WO2011124501A1

WO2011124501A1 - Measuring system for rolling bearings

Info

Publication number: WO2011124501A1
Application number: PCT/EP2011/054789
Authority: WO
Inventors: Jens Heim; Darius Dlugai; Marc-André SCHÄFER
Original assignee: Schaeffler Technologies Gmbh & Co. Kg
Priority date: 2010-04-06
Filing date: 2011-03-29
Publication date: 2011-10-13
Also published as: DE102010013934A1

Abstract

The invention relates to a measuring system for a rolling bearing, in particular a wheel bearing, comprising two sensors (11, 30; 10, 32) enabling detection of the effects of a source of interference when determining a measurement value for the interior of the rolling bearing and for generating an interference-free measurement signal allowing conclusions about the operating state of the rolling bearing, or the service life thereof. Said aim is achieved in that both sensors for a rolling bearing unit of the type indicated are provided for monitoring effects of different intensities of a source of interference on the measurement variable at both measurement locations, also known as temperature gradients, and for identifying or excluding the source of interference. The invention can be used in wheel bearings and transmission bearings of all types, in particular for commercial vehicles and trailers. The invention can also be conceivably used in wind power plants or other industrial plants having high outage costs and high monitoring requirements.

Description

Name of the invention

Measuring system for rolling bearings

The invention relates to a measuring system for monitoring a rolling bearing, comprising a first measuring element for monitoring a measured variable at a first measuring point, wherein the first measuring point is arranged in the vicinity of the Wälzrau- mes of the rolling bearing or in the rolling space of the rolling bearing and by means of the first measuring element predominantly effects of a rolling bearing operation can be monitored on the measured variable and an evaluation unit, which is provided for evaluating a first signal of the first measuring element and a second signal of a second measuring element by comparing the two signals. State of the art

Background of the invention

Measuring systems for rolling bearings are widely used for monitoring the rolling bearings by regularly measuring measured variables such as structure-borne noise, temperature, humidity or strain and load measurements on the roller bearing and then evaluating them by means of an evaluation unit. Such measuring systems can be used for example in rolling bearings in wind turbines, engines or wheel bearings. In the vicinity of the bearing inner space, also called the rolling space, a measuring element is mounted, which detects one of the aforementioned measured variables and can be forwarded to an evaluation unit. It is of particular interest to recognize the approaching end of life of the rolling bearing. For example, in aircraft construction, but also in motor vehicle construction, it is indispensable to predict a wear-related failure of the rolling bearing early enough for safety reasons to prevent potentially dangerous failure of the rolling bearing during operation of the rolling bearing.

Dangerous situations can arise in particular with so-called wheel runners in commercial vehicles, since the rolling elements in a wheel bearing have been worn out due to greatly increased friction in such a way that the two opposing bearing rings could move away from each other. As a result, the wheel of the commercial vehicle runs off together with the rotatable part of the wheel bearing and poses an extreme danger to road users in traffic. The situation is similar for roller bearings of an aircraft engine or even in an industrial plant.

From DE 200 0 6 944 U1 a device for reporting a puncture to a vehicle wheel is known, which has four driving noise receiving sensors in the vicinity of the wheel bearing, whose signals are arranged by a transmitter within the interior of the tire. The central evaluation device has a receiver which receives the sensor signals and forwards the evaluation. By comparing the different sensor signals, the central evaluation device can detect whether a detected noise is a problem which is located at one of the four wheel bearings or whether the sound was caused only by a special road surface covering all four sensors. This can be used to detect if a problem has occurred at a wheel bearing. Unfortunately, such systems for a so-called end-of-life detection can not be used because the bearings are in the same life stage, and thus have the same abrasion, or the same wear and a comparison between the sensor signals thus allows no conclusion on the wear of the bearings.

From US 5 959 365 A a warning device is known, which also allows to monitor wheel bearing units of a vehicle separately and to compare the measured values with each other, wherein the measuring system detects temperature or structure-borne noise.

