DE102019218884B4 - Slewing bearings and methods for measuring wear - Google Patents

Abstract

Large rolling bearing with a first bearing ring (1) with a first rolling body raceway (3), a second bearing ring (2) with a second rolling body raceway (4), a gap (5) formed between the first (1) and the second bearing ring (2) and with spherical rolling elements (6) which are arranged in the gap (5) and which roll on the first (3) and the second rolling element raceway (4), the first bearing ring (1) having a bore (7) in which a a distance sensor (8) designed as an inductive eddy current sensor is arranged, characterized in that the bore (7) receiving the distance sensor (8) is aligned so that its center line runs in the radial direction of the large roller bearing and one through the centers of the spherical rolling bodies (6) extending circular line intersects, whereby the distance sensor (8) can generate eddy currents in a rolling body (6) arranged opposite the distance sensor (8), so that a minimum distance between the distance sensor (8) and the rolling body (6) can be measured in the radial direction of the large rolling bearing , and wherein the rolling elements (6) are biased in the radial direction against the first bearing ring (1) at least in the peripheral region of the first bearing ring (1), in which the distance sensor (8) is arranged, in such a way that even in the event of deformations occurring during operation the bearing rings (1, 2), the rolling body (6) directly opposite the distance sensor (8) always remains in contact with the first rolling body raceway (3) and is constantly in contact with it.

Description

The invention relates to a large rolling bearing according to claim 1.

It is known from the prior art to use inductive distance sensors to measure the wear of rolling bearings and in particular of the rolling element raceways of rolling bearings. One goal is to identify the need for maintenance on a rolling bearing at an early stage and to be able to plan and carry out necessary maintenance measures in a timely manner. The wear of the rolling bearing usually consists of material removal or damage such as cracks or splinters, in particular on the surfaces that absorb loads (e.g. forces, moments, etc.) and thus in particular on the rolling element raceways on which the rolling elements roll.

The German patent application DE 10 2016 116 113 A1 describes a large slewing bearing with a first and a second bearing ring and a method for monitoring wear of the bearing. For the purpose of monitoring wear, the bearing has two sensors, which can be designed as eddy current sensors. The sensors are arranged in one of the two bearing rings of the bearing. One of the sensors interacts with a reference edge and the other sensor interacts with a reference surface, the reference edge and reference surface being formed on the other bearing ring. One of the sensors is used to measure the radial distance of a sensor surface of this sensor to the reference surface, so it functions as a distance sensor. This distance sensor measures according to the method DE 10 2016 116 113 A1 This ultimately reduces wear by measuring the radial change in distance between the two bearing rings DE 10 2016 116 113 A1 another sensor is mandatory to measure an axial displacement of the bearing rings relative to one another. This further sensor works together with a measuring edge formed on the bearing ring opposite the sensor.

In the case of rolling bearings with large diameters, the sometimes very large mechanical loads that occur during operation of the bearing and to which the bearing rings are exposed can cause significant elastic deformations of the bearing rings. These elastic deformations of the bearing rings are also referred to as ovalization of the bearing rings. These deformations or ovalizations distort the measurement results of the distance sensor DE 10 2016 116 113 A1 , because the measured distance changes are partly based on the deformations/ovalizations of the bearing rings and not just on wear of the rolling element raceways. Therefore, it is not possible to draw immediate conclusions about the wear condition of the bearing from these measured values. In order to be able to determine the actual wear of the rolling element raceways from the measured values obtained in this way, those portions of the measurement signals that are based on deformations/ovalizations of the bearing rings must be filtered out using a complex downstream analysis and evaluation process. This increases the procedural effort and poses the risk of incorrect determinations of the wear condition of the bearing.

The German patent application DE 10 2012 024 269 A1 also describes a large rolling bearing with a distance sensor that is used to determine the wear condition of the bearing. Here too, the change in distance between the two bearing rings is measured. For that from the DE 10 2012 024 269 A1 Known bearings and measuring methods therefore have the same problems and disadvantages as those described above in the patent application DE 10 2016 116 113 A1 have been shown.

