Self-healing sliding bearing

Abstract

The present invention relates to a method for operating a sliding bearing, comprising the following steps: obtaining a first rotational speed at which a lubrication state transition occurs or at which friction is minimized in the sliding bearing; comparing the first rotational speed with a threshold value; and when the first rotational speed exceeds the threshold value, causing a self-healing wear effect to occur in the operation of the sliding bearing.

Description

Field of Technology

[0001] The present invention relates to a method for operating a hydrodynamic sliding bearing and a controller for implementing the method thereon. Background Art

[0002] Hydrodynamic sliding bearings can operate in different lubrication states. Possible lubrication states are: boundary friction, mixed friction or sliding friction. The transition between the friction states is not distinct. Ideally, a hydrodynamic sliding bearing operates only in sliding friction. Here, the sliding surfaces are completely separated by a load-bearing lubricating film. In this operating state, no wear occurs. However, in many applications, for example in wind power transmissions, it is not possible to operate only in sliding friction. If boundary friction or mixed friction exists, the bearing wears and eventually fails in the later stages of wear.

[0003] The so-called self-healing wear effect is known from the prior art. For example, the self-healing wear effect is described in "Schnell laufende Verbrennungsmaschinen" (H. Ricardo; Springer-Verlag, Berlin, 1926) ["High-speed Internal Combustion Engines" (H. Ricardo; Springer-Verlag, Berlin, 1926)]. By means of the self-healing wear effect, the running surfaces of a damaged sliding bearing can be smoothed. For this purpose, a suitable operating point with mixed friction is approached purposefully. The mixed friction causes the previously present roughness to be levelled again. So far, the self-healing wear effect has only been achievable under laboratory conditions.

[0004] The lubrication state of a sliding bearing can be determined based on structure-borne sound signals detected by one or more acoustic emission sensors (Acoustic Emission Sensoren). The corresponding methods are described in "Classification of Journal Bearing Friction States based on Acoustic Emission Signals" (N. Mokhtari, C. Guhmann; TM - Technisches Messen, Vol. 85, Issue 6, 2018) ["Classification of Journal Bearing Friction States based on Acoustic Emission Signals" (N. Mokhtari, C. Guhmann; TM - Technical Measurement, Vol. 85, No. 6, 2018)] and "Approach for the Migration of Hydrodynamic Journal Bearings based on Acoustic Emission Feature Change" (N. Mokhtari, C. Guhmann, S. Novolski; IEEE International Conference on Prognostics and Health Management (ICPHM), 2018) ["Approach for the Migration of Hydrodynamic Journal Bearings based on Acoustic Emission Feature Change" (N. Mokhtari, C. Guhmann, S. Novolski; IEEE International Conference on Prognostics and Health Management (ICPHM), 2018)]. A method for deriving the Stribeck curve from the signals of acoustic emission sensors is known from "Vibration Signal Analysis for the Life-time-Prediction and Failure Detection of Future Turbofan Components" (N. Mokhtari, M. Riskowski, C. Guhmann; Technische Mechanik 37, 2017) ["Vibration Signal Analysis for the Life-time-Prediction and Failure Detection of Future Turbofan Components" (N. Mokhtari, M. Riskowski, C. Guhmann; Engineering Mechanics 37, 2017)]. Summary of the Invention

[0005] The object of the present invention is to improve the operational reliability of a sliding bearing and to prevent premature failure due to damage. This object is achieved by a method for operating a sliding bearing according to the invention and a controller according to the invention.

[0006] The method according to the invention enables the targeted use of the self-healing wear effect in a sliding bearing during operation.

[0007] The invention is based on the following insight: The use of the self-healing wear effect in a drive during operation requires valid knowledge about the current state of the sliding bearing. The rotational speed that occurs when the lubrication state of the sliding bearing changes is used as an indication of the state. Accordingly, the method according to the invention provides that, as one of two alternatives, a first rotational speed of the sliding bearing is determined, at which a change in the lubrication state occurs in the sliding bearing or in the bearing clearance of the sliding bearing.

[0008] The rotational speed of the sliding bearing refers to the relative rotational speed of two sliding surfaces of the sliding bearing that can twist relative to each other. A bearing clearance extends between the sliding surfaces, in which boundary friction, mixed friction, or fluid friction occurs depending on the operating point. These three types of friction characterize the lubrication state of the sliding bearing. A change in the lubrication state accordingly corresponds to a change between boundary friction and mixed friction or between mixed friction and fluid friction. Thus, a change from boundary friction to mixed friction, from mixed friction to boundary friction, from mixed friction to fluid friction, and / or from fluid friction to mixed friction can occur.

[0009] As mentioned at the beginning, the lubrication state or a change in the lubrication state can be determined by methods known from the prior art. For this purpose, in particular, acoustic emission sensors can be used.

[0010] Alternatively, the first rotational speed characterizes the operating point with the least friction in the sliding bearing, i.e., in its bearing clearance. This means that the friction in the sliding bearing is greater at any other rotational speed than at the first rotational speed. Friction refers to the frictional torque that causes the sliding bearing to resist the relative rotation of the sliding surfaces due to the friction occurring in the bearing clearance.