Furthermore, the measuring systems mentioned can not recognize whether their respective measured value of a sensor can be assigned to the rolling bearing, or is still influenced by other units. For example, it is not possible to filter out interference frequencies that may be generated by the drive (eg motor, drive shaft or the like), since these vibrations usually penetrate into all wheel bearing units, whether driven or not. Such a source of interference could occur with the measuring systems according to The prior art can not be recognized. The same applies to wheel bearing units with brake assembly, which also lead to an increase in temperature of the wheel bearing and thus let the temperature sensor arranged there detect a measured values that is not representative of the wheel bearing unit, i. no conclusions on the current condition of the wheel bearing unit permits. For this reason, conventional measuring systems can only be operated with large measuring errors due to these sources of interference.

task

Summary of the invention

The object of the invention is therefore to propose a measuring system which can reliably detect sources of interference and, if appropriate, permits statements about the end of life of a rolling bearing.

The object is achieved by a wheel bearing unit of the type mentioned in that the second measuring element for monitoring the measured variable is provided at a second measuring point in the vicinity of the rolling bearing, and both measuring elements monitor effects of a source of interference on the measured variable at the two measuring points in order to identify or exclude the source of interference.

According to the invention, the measuring system for monitoring a rolling bearing, in particular wheel bearing, two measuring elements. The first measuring element is located near the interior of the rolling bearing, called further Wälzraum. The rolling space includes the load bearing rolling elements and is limited by one or more outer and one or more inner rings. Furthermore, it can also be limited by one or two sealing arrangements, which seal the rolling bearing mainly in the axial direction. A measuring point is understood to be a location at which a measuring element can be attached without influencing a function of the rolling bearing. In this case, fastening elements can be provided locally on an inner ring, outer ring or on a sealing arrangement, which hold the measuring element at the measuring point. A measuring point thus essentially refers to the location of the arrangement of the measuring element, but may also be characterized by fastening means.

The first measuring point is provided for the first measuring element and is chosen such that the measured variable of the interior of the rolling bearing is optimally measurable. The measured variable is, for example, a temperature, a structure-borne noise, a moisture, a lubricant quantity, a lubricant state, an elongation, a load, or a distance between two bearing parts, which may be rotatable relative to one another. The measuring elements are designed according to the measured variable to be measured, for example, a temperature measuring element has a temperature-dependent resistance element, which is arranged in a circuit and whose voltage is measured. An elongation or a load can be detected by a force measuring element, as for example play through so-called strain gauges (DMS). For the other measured data, there are corresponding measuring elements or sensors that can be used for the respective measured variable. With the first measuring element, the measured variable is monitored at a first measuring point in the vicinity of the rolling space, wherein the first measuring point is arranged in the vicinity of the rolling space. Thus, predominantly effects of a rolling bearing operation on the measured variable at the first measuring point can be monitored.

The evaluation unit is provided to receive the first signal of the first measuring element and the second signal of the second measuring element and to compare the two signals with each other. This can be done for example by means of one or more mathematical operations, wherein an intermediate or final result can lead to an electronic output or an acoustic warning signal or a comparable signal compared to reference data, if the evaluation of the evaluation has revealed that a serious problem, such eg the approaching end of life of the rolling bearing is present. By evaluating the evaluation thus sources of interference can be excluded or clearly identified, which measures can be initiated before the failure of the bearing.

According to the invention, a second measuring element for monitoring the measured variable is provided at a second measuring point in the vicinity of the rolling space of the rolling bearing in order to monitor different intensity effects of an interference source on the measured variable at the two measuring points. For example, under a source of interference, a braking device may be considered, which constitutes a heat source in the vicinity of a wheel bearing due to the friction heating. Thus, the wheel bearing is warmed up due to the usually very good conductive metallic components of the bearing. This thermal energy penetrates into the rolling space up to the interior of the rolling bearing and is also detected by the first measuring element there. Since the second measuring element is arranged in the vicinity of the heat source, and therefore mainly detects the effects of the sources of interference, a statement can be made from the knowledge of the thermal conductivity between the two measuring points, to what extent the measured value of the first measuring element is due to a heating of the wheel bearing, or to a heating by the interference sources. It is quite possible that both measuring elements detect the sources of interference, as well as the heat source of self-heating of the bearing, but a weighting of the measured values due to the different distance to the source of interference is required. This makes it possible to measure the so-called temperature gradient between the two measuring points and to decide how much heat energy is actually due to the operation of the wheel bearing and also in which direction the heat is conducted. The invention can accordingly be used not only on wheel bearings, but on any other type of rolling bearing in which a source of interference occurs. The decisive factor is that the measuring points of the two measuring elements occupy different distances from the interference source in order to produce a meaningful difference in measured values.