In the US patent application US 2016 / 0 123 839 A1 A bearing device with an inner ring, an outer ring and a roller element which is arranged between the inner race and the outer race is described. The bearing device has a first sensor for detecting the displacement of the inner race, the outer race or the roller element. The first sensor serves to provide a first signal for the sensed displacement in order to determine a load acting on the bearing device. A determination of the wear condition of the bearing device is made in the US 2016 / 0 123 839 A1 not addressed.

The present invention is based on the object of specifying a large rolling bearing and a method for measuring wear, in which measured values are obtained which are independent of any elastic deformations/ovalizations of the bearing rings and from which the state of wear of the bearing can be determined directly and without complex filtering out of wear-independent measured value components can.

This task is solved by a large slewing bearing according to claim 1 and by a method according to claim 9.

Advantageous developments of the large slewing bearing according to the invention result from the subclaims relating to the independent claim, the following description and the drawings. Advantageous developments of the method according to the invention result from the subclaim relating back to the independent procedural claim, the following description and the drawings.

• 1) die den Abstandssensor aufnehmende Bohrung ist so ausgerichtet, dass ihre Mittellinie in radialer Richtung des Wälzlagers verläuft und eine durch die Mittelpunkte der kugelförmigen Wälzkörper verlaufende Kreislinie schneidet,
• 2) durch den Abstandssensor sind Wirbelströme in den Wälzkörpern erzeugbar, so dass ein minimaler Abstand zwischen Abstandssensor und Wälzkörper in radialer Richtung des Großwälzlagers messbar ist, und
• 3) die Wälzkörper sind zumindest in dem Umfangsbereich des ersten Lagerrings, in dem der Abstandssensor angeordnet ist, in radialer Richtung gegen den ersten Lagerring (1) derart vorgespannt, dass auch bei im Betrieb auftretenden Verformungen der Lagerringe (1, 2) der dem Abstandssensor (8) unmittelbar gegenüberliegende Wälzkörper (6) stets in Kontakt bleibt mit der ersten Wälzkörperlaufbahn (3) und ständig an dieser anliegt.

The invention is based on the knowledge that the disruptive influence of the deformations/ovalizations of the bearing rings on the measured values of the distance sensor can be avoided if the following design conditions are met:

• 1) the bore accommodating the distance sensor is aligned so that its center line runs in the radial direction of the rolling bearing and intersects a circular line running through the centers of the spherical rolling elements,
• 2) the distance sensor can generate eddy currents in the rolling elements, so that a minimum distance between the distance sensor and the rolling element can be measured in the radial direction of the large roller bearing, and
• 3) the rolling elements are prestressed in the radial direction against the first bearing ring (1), at least in the peripheral region of the first bearing ring in which the distance sensor is arranged, in such a way that even if the bearing rings (1, 2) are deformed during operation, the distance sensor (8) directly opposite rolling elements (6) always remain in contact with the first rolling element raceway (3) and are constantly in contact with it.

By implementing the first and second conditions mentioned above, it is achieved that the sensor measures the distance in the radial direction to the ball over the entire surface and thereby detects the minimum distance between the sensor and the spherical rolling body. By implementing the third aforementioned condition, it is achieved that the spherical rolling bodies always make contact with the bearing ring in which the distance sensor is arranged. This ensures that even if deformations/ovalizations of the bearing rings occur (for example as a result of large forces occurring during operation of the bearing), the rolling elements do not lose contact with the raceway of the bearing ring carrying the distance sensor.

As a result, by implementing all three of the aforementioned conditions, a rolling bearing is provided in which the wear of the bearing in the area of the raceways can be measured precisely while excluding distorting influences from elastic deformations of the bearing rings.

The circular line that runs through the centers of the spherical rolling elements and connects these centers is also referred to by experts as the “circle of rotation”.

The hole for receiving the distance sensor can basically be positioned at different points on the bearing ring within the range of the pressure angle of a rolling element. It is possible to arrange this hole in such a way that the rolling element rolls over the area in which the hole is located. However, it is also possible to arrange the bore in a position in the bearing ring in which the rolling element does not roll over the area of the bore.

