DE102010013934A1 - Measuring system for rolling bearings - Google Patents

Abstract

In summary, the invention relates to a measuring system for a roller bearing, in particular a wheel bearing, which has two sensors that make it possible to detect the influence of a source of interference when determining a measured value for the inside of the roller bearing and to generate an interference-free measurement signal that provides information about the operating state of the roller bearing or whose service life allows. This is achieved in that in a rolling bearing unit of the type mentioned, both sensors are provided to monitor the effects of a source of interference on the measured variable at the two measuring points, also known as temperature gradients, or to identify or exclude the source of interference. The invention can be used for wheel bearings and gearbox bearings in vehicles of all types, in particular in utility vehicles and trailers. It is also conceivable to use it in wind turbines or other industrial systems with high downtime costs and great monitoring needs.

Description

Field of the invention

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 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 predominantly effects of a rolling bearing operation can be monitored to 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

Rolling bearing measuring systems are widely used for rolling bearing monitoring by measuring such variables as the number of rolling bearings. As structure-borne noise, temperature, humidity or strain and load measurements are measured regularly on roller bearings and then evaluated by 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 interior, also called the rolling space, a measuring element is mounted, which detects one of the aforementioned measured variables and can be passed on 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-induced failure of the rolling bearing early enough so that, for safety reasons, a possibly extremely dangerous failure of the rolling bearing during operation of the same can be avoided.

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 represents an extreme danger to road users in traffic. The situation is similar for rolling bearings of an aircraft engine, or in an industrial plant.

Out 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 pneumatic 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, since 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 no conclusion on the wear of the bearings allows.

Out US 5,959,365 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, 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), as these vibrations usually penetrate into all wheel bearing units, whether driven or not. Such a source of interference could not be detected with the measuring systems according to the prior art. 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, which is not representative of the wheel bearing unit, d. H. 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 reliably Determine sources of interference and, if necessary, allows statements about the end of life of a rolling bearing.

The object is achieved by a wheel bearing unit of the type mentioned above in that the second measuring element is provided for monitoring the measured variable at a second measuring point in the vicinity of the rolling bearing, and monitor both measuring elements effects of a source of interference on the measured variable at the two measuring points to the Identify or exclude 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. Elongation or stress can be detected by a force sensing element, such as 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 as z. As the approaching end of life of the 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 a source of interference 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 heat energy penetrates into the interior of the rolling bearing to the rolling space and is also detected by the local first measuring element. Since the second measuring element is arranged in the vicinity of the heat source, and therefore predominantly detects the effects of the interference sources, 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 to a heating of the wheel bearing, or due to heating by the sources of interference. 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 is correspondingly applicable not only to wheel bearings, but to any other type of rolling bearing, in which a source of interference occurs. Decisive is that the measuring points of the two measuring elements different distances from the Take the source of interference to produce a meaningful difference in the measured value.

A measured variable may be, for example, twill sound. In this case, elements of a drive, such as. As a drive shaft, a universal joint, a constant velocity universal joint or the engine constitute 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 creates a roller bearing, which has measuring points on the respective opposite raceways of the rolling elements 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 measuring conditions are the same at the outer and inner bearing parts. 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 rolling bearing or from outside 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 engine or to fasten other measuring elements for other measured variables in the vicinity of the respective source of interference.

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 be done on the comparatively easy to be formed seal assembly 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 with a cable to the evaluation unit. In exceptional cases Here, too, a wireless connection conceivable, for example, if the evaluation unit and the said sensor are mounted on different parts, which can move slightly against each other during operation. 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 invention can be taken from the description of the figures and / or the dependent claims.

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

Show it:

1 a first measuring system integrated in a wheel bearing,

2 a second, integrated in a wheel bearing with a speed measuring assembly measuring system, and

3 a third, retrofittable measuring system for a rolling bearing.

embodiment

Description of the drawings

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

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 with a row of rolling elements 2 is shown in sectional view. At the rolling elements 2 they are tapered rollers, which are located about an axis of rotation of the wheel bearing (not shown) and their own axis of symmetry 4 rotate.

Between the outer ring 1 and the inner ring 3 is a seal assembly pressed in, which is a carrier 6 having, on the rotatable outer ring 1 is fixed and another ring 5 which is on the stationary inner ring 3 is arranged.

The first sensor is the first measuring element 11 formed, which on the inner ring 3 is present and with an evaluation unit 13 connected is. Between the measuring element 11 and the evaluation unit 13 is the ring 5 arranged, with the connections between measuring element 11 and evaluation unit 13 is accomplished by axial holes. A similar connection exists between the evaluation unit 13 and the receiver 16 , to the wireless connection of the evaluation unit 13 with the from the second measuring element 10 and the transmission element 12 formed second sensor is provided.

The second sensor also has the second measuring element 10 direct contact with the outer ring 1 with which, for example, a measured value, such as a temperature or structure-borne noise, can be measured. In addition, the wireless connection is between the transmission element 12 and the receiver 16 for detecting the distance of the outer ring 1 to the inner ring 3 measurable. Such a distance is relevant for the so-called end-of-life detection, since in so-called Radabläufern the outer ring 1 from the inner ring 3 moved away, the rolling elements 2 due to the resulting frictional heat are plastically deformed so that the bearing rings no longer form fit over the rolling elements 2 connected to each other.

The wireless connection is the transmission element 12 for example, an antenna, which is optionally designed as a transponder or connected to a transponder and wirelessly via a radio frequency from the receiver 16 can be energized, this energy at the same time for the detection by the measuring element 10 is usable. The signal then becomes the measuring element via the same frequency 10 to the recipient 16 transfer.