A measured variable may be, for example, twill sound. In this case, elements of a drive, such as a drive shaft, a universal joint, a constant velocity joint or the engine can be a source of interference. Corresponding sources of interference are likewise known for the aforementioned measured quantities. If the measured quantity is a moisture, then the second measuring element could be located in an annular space of the sealing arrangement, which is less intensively sealed than the rolling space and thus represents an antechamber. It can be clearly recognized how much moisture has already penetrated through the seal assembly into the interior of the bearing. If the measured moisture measurement values are very different, it can be assumed that the seal arrangement is largely operable. However, if you have adjusted to a certain degree, then you can conclude that the seal assembly is no longer tight enough and must be replaced. Alternatively, a prediction can be made by the evaluation unit as to how long the rolling bearing will still be operable. In an advantageous embodiment, the first and second measuring point are arranged between a first and a second bearing part, wherein the bearing parts each form at least one rolling body track. It is also possible to arrange both measuring points within the rolling space or the second measuring point at least within the sealing arrangement. Thus, both measuring points between a rotating bearing parts and a fixed bearing part, which may be an outer ring, an inner ring or a hub. This results in a roller bearing which has measuring points on the respective opposing raceways of the rolling bodies and which detect the same measured value with respect to the bearing operation. This is because the upper and lower rolling body raceways are exposed to substantially similar operating conditions, so that the same measuring conditions prevail at the outer and inner bearing part. In the case of the measured variable temperature, the measured temperature measured values of the two measuring elements deviate from one another when the effects of an interference source acting more strongly on one of the two measuring elements from radially outside or radially inward than the other. It is advantageous that a rolling bearing unit can be prefabricated with two measuring elements and is able to detect whether an elevated temperature originates from the interior of the Wälzla- gers or from outside of it. The same applies to other parameters. Irrespective of the measured variable, the first bearing part can be rotatable relative to the second bearing part and the first measuring point can be arranged on the first bearing part and the second measuring point on the second bearing part. In an advantageous embodiment, the second measuring point is arranged in the vicinity of the source of interference. Here, one is not limited to provide the measuring point on the rolling bearing, but can even arrange the measuring point in the vicinity of the sources of interference and connect to the evaluation by cable or wirelessly. For example, it is conceivable to apply a second temperature measuring element directly to a mounting of a brake assembly, or to place a sound-measuring element in the vicinity of the motor or to fasten other measuring elements for other measured variables in the vicinity of the respective interference source. Advantageously, the source of interference is a brake assembly, a hub, in particular wheel hub, or a component of the drive. In addition, the invention can be used in various types of rolling bearings, which are arranged in the vicinity of sources of interference.

Advantageously, the measured variable is a temperature, a structure-borne sound, a moisture, a lubricant quantity, a lubricant state, a torsion, an elongation or a distance between rolling bearing parts. In addition, it is possible to arrange a plurality of measuring elements of different types at a measuring point, so that both temperature values, sound values etc. can be measured simultaneously and the evaluation unit is also forwarded, so that several statements about the rolling bearing can be made in the form of an analysis. In an advantageous embodiment, the first and / or the second measuring element is integrated into a sealing arrangement, in particular a cassette seal, of the rolling bearing. This results in easy installability together with the cassette seal, which is pressed in the axial direction on a rotatable and a static bearing part. The installation of the two measuring elements can thus take place on the comparatively easy-to-shape sealing arrangement instead of on a hard-to-manufacture inner ring, outer rings or the like.

In an advantageous embodiment, the first measuring element or the second measuring element on the rotatable part of the seal assembly and the respective other measuring element on the static part of the seal assembly is fixed. For the measuring element, which is fixed to the rotatable bearing part, often worth a wireless connection to evaluation, which is completely wireless or at least partially wireless. The measuring element on the fixed bearing part can be connected to the evaluation unit with a cable. In exceptional cases, a wireless connection is also conceivable here if, for example, the evaluation unit and the said sensor are mounted on different parts, which are minimally in contact with each other during operation can move. This happens, for example, with an inner ring placed on an axle journal, which can move relative to an evaluation unit on the axle journal. Consequently, it may be advantageous to provide the measuring system to transmit the first and / or second signal wirelessly to the evaluation unit. In addition, this results in advantages in the installation, as cables are usually a source of error in the installation of rolling bearings. The measuring system according to the invention can be used together with roller bearings, in particular wheel bearings, wherein rolling elements are provided in opposite raceways relative to each other rotatable bearing parts for load-bearing rolling. However, it is quite possible that the second measuring element is mounted outside the rolling bearing in order to detect a measured variable in the vicinity of the interference source.

