Device and method for hydrogen measurement in a rolling bearing arrangement

Abstract

Rolling bearing arrangement (1), with a number of rolling elements (2), a bearing component (3) providing a raceway (8) for the rolling elements (2), and a receiving component (4) in which the bearing component (3) is received in such a way that hydrogen can be enclosed between the bearing component (3) and the receiving component (4), wherein the receiving component (4) is partially designed as a pressure-sensitive membrane (12), and with a sensor (10) provided for detecting a deformation of the membrane (12).

Description

[0001] The invention relates to a device comprising at least one rolling bearing, which is designed to measure the hydrogen concentration, in particular the concentration of molecular hydrogen, in the rolling bearing. Furthermore, the invention relates to a measuring method that can be carried out using such a device, i.e., a rolling bearing arrangement.

[0002] A measurement method for detecting hydrogen in a rolling bearing assembly is known in principle from WO 2013 / 012364 A1. This method is intended to be used in a rolling bearing designed as a roller bearing and enables the measurement of a hydrogen concentration in a rolling bearing component that is subjected, among other things, to Hertzian stress. A sensor, which can be a pressure sensor, is provided for the measurement. The sensor can be arranged in a cavity. The measurement assumes that hydrogen in atomic form penetrates metal.

[0003] One possible method for measuring the hydrogen content absorbed by permeation into a workpiece in the form of hydrogen atoms is disclosed, for example, in EP 2 912 452 B1. The method utilizes a measuring arrangement with a collecting element that is to be connected to the workpiece. A mixing chamber is connected between the collecting element and the workpiece.

[0004] WO 2016 / 042309 A1 describes a membrane made of a two-dimensional material which conducts protons and is said to be suitable for use in a hydrogen sensor.

[0005] Another method for measuring the hydrogen content in a sample is disclosed in EP 2 863 218 B1. This method uses, among other things, a thermal desorption chamber. In addition to gas originating from the sample under investigation, calibration gas can also be supplied to the thermal desorption chamber.

[0006] EP 2 013 616 B1 discloses a method for detecting hydrogen in steel. In this method, the hydrogen present in the steel is at least partially converted into vanadium, niobium, or tantalum by diffusion. Based on the quantitative determination of the hydrogen concentration in this material, i.e., vanadium, niobium, or tantalum, the hydrogen concentration in the steel can be determined.

[0007] EP 1 238 247 B1 describes a method for measuring hydrogen diffusion through a metallurgical structure. This method includes, among other things, the use of a metering thermocouple.

[0008] A method and device for measuring hydrogen in a rolling bearing assembly, which is suitable, among other things, for use in a wind turbine, are disclosed in the subsequently published DE 10 2018 115 552 A1. In this case, a cavity in which hydrogen accumulates during operation of the rolling bearing assembly, thus leading to an increase in pressure, can be vented by means of a vent valve designed as an externally controllable valve.

[0009] The invention is based on the object of providing possibilities for hydrogen measurement that are more advanced than the prior art, whereby both a simple, compact and at the same time robust system design and a good possibility for metrological evaluation should be provided.

[0010] This object is achieved according to the invention by a rolling bearing arrangement having the features of claim 1. The object is also achieved by a method for hydrogen measurement according to claim 8. Embodiments and advantages of the invention explained below in connection with the measuring method also apply mutatis mutandis to the device, i.e. the rolling bearing arrangement, and vice versa.

[0011] The rolling bearing assembly comprises a number of rolling elements, a bearing component, in particular a bearing ring or a bearing disk, which provides a raceway for the rolling elements, and a receiving component, for example in the form of a bearing disk receptacle, in which the bearing component is received. The receptacle of the bearing component in the receiving component is designed such that hydrogen, which forms during operation of the rolling bearing component, is enclosed between the bearing component and the receiving component. The receiving component is partially designed as a pressure-sensitive membrane that responds to molecular hydrogen formed by the recombination of atomic hydrogen. A further component of the rolling bearing assembly is a sensor provided for detecting deformation of the membrane.

