, the spring air pressure, the supply air pressure and the actuation times of the switching elements, - a data interface designed to output information about air consumption.

[0020] The function of the device's components has already been described. The device is preferably designed for carrying out a method according to the invention.

[0021] The air spring measuring unit is designed to measure the pressure inside the air spring during operation. Pressure sensors are typically used for this purpose. The measured data is transmitted to the control unit to calculate air consumption. For example, the air spring measuring unit can use a piezoresistive pressure sensor to measure spring air pressures.

[0022] The supply measuring unit measures the pressure supplied by the compressed air system while the air spring is in operation. Pressure sensors are often used here as well. The measured supply air pressures are also factored into the calculation of air consumption by the determining unit. For example, the supply measuring unit can use a capacitive pressure sensor to measure supply air pressures.

[0023] The switching and measuring unit is responsible for determining the actuation times of the switching elements (such as valves) that control the air supply and / or venting to the air spring. Signals are often taken directly from the control electronics for this purpose. The recorded actuation times are crucial for the calculation of the exact air consumption by the measuring unit.

[0024] The determining unit is preferably a processing unit. It processes the data supplied by the other components (flow resistance, spring air pressure, supply air pressure, and actuation times) and calculates the air consumption of the air spring based on this data. It preferably uses all collected information to provide a precise picture of the air consumption.

[0025] The data interface enables the output of information calculated from air consumption to various recipients or systems, such as operators, monitoring devices, or databases. It ensures that the results of the determining unit are communicated effectively and efficiently.

[0026] The measured air consumption can be directly compared during operation to identify faulty air springs exhibiting high consumption. It can also be transmitted to a central control unit (e.g., a headquarters) to determine statistical parameters for designing compressed air supply systems in new rail vehicles.

[0027] A vehicle according to the invention is in particular a rail vehicle and comprises an air spring system and a device according to the invention, which is designed to determine the air consumption of the air spring system.

[0028] Further, particularly advantageous embodiments and developments of the invention result from the dependent claims and the following description, wherein the claims of one claim category may also be further developed analogously to the claims and description parts of another claim category and, in particular, individual features of different embodiments or variants may be combined to form new embodiments or variants.

[0029] According to a preferred embodiment of the method, the switching elements are controlled valves, preferably solenoid valves. These are well known and proven in the prior art.

[0030] Basically, any sensor capable of measuring air pressure and outputting the measured values ​​as electrical signals is suitable as a pressure sensor. Piezoelectric, capacitive, or resistive pressure sensors are preferred.

[0031] Preferably, geometric data relating to the diameter and structure of the piping are provided to determine the flow resistance. This geometric data includes, for example, the diameter and length of pipes, the number and radii of bends, and, if applicable, the roughness of the inner surfaces. Using this geometric data, the flow resistance can be determined according to known formulas.

[0032] Preferably, pressure differential measurements are taken during operation at different pressure conditions to determine the flow resistance. These measurements are preferably stored and can be stored, for example, in a list assigned to their respective pressures. In this way, a flow resistance can be determined quite accurately for different pressures. A mathematical function of flow resistance versus pressure can also be derived from the measurements.

[0033] As long as the piping remains unchanged, the known values ​​can be used to determine air consumption. If the piping changes, new values ​​should be taken or calculated.

[0034] It is preferred that in one embodiment of the method, damage to the air spring is detected from the air consumption of the air spring, in particular from a change in air consumption over time.

[0035] For example, with the switching elements closed, it can be checked whether the pressure in the air spring decreases over time. Similarly, with the vent valve closed and the supply valve open, it can be determined whether the air spring pressure rises within a predefined range (dependent on flow resistance). It should be noted, however, that all of this is done during operation. For example, normal driving may occur, during which vibrations lead to pressure fluctuations. Damage can then be detected by comparing average values ​​with a predefined range. Ideally, the behavior of individual air springs within the vehicle can be compared with each other. This allows the identification of an air spring that exhibits increased air consumption under identical operating conditions.