Basically, the use of the measuring system according to the invention in rolling bearings with rolling elements is possible, which are provided in opposite raceways relative to each other rotatable bearing parts for load-bearing rolling.

Further advantageous embodiments and preferred developments of the inven tion are the figure description and / or the dependent claims to take ent.

In the following the invention will be described and explained with reference to exemplary embodiments illustrated in the figures.

1 shows a first, integrated in a wheel bearing measuring system

Fig. 2 shows a second, integrated in a wheel bearing with a speed measuring system measuring system, and Fig. 3 shows a third, retrofittable measuring system for a rolling bearing.

embodiment

Description of the drawings

Fig. 1 shows a first, integrated in a wheel bearing measuring system.

In the wheel bearing is a wheel bearing for a commercial vehicle with an outer ring 1, an inner ring 3 and rolling rolling elements under load 2. It is a double-row wheel bearing, with only the right half is shown with a row of rolling elements 2 in section. The rolling elements 2 are tapered rollers which rotate about an axis of rotation of the wheel bearing (not shown) and their own axis of symmetry 4.

Between the outer ring 1 and the inner ring 3, a seal assembly is pressed, which has a carrier 6 which is fixed to the rotatable outer ring 1 and has a further ring 5 which is arranged on the fixed inner ring 3.

The first sensor is formed by the first measuring element 1 1, which rests against the inner ring 3 and is connected to an evaluation unit 13. Intermediate see the measuring element 1 1 and the evaluation unit 13, the ring 5 is arranged, wherein the connections between the measuring element 1 1 and evaluation unit 13 is accomplished by axial holes. A similar connection exists between the evaluation unit 13 and the receiver 16, which is provided for the wireless connection of the evaluation unit 13 with the second sensor formed from the second measuring element 10 and the transmission element 12. The second sensor also has direct contact with the outer ring 1 via the second measuring element 10, with which, for example, a measured value, such as, for example, a temperature or structure-borne noise, can be measured. In addition, the wireless connection between the transmission element 12 and the receiver 16 for detecting the distance of the outer ring 1 to the inner ring 3 can be measured. Such a distance is relevant for the so-called end-of-life detection, since in so-called Radabläufern the outer ring 1 moves away from the inner ring 3, wherein the rolling elements 2 are plastically deformed due to the resulting frictional heat, that the bearing rings no longer positively are connected to each other via the rolling elements 2.

In the wireless connection is in the transmission element 12, for example, an antenna that is optionally designed as a transponder or connected to a transponder and wirelessly can be powered by a radio frequency from the receiver 16 with energy, this energy at the same time for the detection of the measuring element 10 is usable. The signal is then also transmitted to the receiver 16 via the same frequency. The measuring elements 10, 1 may be provided for measuring a temperature, with both measuring elements providing the same signal when the temperature within the rolling bearing is determined solely by the operation thereof (no source of interference present). This is due to the fact that the outer ring 1 and the inner ring 3 are equally heated by the rolling elements 2 rolling off, and thus the inner surface of the outer ring 1 or the outer surface of the inner ring 3 generally have the same temperature. This changes when, for example, heat from a brake disk (interference source) attached to the outer ring 1 enters the rolling bearing, which has been passed through the outer ring 1. This heat flow can be measured in particular by the measuring element 10, but also to a lesser extent by the measuring element 11. This temperature gradient between the two bearing ring surfaces is detected by the measuring system and determined by the evaluation unit 13 by comparing the two signals. Possibly In the output unit 13 reference data are stored in a storage medium, so that it can be seen how hot the brake disk is as a function of the measured temperature gradient. The reference data have been determined in knowledge of the conductivity and the distance between the brake disc and the measuring element 10 before commissioning of the illustrated wheel bearing in the form of calibration measurements.