[0012] The invention is based on the consideration that hydrogen can be released during operation of components in a rolling bearing arrangement or other components subject to rolling stresses, such as gears in a transmission. It is assumed that hydrogen can be released particularly from lubricant systems, whereby an oil or grease formulation may also contain water contamination. If diffusible hydrogen formed in this way is absorbed by a rolling bearing component or other machine component, this increases the risk of so-called white etching cracks (WECs), according to current theories. Atomic hydrogen escaping from steel, in this case particularly rolling bearing steel, recombines very quickly into molecular hydrogen.

[0013] Against this background, detection of hydrogen formation in rolling bearing steel appears appropriate for various applications, such as wind turbines or paper machines. Depending on the design, detection can be carried out using the rolling bearing assembly either in real time or after an operating phase. In both cases, there is a clear correlation between the deformation of the membrane and the hydrogen formed during operation. In the latter case, it is particularly possible to determine whether a critical hydrogen concentration existed at any time during the operation of the rolling bearing assembly, including a bearing.

[0014] In a preferred embodiment, the diaphragm is formed directly by the receiving component, i.e., it is integrally connected to the remaining receiving component. The receiving component thus has, on the one hand, a mechanical function, supporting the bearing component, and, on the other hand, a metrological function in the form of the diaphragm.

[0015] The rolling bearing arrangement can generally be designed as a radial bearing, an axial bearing, or a bearing arrangement suitable for absorbing both radial and axial forces. In all cases, the rolling elements of the rolling bearing arrangement can be balls or roller-shaped rolling elements, such as cylindrical rollers, barrel rollers, tapered rollers, or needle rollers.

[0016] The receiving component forming the diaphragm can be either a stationary or rotating component of the rolling bearing assembly. In the latter case, rotating measurement components, if real-time pressure measurement is intended, can be coupled, for example, via sliding contacts or contactlessly, for example inductively, to non-rotating components used for signal and energy transmission.

[0017] The thickness of the bearing component on whose surface hydrogen can collect must be measured in the axial direction in the case of an axial bearing and in the radial direction in the case of a radial bearing. In both cases, the minimum thickness of the bearing component is typically less than the rolling element diameter. The diaphragm, with which a pressure build-up can be detected, can be placed in front of a surface of the bearing component which is directly opposite the raceway for the rolling elements provided by the bearing component. Despite the mechanical weakening of the receiving component by the diaphragm, the receiving component is sufficiently stable not to be deformed by mechanical loads introduced into the bearing component via the rolling elements to such an extent that the diaphragm falsely indicates a pressure change.

[0018] In designs where a slight but measurable deformation of the diaphragm occurs due to the rolling elements, this mechanically induced deformation is superimposed on the deformation of the diaphragm caused by the pressure buildup, i.e., by molecular hydrogen. The mechanically induced deformation represents an oscillating, particularly approximately sinusoidal, signal, which is subtracted from the total signal measured and created by superposition.

[0019] An eddy current sensor, for example, is suitable as a sensor for detecting membrane deformation. Other types of sensors, such as optical sensors, are also generally suitable for detecting membrane deformation. Tactile (meaning mechanical) sensors, as well as capacitive and inductive sensors, are also suitable for detecting membrane deformation.

[0020] Compared to the bearing component held by the receiving component, on which the rolling elements roll, the diaphragm has a thin-walled design. For example, the thickness of the diaphragm corresponds to at least 3% and a maximum of 25% of the minimum thickness of the aforementioned bearing component. The diaphragm thickness is preferably at least 0.01% and a maximum of 5% of the diaphragm diameter. The diaphragm is preferably circular.

