Method and device for monitoring a bearing clearance of roller bearings
a technology of roller bearings and clearances, which is applied in the direction of machines/engines, instruments, force/torque/work measurement apparatus, etc., can solve the problems of increasing distance, affecting the accuracy of measurement, so as to eliminate the influence of axial run-out and concentricity. , the effect of eliminating the influence of distance values
Active Publication Date: 2021-04-29
SCHAEFFLER MONITORING SERVICES GMBH
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Benefits of technology
[0021]It is particularly important that a statement about the bearing clearance is made not on the basis of an absolute, possibly also averaged distance measurement, but rather solely on the basis of the change in the distance delta in the temporal profile in at least two defined load states. This is achieved in particular by a relative measurement. The essential advantage in this case is that the influence of the varying load states for the bearing clearance specifically does not have to be sensed and calculated in a complex manner.
[0029]This is due to the fact that more rolling bodies contribute in the case of a small bearing clearance than in the case of a large bearing clearance. The bearing rigidity is therefore higher in the case of a small bearing clearance than in the case of a large bearing clearance. A different distance delta accordingly likewise thus results in the case of an increasing load depending on the bearing clearance.
[0048]This has the major advantage that interfering influences such as axial run-out defects and concentricity defects are reduced. If an axial run-out defect or concentricity defect were to be a simple sinusoidal profile, the distorting influence would be eliminated by such evaluation. Since however an often sinusoidal profile is overlaid with random deviations (for example wavy or local elevations / indentations), a periodic distance change likewise forms in the simultaneous mean value during one rotation (360°). The amplitude of this distance change is however much smaller than that of the individual distance measurements with the individual distance sensors. The periodicity, that is to say frequency of the distance change, is given by the product of the rotational frequency of the shaft and the number of sensors.
[0055]If constant load states are present over a plurality of revolutions, there is furthermore provision, in one preferred development, to eliminate changes in the distance values caused by fabrication deviations by forming a floating mean value in order to (exactly) determine the present distance value caused by the current load state and to determine the distance delta to other load states. To this end, the periodic nature of the distance signal is preferably utilized. Since the rotational speed is able to be determined from the signal as described above, it is possible to define the region for the floating mean as n times a rotor revolution, wherein n is greater than or equal to 1 and is preferably 2 and is at most 10. It is thereby possible to completely eliminate the axial run-out influence and concentricity influence in the measurement. This is due to the fact that the mean value of the axial run-out profile and concentricity profile is constant over one rotor revolution or multiples thereof.
Problems solved by technology
If the bearing clearance increases (when it is positive) or the bearing preload is reduced due to said mechanisms, this leads, in the medium or long term, to consequential damage to the bearing system, as far as failure thereof.
It is however not possible to use this method to monitor wear, setting or releasing.
This is due to the fact that wear on the bearing having the adjustment device leads for example to an increase in distance, and wear on the opposing bearing leads to a reduction in distance.
The measurement is additionally overlaid with considerable temperature effects resulting from normal operation.
Such a device is therefore not suitable for monitoring the condition of a bearing clearance, but rather only for compensating thermal expansions.
It is also the case here that wear of the raceways and / or rolling bodies is not able to be detected unambiguously, since the measurement is distorted, on the one hand, by the temperature effects.
Both of the abovementioned approaches thus target the adjustment or constant maintenance of the operating clearance by compensating temperature influences, but are not however able to detect long-term changes to the preload or the bearing clearance caused by wear, setting or releasing.
However, these measurement methods require a multiplicity of sensors and complex preliminary calculations in order to determine the correlations.
One common feature of the cited prior art is that load changes during operation may greatly distort the control and / or measurement result, since such load changes likewise lead to distance changes.
These may be axial run-out and concentricity defects, flatness and roundness deviations or surface defects.
If this is not taken into account in the evaluation, this may lead to extremely large scatter in the measurement result and call it into question.
Method used
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>[0069]FIG. 1 illustrates a bearing unit 2 by way of example and in highly schematic form. The illustrated bearing unit 2 is not necessarily a real situation, but rather FIG. 1 serves to explain different states. In the illustrated FIG. 1, the bearing unit 2 has two roller bearings 4 that are spaced from one another. The roller bearing 4 illustrated in the right-hand half of the image is in this case designed as a double-row, mounted and preloaded roller bearing. The roller bearing 4 illustrated in the left-hand half of the image is by contrast designed as a single-row roller bearing in the form of a floating bearing with positive bearing clearance (in contrast to the negative bearing clearance in the case of a preloaded bearing).
[0070]A respective roller bearing 4 in each case has at least an inner ring 6, an outer ring 8 and rolling bodies 10 arranged between them. In the case of the roller bearing 4 illustrated in the left-hand half of the image with the positive bearing clearanc...
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In the methods for monitoring a bearing clearance of a roller bearing (4), in particular the bearing clearance of a main bearing of a wind turbine, within the scope of a first measuring series using at least one distance sensor (18), a distance (a, a1, a2) between a rotating part (12) and a stationary part (14) is respectively sensed in at least two different recurring load states (L1, L2), and a difference (Δa) between the measured distances (a1, a2) is determined. At a later time the distance measurements are repeated in the same at least two recurring load states (L1, L2) within the scope of a second measuring series. A change in the bearing clearance is inferred on the basis of the changes in the distance difference (Δa) within the scope of condition monitoring.
Description
BACKGROUND OF THE INVENTIONField of the Invention[0001]The invention relates to a device and to a method for monitoring the state of the bearing clearance of a roller bearing, in particular the bearing clearance of a large bearing, specifically of a wind turbine, and in particular of a main bearing.Description of the Background Art[0002]State monitoring is in this case performed after the roller bearing is installed. Bearing clearance is understood to mean both a positive bearing clearance with bearing play and a negative bearing clearance (preloaded bearing) of roller bearing units. A roller bearing unit means in particular an individual bearing with attached parts (for example torque bearing) or a shaft system consisting of a shaft and a housing and any number of roller bearings.[0003]The bearings to be monitored are in general rotary bearings, that is to say bearings that rotate continuously about an axis of rotation during operation (and do not pivot just within a limited angula...
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IPC IPC(8): F16C19/38
CPCF16C19/38F16C2233/00F05B2240/50F16C19/386F16C19/522F16C41/00F16C2229/00F16C2300/14F16C2360/31F03D17/00F03D80/70G01M13/04Y02E10/72G01L5/00
InventorREICHHART, MARC
OwnerSCHAEFFLER MONITORING SERVICES GMBH