[0011] Preferably, the mentioned operating point is determined according to the Stribeck curve. As described above, the method for determining the Stribeck curve is known from the prior art. The Stribeck curve assigns to each rotational speed of the sliding bearing the corresponding friction occurring in the bearing. The rotational speed with the least friction can be determined according to the Stribeck curve.

[0012] The higher the first rotational speed, the worse the state of the sliding bearing. In particular, rough sliding surfaces result in a higher first rotational speed. Therefore, the first rotational speed is an indication of wear or damage to the sliding bearing. Accordingly, according to the invention, the first rotational speed is used as an indication of possible wear or damage to the sliding bearing. A threshold value compared with the first rotational speed serves as a criterion for evaluating the state of the sliding bearing.

[0013] If the first rotational speed exceeds a threshold value, it can be considered that the sliding bearing is worn or damaged. In this case, according to the method of the present invention, it is provided that the sliding bearing is regenerated by self-repairing wear. Thus, the bearing operates in such a way that a self-repairing wear effect occurs, i.e., the bearing is in an operating state in which a self-repairing wear effect occurs. Here, other operating states are avoided. The occurrence of mixed friction in the bearing clearance is characteristic of this operating state.

[0014] In a preferred refinement of the method, a second rotational speed is ascertained. This preferably takes place after the above-mentioned method step. Like the first rotational speed, the second rotational speed is characterized by a change in the lubrication state of the sliding bearing or a minimum of friction in the sliding bearing. Thus, the first rotational speed and the second rotational speed are ascertained in the same way. The above-described embodiments regarding the ascertainment of the first rotational speed apply mutatis mutandis to the second rotational speed.

[0015] The second rotational speed is used to check the effect of self-repair. The lower the second rotational speed, the more successful the self-repair.

[0016] Preferably, the second rotational speed is compared with the first rotational speed. For example, the difference between the first rotational speed and the second rotational speed can be calculated. The greater this difference, the more successful the self-repair.

[0017] Alternatively, the second rotational speed can be compared with a predetermined reference rotational speed. The reference rotational speed can be, for example, the rotational speed at which the lubrication state of an undamaged reference bearing changes or the rotational speed at which the friction in the reference bearing is minimal. Preferably, a sliding bearing in a new state serves as the reference bearing. In particular, it can be the above-mentioned sliding bearing in a new state. The reference rotational speed is then ascertained before installing the sliding bearing.

[0018] Depending on the result of the comparison, various measures can be taken. If the comparison leads to the conclusion that self-repair has been successful, the sliding bearing can continue to operate without change. Conversely, if the self-repair is not successful, a warning is issued, for example, in order to replace the sliding bearing in a timely manner. It is also possible to operate the sliding bearing in such a way as to avoid particular operating states that load the sliding bearing particularly highly.

[0019] A controller according to the present invention implements the method according to the present invention or a preferred refinement thereof. The data processing device is referred to as a controller. Description of the Drawings

[0020] Preferred embodiments of the present invention are shown in Figure 1 as follows:

[0021] Figure 1 Two Stribeck curves are shown in detail. Detailed Description of the Invention

[0022] Figure 1The first Stribeck curve 101 and the second Stribeck curve 103 are shown. Three operating states, namely boundary friction 105, mixed friction 107, and fluid friction 109, are assigned to the first Stribeck curve 101. At the so-called separation point B, the transition from mixed friction 107 to fluid friction 109 occurs. At point A, the friction is minimal.

[0023] Through self-repairing wear, the first Stribeck curve 101 is transformed into the second Stribeck curve. The second Stribeck curve 103 is shifted towards the low rotational speed direction or to the left relative to the first Stribeck curve. Accordingly, points A and B also shift. The more they shift, that is, the greater the distance between the corresponding points A and B of the first Stribeck curve 101 and the second Stribeck curve 103, the more successful the self-repair is. The distance between the corresponding points A and B of the two Stribeck curves 101, 103 can thus be used as an indication of the success of self-repair.

[0024] List of reference numerals

[0025] 101 First Stribeck curve

[0026] 103 Second Stribeck curve

[0027] 105 Boundary friction

[0028] 107 Mixed friction

[0029] 109 Fluid friction

Claims

1. Method for operating a sliding bearing; the method having the following steps: - ascertaining a first rotational speed at which a change in the lubrication state occurs or at which friction in the sliding bearing is minimal; - comparing the first rotational speed with a threshold value; and - When the rotational speed exceeds the threshold, the bearing is in an operating state where mixed friction occurs, wherein the sliding bearing is regenerated by self-healing wear, wherein if the first rotational speed exceeds the threshold value, the sliding bearing is considered to be worn or damaged, and wherein the first rotational speed serves as an indication of possible wear or damage to the sliding bearing.

2. Method according to claim 1; the method having the following steps: - ascertaining a second rotational speed at which a change in the lubrication state of the sliding bearing occurs or at which friction in the sliding bearing is minimal; and - comparing the first rotational speed and the second rotational speed.

3. Controller on which the method according to any one of the preceding claims is implemented.

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