[0021] The space in which molecular hydrogen accumulates, leading to deformation of the membrane, is small compared to the installation space occupied by the entire rolling bearing assembly. Even a roughness-induced, gap-like cavity between a surface of the bearing component and a surface of the receiving component is sufficient for the recombination of hydrogen and the buildup of pressure within the rolling bearing assembly. A large surface area of ​​the cavity compared to its volume is particularly advantageous. This allows even small amounts of hydrogen to be detected. By integrating the membrane into the receiving component, any dead spaces, which would impair the sensitivity of the hydrogen detection device, are avoided.

[0022] To seal the cavity in which hydrogen can accumulate, a soldered connection can be provided between the bearing component and the receiving component. Furthermore, an insulating film made of plastic, for example, polyimide, can optionally be arranged between the receiving component and the bearing component. Such films are available on the market, for example, under the Kapton brand. The insulating film acts as a solder barrier during the soldering process. Furthermore, the insulating film can be used to set a defined distance between the bearing component and the receiving component if this is intended to conduct gas – possibly in defined channels. Another positive property of the insulating film is its damping properties. The insulating film is dimensioned and incorporated into the rolling bearing assembly in such a way that it does not negatively affect the mechanical precision of the rolling bearing assembly.

[0023] According to a possible refinement, the rolling bearing assembly has a vent opening. This vent opening, like the membrane, borders the volume within which hydrogen can accumulate. A vent valve arranged in the vent opening is preferably externally controllable and, at the same time, designed in such a way that it contributes only minimally to the increase in said volume.

[0024] Within the scope of the method for hydrogen measurement according to the invention, hydrogen generated during operation of the rolling bearing assembly is collected in a sealed volume formed between the bearing component and the receiving component. The hydrogen generated leads to the deformation of the pressure-sensitive membrane integrated into the receiving component, with the deformation of the membrane being measured.

[0025] The deformation of the diaphragm, which is caused by the accumulation of hydrogen in the volume, particularly in the form of a gap-like cavity, can be elastoplastic. This means that any deformation that has occurred remains for an extended period of time, even if the rolling bearing assembly is disassembled. After disassembly of the rolling bearing assembly, the permanent deformation of the diaphragm compared to the initial state can be determined, for example, using simple length measurement technology. From this, the pressure that prevailed due to the hydrogen generated during operation of the rolling bearing can be deduced. The pressure thus indirectly determined, in turn, allows a conclusion to be drawn about the amount of hydrogen generated. During operation of the rolling bearing assembly, the hydrogen generated remains almost entirely within the cavity formed between the bearing component and the receiving component, since recombined hydrogen hardly diffuses through the diaphragm.

[0026] If no separate venting hole is available, a simple way to vent the membrane is to drill into it. Following this destructive process, it is possible to determine the extent to which the membrane has recovered elastically.

[0027] As an alternative to subsequent determination of the hydrogen generated during operation of the rolling bearing assembly, in situ measurement is also possible by continuously measuring the geometry of the membrane. Such measurement can be achieved, for example, using strain gauges on the membrane.

[0028] Two exemplary embodiments of the invention are explained in more detail below with reference to a drawing. In each case, in a simplified representation: Fig. 1 a rolling bearing arrangement in the form of an axial bearing with integrated device for hydrogen measurement, Fig. 2 a spherical roller bearing with a device for hydrogen measurement.

[0029] Unless otherwise stated, the following explanations refer to both embodiments. Corresponding or essentially equivalent parts are identified by the same reference numerals in the same figures.

[0030] A rolling bearing arrangement, identified overall by the reference numeral 1, comprises a number of rolling elements 2, which in the embodiment according to Fig. 1 as cylindrical rollers and in the embodiment according to Fig. 2 are designed as barrel rollers. In the rolling bearing arrangement 1 according to Fig. 1 is an axial bearing, in which the rolling bearing arrangement 1 according to Fig. 2 is a spherical roller bearing.