[0036] It is therefore preferred to investigate whether the air consumption and / or the change in air consumption over time lies within a certain range, and to assume damage if the air consumption and / or the change in air consumption over time lies outside this range. Preferably, the air consumption of several air springs of a vehicle is determined, and defective air springs are identified based on their air consumption. In particular, it is determined whether the air consumption of an air spring exceeds a limit value.

[0037] According to a preferred embodiment of the method, the air consumption of an air spring system comprising a number of air springs is determined. Preferably, this is an air spring system in a rail vehicle, particularly in a multiple unit train. The air spring system need not necessarily consist solely of air springs. It can also include air distributors or its own switching elements. However, it is advantageous to include these switching elements in the method and determine their actuation times so that the air consumption of individual air springs can be determined. For example, the bogie of a multiple unit train can comprise several air springs. These can be monitored "en bloc" or individually. With en bloc monitoring, the spring air pressure of a total supply line can be measured; with individual monitoring, the spring air pressure of the individual air springs can be measured.

[0038] It is preferred that, in one embodiment of the method, measurement data on the spring air pressure and / or supply air pressure, and preferably also information on the flow resistance and / or actuation times of switching units for the air spring, are sent to a central unit. It is preferred that the air spring is assigned to a vehicle and the central unit is located outside the vehicle.

[0039] According to a preferred embodiment of the method, the procedure is repeated several times, particularly at predetermined times, and the air consumption is determined at different times. It is preferred that statistical characteristic values ​​for the air spring are derived from the various air consumption data. These can be determined, for example, from the spring air pressures or the air consumption at different times.

[0040] Preferably, vibrations are also measured during operation. This is preferably done using vibration sensors or acceleration sensors. The measured values ​​are then used to determine air consumption, particularly in conjunction with the spring air pressure. For example, if a vibration occurs during a journey, the spring air pressure changes briefly. It rises and then falls just as quickly, or vice versa. A damped oscillation pattern may also occur. If the vibration is then also measured, for example with an acceleration sensor, it is clear that the change in spring air pressure was not caused by a change in the air spring, but by the vibration.

[0041] According to a preferred embodiment of the method, the air consumption is determined in a static case where a control system for the air spring, in particular an actuation of the switching elements and the compressed air supply, keeps the volume (or deflection) of the air spring constant. This preferably occurs while a load acting on the air spring is changed, e.g., a change in the load of a vehicle suspended by this spring. It is preferred that, if the spring air pressure exceeds a predetermined maximum limit, a warning regarding overloading is issued. The method can thus also be used to detect overloading.

[0042] To validate the calculation, this can be done using different loads. A functional test could be performed as follows: In the static case, the volume of the air spring is deliberately manipulated by letting air in or out, and the relationship between air consumption and volume change is compared to a target value. Additionally, the tightness can be tested by deliberately deactivating the control system and measuring the pressure loss, as described above.

[0043] According to a preferred embodiment of the method, the air consumption is determined in a dynamic case where the volume in the air spring changes due to dynamic effects, in particular compression and rebound, e.g., during the driving operation of a vehicle suspended by this spring. In addition, the volume of the air spring is measured, and the air consumption is determined based on the measured volume. It is preferred that the volume of the air spring be determined based on its deflection.

[0044] The invention is explained in more detail below with reference to the accompanying figures and exemplary embodiments. The same components are designated with identical reference numerals in the various figures. The figures are generally not to scale. They show: Fig. 1 a device according to the invention for determining the air consumption of an air spring, Fig. 2 a block diagram of a method according to the invention, Fig. 3 a rail vehicle with an air spring system and a device according to the invention, Fig. 4 a track system with rail vehicles and a control center.

[0045] Fig. Figure 1 shows a device 10 according to the invention for determining the air consumption of an air spring 2 during operation, wherein the air spring 2 is connected to a compressed air supply 4 via a pipe 3 and the compressed air supply 4 to the air spring 2 is provided by means of switching elements 5 in the form of solenoid valves 5, a supply valve 5a and a vent valve 5b. It should be noted that the flow resistance S of the pipe 3 is known as a function of pressure differences.