According to one embodiment of the invention, a storage and evaluation unit is provided, wherein the distance sensor and the storage and evaluation unit are coupled to one another in such a way that the measurement signals from the distance sensor can be transmitted to the storage and evaluation unit. The coupling between the distance sensor and the storage and evaluation unit can be implemented in different ways. If the bearing ring carrying the distance sensor is arranged in a rotationally fixed manner, then it is easily possible to connect the distance sensor to the storage and evaluation unit via one or more cables and to transmit the measured values via the cable or cables. But even if the bearing ring carrying the distance sensor is the rotatably arranged bearing ring that rotates during operation of the bearing, the distance sensor can be coupled to the storage and evaluation unit via cable. In this case, the storage and evaluation unit should be attached to a component or a connecting structure of the bearing that rotates with the rotating bearing ring, i.e. that does not exert any rotational movement relative to the rotating bearing ring. An example of this would be a rotatably mounted inner ring of a bearing for an excavator, with which a structure of the excavator is rotatably mounted relative to the substructure of the excavator. The inner ring is connected to the structure in a rotationally fixed manner. The storage and evaluation unit is connected to the structure. The distance sensor can then be coupled to the storage and evaluation unit via cable connections. The cable connection can be used not only to transmit the measured values of the distance sensor to the storage and evaluation unit, but also to supply the distance sensor with the current or electrical voltage required for its operation.

However, in an alternative embodiment, it is also possible to couple the distance sensor to the storage and evaluation unit without contact (for example via a radio connection). In this case, the measurement signals from the distance sensor are transmitted to the storage and evaluation unit via radio. This embodiment has the advantage that the distance sensor supporting bearing ring does not have to be arranged in a rotationally fixed manner, but can also be arranged rotatably.

The storage and evaluation unit can have a WLAN module for transmitting the data to external devices such as a smartphone or a tablet.

According to one embodiment of the invention, the first bearing ring is arranged in a rotationally fixed manner and the second bearing ring is arranged rotatably relative to the first bearing ring. In this case, the distance sensor is arranged in the bearing ring, which is arranged in a rotationally fixed manner.

The distance sensor can therefore be coupled to the storage and evaluation unit in a simple manner via cable connections. In this case, the distance sensor can also be powered via the cable connection.

According to another embodiment of the invention, the first bearing ring is arranged rotatably and the second bearing ring is arranged in a rotationally fixed manner. In this case, the distance sensor is coupled to the storage and evaluation unit without contact and the measured values of the distance sensor are transmitted to the storage and evaluation unit without contact. For example, the contactless coupling and transmission of the measured values can take place via a radio connection. The energy source required for the operation of the radio connection and the transmission of the measurement signals can be accommodated in the distance sensor. A battery can be used as an energy source.

According to one embodiment of the invention, the large rolling bearing is designed as a four-point bearing, which has a non-load-bearing area between the rolling body raceways, the distance sensor being arranged in this non-load-bearing area. The non-load-bearing area usually serves as a lubrication groove. Arranging the distance sensor in this non-supporting area has the advantage that the sensor can be arranged without the receiving hole for the sensor disturbing the geometry of the rolling body contact.

According to one embodiment of the invention, the bearing is designed as a deep groove ball bearing, with the distance sensor being arranged in a peripheral section of the bearing that is lightly loaded in the operating state. Arranging the distance sensor in a peripheral section that is lightly loaded during operation of the bearing has the advantage that the hole for receiving the sensor does not permanently disrupt the rolling contact between the rolling element and the raceway.

According to the invention, the distance sensor and its arrangement in the large roller bearing are intended to measure the radial approach between the sensor-carrying bearing ring and a rolling body positioned directly opposite the sensor during operation of the bearing. Preferably, the arrangement takes place in that ring that is under “point load”, i.e. that bearing ring that is repeatedly subjected to maximum load at approximately the same circumferential position during operation of the bearing, and where wear can therefore be expected to begin. “Point load” refers, for example, to the rotatably arranged (“rotating”) bearing ring connected to the boom of an excavator or crane, which is always subjected to maximum stress under and in relation to the boom. “Point load” also includes, for example, the non-rotatable (“standing”) bearing ring (outer or inner ring) of a gravity-loaded drum bearing with a horizontal axis of rotation (e.g. cable drum, washing drum, coating drum and the like), which is always at the highest point (at 12 o’clock with a “standing” inner ring) or at the lowest point (at 6 o’clock with a “standing” outer ring).