[0031] The rolling elements 2 roll on a bearing component 3, which in the case of Fig. 1 around a bearing disc and in the case of Fig. 2 is a bearing ring. In both embodiments, the bearing component 3 is a non-rotating component of the rolling bearing assembly 1.

[0032] The bearing component 3 is held in a receiving component 4, which in the case of Fig. 1 is also referred to as a bearing disc holder. Compared to the holder component 4, the bearing component 3 is a relatively thin-walled part. The thickness of the bearing component 3 is designated DL. In the case of Fig. 2, the bearing component 3 has a non-uniform thickness. The thickness DL is the minimum thickness in this case and is to be measured in the center of the bearing ring 3, i.e. in the center plane between the two rows of rolling elements, designated 16 and 17. In addition to the bearing ring 3, namely the rolling bearing outer ring, Fig. 2, an inner ring 15 can be seen as an additional bearing ring. The bearing rings 3, 15 can be constructed in one or more parts.

[0033] The Fig. 1 The width of the bearing disc 3 designated BL is to be measured in the radial direction of the rolling bearing arrangement 1. In contrast, in the arrangement according to Fig. 2 measure the width of the bearing rings 3, 15 in the axial direction of the rolling bearing arrangement 1.

[0034] The bearing component 3 is inserted in a gas-tight manner into the receiving component 4. For this purpose, a soldered connection 5 is made between the bearing component 3 and the receiving component 4. The soldered connections 5 close off a gap-shaped cavity, which is delimited, among other things, by a surface of the bearing component 3 designated by 7. The surface 7, which in the case of Fig. 1 a ring disc shape and in the case of Fig. 2 has a cylindrical shape, is located directly opposite the raceway designated 8, on which the rolling elements 2 roll. The roughness of the surface 7 is greater than the roughness of the raceway 8. The raceway 8 has in the case of Fig. 1 a ring disc shape and in the case of Fig. 2 a curved shape.

[0035] Adjacent to the surface 7 is a measuring arrangement which serves to detect hydrogen formed in the rolling bearing arrangement 1 and is designated overall by 9. Part of the measuring arrangement 9 is a membrane 12 which is formed directly by the receiving component 4. The membrane 12 is not only thinner-walled than the rest of the receiving component 4, but also several times thinner-walled than the bearing component 3. The thickness of the membrane 12 is designated DM. The diameter of the rolling elements 2, designated DW, is in the exemplary embodiments a multiple of the thickness DL of the bearing component 3. The membrane thickness DM is more than 0.01%, but less than 5% of the diameter designated D 12 designated diameter of the membrane 12.

[0036] Forces introduced into the bearing component 3 via the rolling elements 2 do not lead to deformation of the bearing component 3, or only to a negligible extent. Accordingly, the shape of the diaphragm 12 does not depend on the load on the rolling elements 2. The purpose of the diaphragm 12 is to detect a change in pressure in the minimal gap formed between the receiving component 4 and the bearing component 3. An increase in pressure occurs due to the hydrogen generated at the bearing component 3.

[0037] Such an increase in pressure leads to a deformation of the membrane 12, whereby Fig. 2 a deformed contour 13 of the membrane 12 is indicated by dashed lines. A device arranged according to Fig. One existing sensor 10 is designed as an eddy current sensor. This sensor 10 can detect any deformation of the membrane 12 in real time.

[0038] In Fig. 2 shows a vent opening 11 which ends at the outer surface of the bearing ring 3 of the spherical roller bearing, designated overall by 14. The vent opening 11 allows ventilation of the very shallow cavity, which is closed, among other things, by the soldered joints 5. A minimal gap between the bearing component 3 and the receiving component 4 is partially filled by a plastic film 6 made of polyimide. The polyimide film 6 functions as a solder barrier. A vent valve (not shown), with which the vent opening 11 can be opened and closed, is located close to the surface 7 and has a small dead volume, so that the volume formed between the bearing component 3 and the receiving component 4, in which hydrogen can collect, is kept small overall.

