Test bench arrangement, test and evaluation device and method for calibrating bearing test bench

Abstract

The invention relates to a test and evaluation device (21) for calibrating bearing test benches (1, 20), comprising a plurality of bearing test benches (1, 20), each of which is designed as a friction test bench for testing a swivel bearing (2) having two bearing rings (6, 7). The test and evaluation device (21) further comprises data capture devices (17, 18) which are assigned to individual bearing test benches (1, 20) and which are connected to a common data processing unit (19) which is designed to compare specific properties of the bearing test benches (1, 20) with one another.

Description

Technical Field

[0001] The present invention relates to a testing and evaluation device intended for calibrating a bearing test stand, wherein the bearing test stand is a tribological test stand for testing rotating bearings, in particular rolling bearings, such as wheel bearings. The present invention also relates to a method for calibrating such a bearing test stand. Furthermore, the present invention relates to a test stand arrangement comprising a bearing test stand and a rolling bearing to be tested using the bearing test stand as a test specimen. Background Art

[0002] WO 2019 / 170186 A1 discloses a test bench and a method for testing bearing devices. In particular, the bearing device may be a rolling bearing for a wind turbine. WO 2019 / 170186 A1 assumes that natural conditions have a fundamental impact on the operation of the entire bearing. Based on this consideration, it proposes the definition of environmental scenarios that influence the service life of the bearing. This results in different load scenarios related to the bearing device, which are mapped to shortened test scenarios to minimize testing time. In the case of WO 2019 / 170186 A1, roller bearings are specifically tested.

[0003] For example, documents DE 10 2008 060 762 A1 and DE 10 2014 008 127 A1 describe devices for testing rolling bearings, which also include tilting moments in the test.

[0004] DE 10 2020 100 912 A1 is directed to testing rolling bearings using vibration analysis. A first bearing ring of the rolling bearing is driven, while a vibration signal is recorded on a second bearing ring.

[0005] Various test bench arrangements are shown in documents DE 10 2013 106 779 B4 and EP 2 264 421 B 1. In the case of the latter document, an electric motor is intended to drive and / or load the test specimen.

[0006] US Pat. No. 2,944,417 A shows a test bench designed for measuring long-term running procedures, in which a brake shoe acts on a rotating shaft. The device according to US Pat. No. 2,944,417 A is specifically designed for testing the friction properties of chemically treated metal surfaces. Summary of the Invention

[0007] The object of the present invention is to further develop a device and a method for testing bearings, in particular rolling bearings, compared to the cited prior art, wherein a particularly favorable relationship is sought between the equipment costs on the one hand and the accuracy and reproducibility of the test on the other hand, even when many measuring procedures are carried out according to a uniform test concept with multiple, similar or different devices.

[0008] According to the invention, this object is achieved by a testing and evaluation device that enables calibration of a bearing test stand having the features of claim 1. According to claim 4, the bearing test stand can in particular be a test stand with which tests are performed on unsealed, clearance-free double-row rolling bearings, in particular wheel bearings. This object is also achieved by a test stand arrangement configured according to claim 5, comprising a bearing test stand designed as a tribotest stand and a rolling bearing as a test specimen.

[0009] Furthermore, the object is achieved by a method for calibrating a bearing test stand designed as a tribological test stand, according to claim 6. The features and advantages of the invention explained below in conjunction with the calibration method also apply mutatis mutandis to the device, i.e. the test and evaluation device, the test stand arrangement and the individual test stands, and vice versa.

[0010] The testing and evaluation device according to the present application comprises a plurality of identical or different bearing test stands, each of which is designed as a tribological test stand for testing a rotary bearing having two bearing rings. Furthermore, the testing and evaluation device comprises a data acquisition device, which is assigned to the individual bearing test stands and is connected to a shared data processing unit, in a centralized or decentralized configuration, which is also assigned to the testing and evaluation device and is designed to compare specific characteristics of the bearing test stands with one another.

[0011] In particular, one of the bearing test rigs can be configured as a reference test rig, which can be operated with standardized test bearings. The test bearings can be, for example, rolling bearings. The same rolling bearing or the same type of rolling bearing can be tested on at least one other bearing test rig in order to test the properties of the bearing test rig in the context of calibration with the reference test rig.

[0012] The bearing test bench to be calibrated specifically enables the testing of rolling bearings, but is also intended for testing plain bearings. In both cases, tests under load, i.e. axial and / or radial test loads, can be performed. It is also possible to perform tests on the bearing without load.

[0013] In each case, the first bearing ring of the bearing can be held by a receptacle of the bearing test stand, while a hysteresis brake, also provided by the bearing test stand, acts on the second bearing ring. The torque introduced into the receptacle can be detected using a measuring device that is coupled to the aforementioned data acquisition device or integrated into such a device.