[0046] The device 10 comprises an air spring measuring unit 11, a supply measuring unit 12, a switching measuring unit 13, a determination unit 14, and a data interface 15.

[0047] The air spring measuring unit 11 is used to measure the spring air pressure F in the air spring 2 during operation. The measured values ​​for the spring air pressure F are transmitted to the determining unit 14 (arrow).

[0048] The supply measuring unit 12 is used to measure the supply air pressure V of the compressed air supply 4 during operation. The measured values ​​for the supply air pressure V are transmitted to the determination unit 14 (arrow).

[0049] The switching measuring unit 13 is used to determine the actuation times A of the switching elements 5 during operation. The measured actuation times A are transmitted to the determination unit 14 (arrow).

[0050] Optionally, the deflection X or height of the air spring 2 (corresponding to its volume) can also be measured and transmitted to the determining unit 14 (dashed arrow). For this purpose, the distance between the top and bottom edges of the air spring is measured directly (e.g., with a laser measuring device or similar), or the change in deflection X or height during compression and rebound is measured using a linkage and angle sensor.

[0051] The determination unit serves to determine the air consumption L of the air spring 2 based on the determined flow resistance S, the spring air pressure F, the supply air pressure V and the actuation times A of the switching elements and, if necessary, also from the deflection X of the air spring 2.

[0052] The 5 data interface 15 is used to output information about air consumption L.

[0053] Fig. Figure 2 shows a block diagram of a method according to the invention for determining the air consumption L of an air spring 2 in operation with a device 10 according to Fig. 1.

[0054] In step I, the flow resistance S of the piping 3 from the compressed air supply 4 to the air spring 2 is specified as a function of the pressure difference. This can be determined experimentally or specified based on the geometric dimensions.

[0055] In step II, the spring air pressure F in the air spring 2, the supply air pressure V of the compressed air supply 4, and the deflection X of the air spring 2 are measured during operation, and the actuation times A of the switching elements 5 (solenoid valves 5) are determined during operation.

[0056] In step III, the air consumption L of the air spring 2 is determined based on the determined flow resistance S, the spring air pressure F, the supply air pressure V, the deflection X of the spring and the actuation times A of the switching elements 5 (using physical pressure equations).

[0057] The deflection of the spring can preferably be disregarded and neither measured nor used for the determination.

[0058] The information about air consumption L is then displayed.

[0059] Fig. Figure 3 shows a rail vehicle 1 with an air spring system 6 and a device 10 according to the invention. In this example, the air springs 2 of the individual bogies of the rail vehicle are monitored. The air spring system 6 consists of the air springs 2 and the control units for the air springs (boxes). Solenoid valves 5 can also be arranged in the boxes, in which case the connecting lines would be cables; however, only distributors may be present, in which case the lines would be pressure lines. Basically, the air spring system 6 could consist of several systems according to Fig. 1. Device 10 would then have correspondingly more measuring units.

[0060] Fig.Figure 4 shows a track system with rail vehicles 1 and a control unit 7. The rail vehicles 1 travel through this track system and are all in contact with the control unit 7. They transmit their measurement data on the spring air pressure F and / or supply air pressure V, and preferably also information on the flow resistance S and / or actuation times A of switching units for the air spring 2, to the control unit 7. The control unit 7 can thus detect faults in the air springs 2 at an early stage and initiate appropriate measures.

[0061] Finally, it should be noted once again that the invention described in detail above merely represents exemplary embodiments, which can be modified in various ways by a person skilled in the art without departing from the scope of the invention. Furthermore, the use of the indefinite articles "a" or "an" does not preclude the possibility that the features in question may be present multiple times. Likewise, terms such as "unit" do not preclude the possibility that the components in question consist of several interacting sub-components, which may also be spatially distributed. The term "a number" should be read as "at least one." Regardless of the grammatical gender of a particular term, persons of male, female, or other gender identities are included. Reference symbol list 1 rail vehicle 2 air springs 3 Piping 4 Compressed air supply 5 Switching element / solenoid valve 5a Supply valve 5b Vent valve 6 Air suspension system 7 Central 10 Device 11 Air spring measuring unit 12 Supply measuring unit 13 Switching measuring unit 14 Unit of determination 15 Data interface A control time F Spring-air pressure L Air consumption S Flow resistance V Supply air pressure X deflection