In the case of a drum bearing loaded by gravity and designed as a deep-groove ball bearing (for example a bearing of a cable drum, washing drum, coating drum or similar) with an inner ring that is arranged in a rotationally fixed manner and carries the distance sensor, the distance sensor can advantageously be located in the circumferential area between 9:00 a.m. and 10:00 a.m or in the area between 2 and 3 o'clock. If the outer ring is arranged in a rotationally fixed manner and carries the distance sensor, then the distance sensor can advantageously be arranged in the circumferential area between 3 and 4 o'clock or 8 and 9 o'clock.

According to one embodiment of the invention, the distance sensor is arranged at a distance from the rolling elements which is dimensioned such that the distance sensor does not touch the rolling elements even at maximum wear. In this way, damage to the sensor due to contact with the rolling elements is reliably avoided. It has been shown that unwanted contact between the distance sensor and the rolling elements can be avoided if the distance of the distance sensor to the rolling element surface of a rolling element directly opposite the distance sensor is at least 7% of the rolling element diameter in a bearing without wear.

With regard to the method according to the invention, the above-mentioned technical problem is solved by a method for measuring wear on the rolling element raceways of a ball slewing ring with a first bearing ring a first rolling body raceway, a second bearing ring with a second rolling body raceway, a gap formed between the first and the second bearing ring and with spherical rolling bodies which are arranged in the gap and which roll on the first and the second raceway, the first bearing ring having a bore has, in which a distance sensor designed as an inductive eddy current sensor is arranged, wherein the first bearing ring is arranged in a rotationally fixed manner and the second bearing ring is arranged rotatably relative to the first bearing ring. According to the invention, the distance sensor generates eddy currents in a rolling body arranged opposite the distance sensor, the rolling body being biased in the radial direction against the first bearing ring by a pretensioning force at least in the peripheral region of the first bearing ring in which the distance sensor is arranged in such a way that even during operation occurring deformations of the bearing rings, the rolling body directly opposite the distance sensor always remains in contact with the first rolling body raceway and is constantly in contact with it, the distance sensor detecting a minimum distance between a rolling body and the distance sensor and the measurement signals belonging to this minimum distance to a storage and evaluation unit be passed on.

According to one embodiment of the method according to the invention, the results of a distance measurement are compared in the storage and evaluation unit with a stored threshold value or reference value, with a maintenance requirement signal being generated and output if the result of a distance measurement corresponds to the threshold value or reference value or is below the threshold value or reference value . In this way, the continuous measurement of the distance values helps ensure that maintenance work can be carried out on the slewing bearing before the bearing fails. In this way, the availability of the machine or device containing the large slewing bearing is increased and downtimes can be prevented or at least minimized.

With appropriate calibration on a new bearing without wear or on a bearing with only slight wear, the measuring arrangement according to the invention can also be used for rough load measurements in the applications described above. The sensor locally measures the proximity between the ball and the raceway. The contact between the ball and the raceway can be viewed as a spring element. If the spring rate (spring stiffness) of the contact is known (e.g. from: analytical calculation, FEM calculation or calibration test (few loads with known weights)), the existing load can be calculated from the product of the approximation and spring rate. The latter works particularly well if the main load direction is always the same and the sensor is arranged exactly in this direction (e.g. radial sensor arrangement in the main load zone of a bearing loaded by gravity with a horizontal axis of rotation (e.g. drum bearing).

The “rough” restriction refers to the usually limited resolution of the sensors and the fact that the spring rate is usually only known for the undamaged new bearing.

It is to be expected that with slightly preloaded bearings, the sensor signals on an intact, unworn bearing will fluctuate less due to the lower play (“zero play”). From this initial situation, the progression of wear (towards significantly more play) can be detected more clearly.

If, for example, the distance sensor is arranged in the main load zone of a bearing loaded by gravity, e.g. in a "drum bearing", then the radial preload of the bearing at the measuring location is already given by gravity, i.e. gravity ensures that the rolling elements are against the Raceway of the bearing ring carrying the distance sensor are prestressed.

In other installation situations, a slight preload can be introduced by using oversized balls when assembling the bearing.