It should be noted that the elastic part 7 forms a radial sealing lip, which bears sealingly against a cylindrical part of the ring 5 and has a significantly lower conductivity than the metal or metals used to produce the rolling elements 2 and the bearing rings 1, 3 has been / are used.

The evaluation unit 13 has a cable 14, at the end of a plug 15 is attached, which allows the evaluation unit 14 to connect to the electronics of a truck. About this cable 14, a warning signal can be passed, which can report too hot a brake assembly, but also a total too hot running bearings. A warning signal can be created by the evaluation unit 13 itself, or by an element of the vehicle electronics, such as an on-board computer.

The embodiment shown is not limited to an arrangement in a wheel bearing, but is used in a plurality of roller bearings, which are to be sealed between inner (3) and outer ring 1 with a sealing arrangement, in particular with a cassette seal. Advantageously, this cassette seal, which has the entire measuring system can be pressed together with this in the rolling bearing.

The measuring elements 10, 1 can also be embodied as sound sensors, with which a source of interference, which lies radially outward or radially inward, with respect to the axis of rotation of the bearing, can be recognized as such and their different effects on the measuring elements 10, 1 1 are detectable. If, for example, the temperature at the measuring point of the measuring element 10 begins to rise, it is to be expected that the temperature during the measuring point of the measuring element 11 will also increase as a function of this. How fast this happens can be determined on the basis of a physical model under signal progression at the measuring points. This model can be determined from the rolling bearing design by taking into account the conductivity in each bearing component. This can always reliably a statement about the temperature inside the bearing, ie in the vicinity of the rolling contact, are ensured.

Ideally, the measuring element 10 and the measuring element 1 1 are intended to detect both temperature and sound. Thus, different types of sources of interference can be detected at the same time, or their effects can be analyzed.

If the measuring elements are intended to detect sound, then it can be easily distinguished whether the truck wheel bearing is defective, or whether the structure-borne noise comes from tire-road contact, or comes from driven axles from the gearbox or from defective axle joints.

Fig. 2 shows a second, integrated in a speed measuring system measuring system.

The speed measuring arrangement consists of an encoder ring 20 fastened to the rotatable outer ring 25, which has a signaling area 24. The signaling area 24 is arranged axially with respect to a measuring element 33, which can detect alternating north and south poles of the signaling area 24. The measuring element 33 is arranged in a sensor 34, which is also provided for the detection of a temperature gradient according to the invention.

For this purpose, the sensor 34 has an evaluation unit 31, which with a measuring element 30 via a receiving element 35 and also via a cable with a second measuring element 32 is connected. The measuring elements 30, 32 are provided for measuring the temperature at their respective measuring points. The measuring point of the measuring element 30 is located in a ring 22 of a seal assembly, which still has a sealing ring 21 with an elastic member 23. Thus, the measuring element 30 is in an annular sealing space between a radial sealing lip and an axial sealing lip. Advantageously, the measuring element 30 is thereby protected, but is still close enough to the receiving element 35, wherein during the rolling bearing temperature data between the measuring element 30 and the receiving element 35 are transmitted wirelessly.

Thus, the sensor 34 is used for the wireless recording of rolling bearing data, wherein the temperature data are already evaluated in the evaluation unit 31.

The measuring point 32 is located in the vicinity of a caliper and absorbs the temperature of the "braking arrangement" source of interference. The temperature value obtained in this way is compared with the temperature value of the measuring point 30, so that it can be determined whether the heat is mainly from the rolling bearing or from the brake arrangement is generated.

Advantageously, the measuring system according to the invention can be combined with a known speed arrangement, wherein no additional installation steps for the car manufacturer are necessary. The seal assembly is supplied, for example, as a cassette seal and already contains the measuring element 30. The same applies to the sensor 34, which can be installed in the same way.

FIG. 3 shows a retrofittable measuring system for a roller bearing 36, which is completely integrated in a sensor 39. The measuring element 37 is closer to the rolling bearing 36 and also closer to the rolling space than the measuring element 38. With adequate coupling of the sensor 39 to the rolling bearing 36, the effect on the measuring element 38 will always be smaller than on the measuring element 37th Other sources of sound, such as the engine or tire-road contact, act evenly on the gauges 37, 38, so that damage to the roller bearing 36 is distinguishable from other interfering sound source sources. The same applies to other sources of interference, such as a temperature.