Claims

[1] Method for determining the air consumption (L) of an air spring (2) during operation, wherein the air spring (2) is connected to a compressed air supply (4) via a piping (3) and the compressed air supply (4) to the air spring (2) is provided by means of switching elements (5), the method comprising the steps: - Determining or specifying a flow resistance (S) of the piping (3) as a function of the pressure difference, - Measuring a spring air pressure (F) in the air spring (2) during operation, - Measuring the supply air pressure (V) of the compressed air supply (4) during operation, - Determining the actuation times (A) of the switching elements (5) during operation, - Determining the air consumption (L) of the air spring (2) based on the determined flow resistance (S), the spring air pressure (F), the supply air pressure (V) and the actuation times (A) of the switching elements (5), - Outputting information about air consumption (L). [2] Method according to claim 1, wherein the switching elements (5) are controlled valves, preferably solenoid valves (5). [3] Method according to one of the preceding claims, wherein geometric data on the diameter and structure of the piping (3) are provided to determine the flow resistance (S), or measurements of the flow resistance (S) are carried out in operation at different pressures. [4] Method according to one of the preceding claims, wherein damage to the air spring (2) is detected from the air consumption (L) of the air spring (2), in particular from a change in the air consumption (L) over time, preferably wherein it is investigated whether the air consumption (L) and / or the change in the air consumption (L) over time is within a range of values ​​and damage is assumed if the air consumption (L) and / or the change in the air consumption (L) over time is outside this range of values. [5] Method according to one of the preceding claims, wherein the air consumption (L) of an air spring system (6) comprising a number of air springs (2) is determined, preferably an air spring system (6) in a rail vehicle (1), in particular a multiple unit train. [6] Method according to one of the preceding claims, wherein measurement data on spring air pressure (F) and / or supply air pressure (V) and preferably also information on flow resistance (S) and / or actuation times (A) of switching units for the air spring (2) are sent to a central unit (7), preferably wherein the air spring (2) is assigned to a vehicle and the central unit (7) is outside the vehicle. [7] Method according to one of the preceding claims, wherein the method is repeated several times, in particular at predetermined times, and the air consumption (L) is determined at different times, preferably wherein statistical characteristic values ​​for the air spring (2) are determined from the different information on the air consumption (L). [8] Method according to one of the preceding claims, wherein the air consumption (L) is determined in a static case in which a control of the air spring (2) keeps the volume of the air spring (2) constant, preferably while a load acting on the air spring (2) is changed, [9] Method according to one of the preceding claims, wherein the air consumption (L) is determined in a dynamic case in which the volume in the air spring (2) changes due to dynamic effects, in particular compression and rebound, wherein the volume of the air spring (2) is additionally measured and the air consumption (L) is determined based on the measured volume, preferably wherein the volume of the air spring (2) is determined based on its displacement (X). [10] Device (10) for determining the air consumption (L) of an air spring (2) during operation, wherein the air spring (2) is connected to a compressed air supply (4) via a pipe (3) and the compressed air supply (4) to the air spring (2) is provided by means of switching elements (5), the device (10) comprising: - an air spring measuring unit (11) designed to measure a spring air pressure (F) in the air spring (2) during operation, - a supply measuring unit (12), designed to measure a supply air pressure (V) of the compressed air supply (4) during operation, - a switching measuring unit (13) designed to determine the actuation times (A) of the switching elements (5) during operation, - a determination unit (14) designed to determine the air consumption (L) of the air spring (2) based on the determined flow resistance (S), the spring air pressure (F), the supply air pressure (V) and the actuation times (A) of the switching elements (5), - a data interface (15) designed to output information about air consumption (L). [11] Vehicle, in particular a rail vehicle (1), comprising an air spring system (6) and a device (10) according to claim 10 designed for determining the air consumption (L) of the air spring system (6).

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