The invention is explained in more detail below with reference to a drawing. The only 1 shows schematically the use of the invention using the example of a deep groove ball bearing, more precisely a so-called “light” ball slewing ring.

This type of slewing bearing is referred to as a “light” ball slewing ring because they are low in weight in relation to their diameter and the bearing rings have a comparatively high elastic deformation capacity with large diameters at the same time. Therefore, the deformations/ovalizations that occur during operation under load are clearly pronounced in these large slewing bearings. Distance measuring systems that measure the distance between a distance sensor connected to one of the bearing rings and an object that is part of the other bearing ring therefore provide both bearings of this type with measured values that are significantly distorted by the deformations/ovalizations of the bearing rings.

This in 1 The large rolling bearing shown has a first bearing ring 1 and a second bearing ring 2. In the illustrated embodiment, the first bearing ring 1 is arranged in a rotationally fixed manner and the second bearing ring 2 is arranged rotatably relative to the first bearing ring 1. There is a gap 5 between the two bearing rings. Spherical rolling bodies 6 are arranged in the gap 5 and distributed over the circumference. The rolling elements 6 roll on rolling element raceways 3, 4. The first rolling element raceway 3 is formed on the first bearing ring 1 and the second rolling body raceway 4 is formed on the second bearing ring 2.

The first bearing ring 1 has a fastening flange extending in the radial direction R, in which fastening holes 9 are arranged distributed over the circumference. An annular section 10 of the bearing ring 1 extends perpendicular to the radial direction R in the axial direction. In this annular section 10, a bore 7 is provided, in which a distance sensor 8 designed as an eddy current sensor is accommodated. In the example shown, an existing grease hole 7 in the bearing was used for the sensor 8. This means that no further holes need to be made in the ring (loss of rigidity). A separate hole is only necessary if no grease hole has been made in the ring at a suitable location.

The bore 7 is aligned so that its center line intersects a circular line connecting the centers of the spherical rolling bodies 6. As a result, the sensor measures the distance in the radial direction to the ball over the entire surface and thereby detects the minimum distance between the sensor and the spherical rolling element.

In the 1 a situation is shown in which the rolling body 6 is arranged directly opposite the distance sensor. The distance sensor 8 generates eddy currents in the rolling body 6 directly opposite it, so that a minimum distance between the distance sensor 8 and the rolling body 6 is measured in the radial direction of the large rolling bearing.

The rolling elements 6 are prestressed in the radial direction R against the first bearing ring 1 (more precisely against the first rolling element raceway 3 of the first bearing ring 1) by a pretensioning force (not shown) in the peripheral region of the first bearing ring 1, in which the distance sensor 8 is arranged. The preload is carried out in such a way that even when deformations of the bearing rings 1, 2 occur during operation, the rolling body 6 directly opposite the distance sensor 8 always remains in contact with the first rolling body raceway 3 and is constantly in contact with it. The deformations/ovalizations of the bearing rings therefore do not falsify the measurement result of the distance sensor 8. The actual wear of the rolling element raceways 3, 4 is measured in this way without falsifying the measured values.

In the exemplary embodiment shown, the measured values measured by the distance sensor 8 are transmitted to a storage and evaluation unit, not shown, via a cable (not shown for reasons of clarity) and stored there. In the storage and evaluation unit, the distance measurement values are compared with a stored reference or threshold value. This reference or threshold value describes a critical distance value, below which a maintenance measure must be carried out on the slewing bearing. If the storage and evaluation unit determines that the measured distance values are equal to or less than the reference or threshold value, a maintenance requirement signal is generated and output. In this way, timely maintenance can be carried out in such a way that failure or failure of the bearing and the machine or device equipped with the bearing is prevented or minimized.