The measuring elements 10 . 11 may be provided for measuring a temperature, wherein both measuring elements provide the same signal when the temperature within the rolling bearing is determined solely by the operation of the same (no source of interference present). This is because the outer ring 1 and the inner ring 3 equally by the rolling rolling elements 2 are heated and thus the inner surface of the outer ring 1 or the outer surface of the inner ring 3 usually the same temperature. This changes when, for example, one of the outer ring 1 attached brake disc (source of interference) heat enters the rolling bearing, passing through the outer ring 1 was conducted. This heat flow is in particular due to the measuring element 10 , but also to a lesser extent by the measuring element 11 measurable. This temperature gradient between the two bearing ring surfaces is detected by the measuring system and by the evaluation unit 13 determined by comparing the two signals. Optionally, in the output unit 13 Reference data stored in a storage medium, so that it can be seen how hot the brake disc is in dependence of the measured temperature gradient. The reference data are in knowledge of the conductivity and the distance between the brake disc and the measuring element 10 was determined prior to commissioning of the illustrated wheel bearing in the form of calibration measurements.

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

The evaluation unit 13 has a cable 14 on, at the end of a plug 15 is attached, which allows the evaluation unit 14 to connect with the electronics of a truck. About this cable 14 can be passed a warning signal, which can report too hot a brake assembly, but also a total overheated bearings. A warning signal can be sent from the evaluation unit 13 be created by yourself, 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 rolling bearings, the between inner ( 3 ) and outer ring 1 to be sealed 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 . 11 can also be designed as sound sensors, whereby a source of interference, which is 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 . 11 are detectable.

For example, the temperature starts at the measuring point of the measuring element 10 To rise, it is to be expected that also the temperature during the measuring point of the measuring element 11 depending on it will increase. How fast this happens can be determined on the basis of a physical model under signal course 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 11 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.

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

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

This is indicated by the sensor 34 an evaluation unit 31 on that with a measuring element 30 via a receiving element 35 and also via a cable with a second measuring element 32 connected is. 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 in a ring 22 a seal assembly that still has a sealing ring 21 with an elastic part 23 having. This is the measuring element 30 in an annular sealing space between a radial sealing lip and an axial sealing lip. Advantageously, the measuring element 30 protected by it, but still close enough to the receiving element 35 , wherein during the rolling bearing operation temperature data between the measuring element 30 and the receiving element 35 be transmitted wirelessly.

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

The measuring point 32 is located near a caliper and absorbs the temperature of the source of interference "brake assembly". The thus obtained temperature value, with the temperature value of the measuring point 30 compared, so that it can be seen whether the heat is mainly generated by the rolling bearing or by the brake assembly.

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.

3 shows a retrofittable measuring system for a rolling bearing 36 which completely in a sensor 39 is integrated. The measuring element 37 is closer to the rolling bearing 36 and also closer to its rolling space than the measuring element 38 , With adequate coupling the sensor 39 to the rolling bearing 36 becomes the effect on the measuring element 38 always be smaller than on the measuring element 37 ,

Other sound sources, such. As the engine or the tire-road contact act on the measuring elements 37 . 38 evenly, causing damage to the rolling bearing 36 is distinguishable from other interfering sound source sources. The same applies to other sources of interference, such. B. a temperature.

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

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 old vehicles, especially 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

1

outer ring

2

rolling elements

3

inner ring

4

axis of rotation

5

ring

6

sealing ring

7

Radial sealing lip

10

measuring element

11

measuring element

12

transmission element

13

evaluation

14

electric wire

15

plug

16

receiver

20

signaler

21

sealing ring

22

ring

23

Elastic part

24

Signaling area

25

outer ring

30

measuring element

31

evaluation

32

measuring element

33

measuring element

34

sensor

35

receiving element

36

roller bearing

37

measuring element

38

measuring element

39

sensor

40

electric wire

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 20006944 U1 [0005]
• US 5959365 A [0007]

Claims (11)

Measuring system for monitoring a rolling bearing, comprising: - a first measuring element ( 11 . 30 ) for monitoring a measured variable at a first measuring point, wherein the first measuring point is arranged in the vicinity of the rolling space of the rolling bearing or in the rolling space of the rolling bearing and by means of the first measuring element ( 11 . 30 ) predominantly effects of a rolling bearing operation can be monitored on the measured variable, - an evaluation unit ( 31 ) for evaluating a first signal of the first measuring element ( 11 . 30 ) and a second signal of a second measuring element ( 10 . 32 ) is provided by a comparison of the two signals, characterized in that the second measuring element ( 10 . 32 ) is provided for monitoring the measured variable at a second measuring point in the vicinity of the rolling space of the rolling bearing or in the rolling space of the rolling bearing, and both measuring elements ( 10 . 11 . 31 . 32 ) Monitor the 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. Measuring system according to claim 1, wherein the first and second measuring points are arranged 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 ) opposite the second bearing part ( 1 ) 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. 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 (11). 31 ) transferred to. Measuring system according to Claim 1, the measuring system being used as a sensor ( 39 ) and a first ( 37 ) and second measuring element ( 38 ) having. A sealing arrangement, in particular a cartridge seal, with a measuring system according to claim 1, wherein the first ( 11 . 30 ) and / or the second measuring element ( 10 . 32 ) is integrated in the seal assembly of the rolling bearing is / are. 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 . 11 . 30 . 32 ) is fixed to the static part of the seal assembly. 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.

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