[0039] The arrangement according to Fig. 2 is in contrast to the arrangement according to Fig.1 is not intended for in situ measurement, but for the subsequent determination of hydrogen produced. After atomic and then molecular hydrogen has initially formed during operation of the rolling bearing assembly 1 and has led to the deformation of the diaphragm 12, as indicated by the deformed contour 13, the vent opening 11 is opened. This leads to a partial re-deformation of the diaphragm 12, whereby the original state is not regained. The remaining plastic deformation of the diaphragm 12 allows a conclusion to be drawn about the maximum pressure during operation of the rolling bearing assembly 1. In a destructive manner not shown, instead of pressure reduction via the vent opening 11, produced gas could also be discharged by drilling into the diaphragm 12. In both cases, the permanent deformation of the diaphragm 12 can be determined using a length measuring device. List of reference symbols 1 rolling bearing arrangement 2 rolling elements, cylindrical roller, barrel roller 3 Bearing component, bearing disc, bearing ring 4 Mounting component 5 Solder connection 6 Plastic film, insulation film 7 Surface of the bearing component 8 Bearing component raceway 9 Measuring arrangement 10 Sensor, eddy current sensor 11 Ventilation opening 12 Membran 13 deformed contour of the membrane 14 rolling bearings, spherical roller bearings 15 inner ring 16 rolling element rows 17 rolling element row BL Width of the bearing component DL Thickness of the bearing component DM thickness of the membrane DW rolling element diameter D 12 Diameter of the membrane

Claims

[1] Rolling bearing arrangement (1), with a number of rolling elements (2), a bearing component (3) providing a raceway (8) for the rolling elements (2), and a receiving component (4) in which the bearing component (3) is received in such a way that hydrogen can be enclosed between the bearing component (3) and the receiving component (4), wherein the receiving component (4) is partially designed as a pressure-sensitive membrane (12), and with a sensor (10) provided for detecting a deformation of the membrane (12). [2] Rolling bearing arrangement (1) according to claim 1, characterized by that the membrane (12) borders on a surface (7) of the bearing component (3) opposite the raceway (8). [3] Rolling bearing arrangement (1) according to claim 1 or 2, characterized by that an eddy current sensor is provided as the sensor (10). [4] Rolling bearing arrangement (1) according to one of claims 1 to 3, characterized bya vent opening (11) provided for discharging hydrogen located between the receiving component (4) and the bearing component (3). [5] Rolling bearing arrangement (1) according to one of claims 1 to 4, characterized by that the thickness (DM) of the membrane (12) is at least 0.01% and a maximum of 5% of the diameter (D 12 ) of the membrane (12). [6] Rolling bearing arrangement (1) according to one of claims 1 to 5, characterized by that the bearing component (3) is sealed from the receiving component (4) by a soldered connection (5). [7] Rolling bearing arrangement (1) according to one of claims 1 to 6, characterized by an insulating film (6) made of plastic inserted between the receiving component (4) and the bearing component (3). [8] Method for measuring hydrogen in a rolling bearing arrangement (1) which comprises a number of rolling elements (2), an annular or disc-shaped bearing component (3) providing a raceway (8) for the rolling elements (2), and a receiving component (4) in which the bearing component (3) is received, wherein hydrogen generated during operation of the rolling bearing arrangement (1) is collected in a sealed volume formed between the bearing component (3) and the receiving component (4) and leads to the deformation of a pressure-sensitive membrane (12) integrated in the receiving component (4), wherein the deformation of the membrane (12) is measured. [9] Method according to claim 8, characterized by that the deformation of the membrane (12) is measured during the ongoing operation of the rolling bearing arrangement (1). [10] Method according to claim 8, characterized bythat a plastic deformation of the membrane (12) following an operating phase of the rolling bearing arrangement (1), in particular after disassembly of the rolling bearing arrangement (1), is determined by measurement.

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