Reference symbol list

1

Bearing ring

2

Bearing ring

3

rolling element raceway

4

rolling element raceway

5

gap

6

rolling elements

7

drilling

8th

Distance sensor

9

mounting hole

10

Section

R

Radial direction

Claims (10)

Large rolling bearing with a first bearing ring (1) with a first rolling body raceway (3), a second bearing ring (2) with a second rolling body raceway (4), a gap (5) formed between the first (1) and the second bearing ring (2) and with spherical rolling elements (6) which are arranged in the gap (5) and which roll on the first (3) and the second rolling element raceway (4), the first bearing ring (1) having a bore (7) in which a Distance sensor (8) designed as an inductive eddy current sensor is arranged, characterized in that the bore (7) receiving the distance sensor (8) is aligned so that its center line runs in the radial direction of the large rolling bearing and intersects a circular line running through the center points of the spherical rolling bodies (6), with the distance sensor (8) Eddy currents can be generated in a rolling body (6) arranged opposite the distance sensor (8), so that a minimum distance between the distance sensor (8) and the rolling body (6) can be measured in the radial direction of the large rolling bearing, and the rolling bodies (6) at least in that Circumferential area of the first bearing ring (1), in which the distance sensor (8) is arranged, is prestressed in the radial direction against the first bearing ring (1) in such a way that even if the bearing rings (1, 2) are deformed during operation, the distance sensor ( 8) immediately opposite rolling elements (6) always remain in contact with the first rolling element raceway (3) and are constantly in contact with it. Slewing bearings Claim 1 , characterized in that a storage and evaluation unit is provided, and that the distance sensor (8) and the storage and evaluation unit are coupled to one another in such a way that the measurement signals from the distance sensor (8) can be transmitted to the storage and evaluation unit. Slewing bearings Claim 1 or 2 , characterized in that the first bearing ring (1) is arranged in a rotationally fixed manner and the second bearing ring (2) is arranged rotatably relative to the first bearing ring (1). Slewing bearings Claim 1 or 2 , characterized in that the first bearing ring (1) is arranged rotatably and the second bearing ring (2) is arranged in a rotationally fixed manner. Large rolling bearing according to one of the preceding claims, characterized in that the bearing is designed as a four-point bearing which has a non-load-bearing area between the rolling body raceways (3, 4), the distance sensor (8) being arranged in this non-supporting area. Slewing bearing according to one of the Claims 1 until 4 , characterized in that the bearing is designed as a deep groove ball bearing, the distance sensor (8) being arranged in a peripheral section of the bearing that is lightly loaded in the operating state. Large rolling bearing according to one of the preceding claims, characterized in that the distance sensor (8) is arranged at a distance from the rolling elements (6) which is dimensioned such that the distance sensor (8) does not touch the rolling elements (6) even at maximum wear . Slewing bearings Claim 7 , characterized in that the distance of the distance sensor (8) to a surface of a rolling body (6) directly opposite the distance sensor (8) is at least 7% of the rolling body diameter in a bearing without wear. Method for measuring wear on the rolling body raceways (3, 4) of a ball slewing ring with a first bearing ring (1) with a first rolling body raceway (3), a second bearing ring (2) with a second rolling body raceway (4), one between the first (1) and the gap (5) formed in the second bearing ring (2) and with spherical rolling elements (6) which are arranged in the gap (5) and which roll on the first (3) and the second raceway (4), the first bearing ring (1 ) has a bore (7) in which a distance sensor (8) designed as an inductive eddy current sensor is arranged, the first bearing ring (1) being arranged in a rotationally fixed manner and the second bearing ring (2) being arranged rotatably relative to the first bearing ring (1). , characterized in that the distance sensor (8) generates eddy currents in a rolling body (6) arranged directly opposite the distance sensor (8), the rolling body (6) being influenced by a preload force at least in the peripheral region of the first bearing ring (1), in which the Distance sensor (8) is arranged, is biased in the radial direction against the first bearing ring (1) in such a way that the rolling body (6) directly opposite the distance sensor (8) is always in contact, even when deformations of the bearing rings (1, 2) occur during operation remains with the first rolling element raceway (3) and is constantly in contact with it, the distance sensor (8) detecting a minimum distance between the rolling element (6) and the distance sensor (8) and passing on the measurement signals associated with this minimum distance to a storage and evaluation unit become. Procedure according to Claim 9 , characterized in that in the storage and evaluation unit the results of a distance measurement are compared with a stored threshold value or reference value, with a maintenance requirement signal being generated and output if the result of a distance measurement corresponds to the threshold value or reference value or is below the threshold value or reference value.

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