It is advantageous that the integrated measuring system in the sensor 39 can be easily retrofitted by retrofitting. For this purpose, an evaluation unit can be provided in the sensor. Alternatively, the sensor 39 can be connected to an evaluation unit by cable 40.

In summary, the invention relates to a measuring system for a rolling bearing, in particular wheel bearing, which has two sensors, which make it possible to detect the influence of a source of interference in the determination of a measured value for the rolling bearing interior and to generate a trouble-free measurement signal, which statements about the operating condition of the bearing or its life allows. This is achieved in that in a rolling bearing unit of the type mentioned both sensors are provided to monitor different intense effects of a source of interference on the measured variable at the two measuring points, also called temperature gradient, or to identify or exclude the source of interference. The invention can be used in wheel bearings and gearbox bearings in vehicles of all kinds, especially in commercial vehicles and trailers. Also conceivable is the use of wind turbines or other industrial plants with high downtime costs and large monitoring needs. LIST OF REFERENCE NUMBERS

Outer ring 36 Rolling bearings

Rolling element 37 measuring element

Inner ring 38 measuring element

Rotation axis 39 sensor

Ring 40 cables

sealing ring

Radial sealing lip

measuring element

transmission element

evaluation

electric wire

plug

receiver

signaler

sealing ring

ring

Elastic part

Signaling area

outer ring

measuring element

evaluation

measuring element

sensor

receiving element

Claims

claims

Measuring system for monitoring a rolling bearing, comprising:

- A first measuring element (1 1, 30) for monitoring a measured variable at a first measuring point, wherein the first measuring point in the vicinity of the rolling space of the rolling bearing or in the rolling space of the rolling bearing is arranged and by means of the first measuring element (1 1, 30) predominantly effects a rolling bearing operation can be monitored for the measured variable,

- An evaluation unit (31), which is provided for evaluating a first signal of the first measuring element (1 1, 30) and a second signal of a second measuring element (10, 32) by comparing the two signals, characterized in that the second measuring element (10, 32) for monitoring the measured variable at a second measuring point in the vicinity of the rolling space of the rolling bearing o- is provided in the rolling space of the rolling bearing, and both measuring elements (10, 1 1, 31, 32) effects of a source of interference on the measured variable Monitor the two measuring points to identify or exclude the source of interference.

Measuring system according to claim 1, wherein the first and second measuring point between a first (3) and a second bearing part (1) are arranged, wherein the bearing parts (13) each form at least one rolling body track.

Measuring system according to claim 1 or 2, wherein the first bearing part (3) relative to the second bearing part (1) is rotatable and wherein the first measuring point on the first bearing part (3) and the second measuring point on the second bearing part (1) is arranged.

Measuring system according to one of the preceding claims, wherein the second measuring point is arranged in the vicinity of the interference source.

Measuring system according to claim 4, wherein the source of interference is a brake assembly, a hub or a component of the drive.

Measuring system according to claim 1, wherein the measured variable is a temperature, a structure-borne sound, a humidity, a lubricant amount, a lubricant state, a torsion, an elongation or a distance between rolling bearing parts.

7. Measuring system according to claim 1, wherein the measuring system is provided to transmit the first and / or second signal wirelessly to the evaluation unit (31).

8. Measuring system according to claim 1, wherein the measuring system is designed as a sensor (39) and has a first (37) and second measuring element (38).

Sealing arrangement, in particular a cassette seal, with a measuring system according to claim 1, wherein the first (1 1, 30) and / or the second measuring element (10, 32) is / are integrated in the sealing arrangement of the rolling bearing. O. The sealing arrangement according to claim 9, wherein the first measuring element (11, 30) or the second measuring element (10, 32) on the rotatable part of the sealing arrangement and the respective other measuring element (10.1 1, 30, 32) on the static part the seal assembly is fixed. Rolling, in particular wheel bearing, with a measuring system according to one of the preceding claims 6 to 7 or a seal arrangement according to one of claims 9 or 10, wherein rolling elements are provided in opposite raceways relative to each other rotatable bearing parts for load-bearing rolling.