[0014] According to various possible designs, bearing test benches include a compressed air-operated lubrication device, by which the rotary bearings are lubricated during testing. The lubrication device is designed to supply lubricant to the rotary bearings, in particular rolling bearings, in a finely distributed manner using a compressed air flow in the form of air-oil lubrication. For possible forms of air-oil lubrication, reference is made to DE 10 2004 006 313 B4, DE 10 2014 209 235 A1, DE 000 SC 014461 MAZ, and WO 2012 / 010566 A1. In this case, the lubricant is supplied continuously or discontinuously to the rotary bearings to be tested using air-oil lubrication.

[0015] The lubrication device designed for oil mist lubrication made a significant contribution to ensuring that the bearing operated under substantially constant, defined conditions throughout the test, even over long periods of time, and thus complemented the hysteresis brake very well, which enabled fine adjustment of the braking torque acting on the bearing ring. For possible designs of hysteresis brakes, reference is made, for example, to US Pat. No. 6,257,380 B1, WO 96 / 01779 A1, and EP 0 960 467 B1.

[0016] There are essentially no restrictions regarding the size of the bearings to be tested when calibrating different bearing test stands or regarding the speeds and forces acting on the bearings. If the bearing is designed as a rolling bearing, it can be a single-row or multi-row bearing, in particular a clearance-free bearing.

[0017] In particular, the method according to the present application offers the possibility of performing dynamic calibration on rolling bearing tribology test rigs that can be operated in any location and not necessarily of identical design. If necessary, the test rig characteristics determined during the calibration of the bearing test rig can be used to adjust the parameters with which the test rig in question is operated. In principle, this adjustment can be performed automatically or by an operator.

[0018] For calibrating bearing test benches, which are also available from various manufacturers, clearance-free rolling bearings are particularly suitable, as their frictional properties hardly change. For example, double-row angular contact ball bearings in an O-shaped arrangement with a preload in the order of 10 μm to 20 μm are used as rolling bearings.

[0019] The present invention is based on the following considerations: Different basic designs of rolling bearing test rigs have specific advantages and disadvantages. For example, test rigs using three-ring bearings as support bearings are generally useful. In contrast, test rigs with hydrostatic support bearings are characterized by particularly low-friction operation, but dissipate heat into the test bearings. In principle, friction torque can also be measured without load and without support bearings. In all cases, varying heat dissipation from test rig to test rig can make test rig calibration difficult.

[0020] In the solution according to the application, comparison between different test benches is facilitated in particular by the fact that the lubricant flow supplied to the bearing, in particular the rolling bearing, by means of compressed air is directed out of the bearing again, so that easily reproducible conditions are achieved.

[0021] In general, the concept for testing rolling bearings implemented within the framework of the method according to the present application is characterized in that a torque, i.e. a resistance torque, is introduced into a first bearing ring of the rolling bearing by means of a hysteresis brake, while lubricant, in particular oil, is supplied to the rolling bearing by means of compressed air, and the torque supporting a second bearing ring of the rolling bearing is measured.

[0022] Because lubrication helps keep the temperature at least approximately constant, the inherent friction torque in rolling bearings remains stable even under load. To ensure unimpeded lubricant drainage from the rolling bearings, the bearings are advantageously operated in a test bench without seals. Instead of seals, a cover plate can be used that creates an air gap between the rotating and non-rotating bearing parts.

[0023] Heat dissipation from the rolling bearings is achieved, in particular, by compressed air, which is used to introduce lubricating oil into the rolling bearings. The amount of lubricating oil carried by the compressed air can be adjusted as needed, for example, to one drop of oil per minute. Generally speaking, the lubrication device is designed as a so-called drip lubricator. For example, this can be operated with compressed air at an overpressure of less than 5 bar.

[0024] The bearings used in the test bench, such as the inner ring of a double-row ball bearing, are supported by a main shaft that is subjected to a braking torque that can be adjusted with high precision using a hysteresis brake, in particular a precision hysteresis brake. Precise current supply units that enable the generation of a precisely defined magnetic field contribute particularly to the precise adjustability of the hysteresis brake. The hysteresis brake can be designed in conjunction with the rolling bearing to be tested so that at most a minimal heat flow is transferred from the hysteresis brake to the rolling bearing. In particular, guiding the material flow through the rolling bearing with the aid of a lubricating device can help minimize the heat transfer to the rolling bearing.

[0025] For example, a current-controlled precision laboratory power supply is suitable for energizing a hysteresis brake. This allows a constant, stable excitation current to be generated even when the temperature changes.

[0026] In addition to detecting the current used to operate the hysteresis brake, the direction of the current change can also be detected. With regard to the lubrication system, in particular, the air pressure and the amount of lubricant, i.e., the amount of oil delivered by the lubrication system, can be recorded during operation of the bearing test stand. Furthermore, the speed and temperature of the bearing can be detected.

[0027] The test bench arrangement according to the present application comprises a bearing test bench designed as a friction test bench and a rolling bearing as a test specimen. The bearing test bench has a hysteresis brake coupled to the bearing ring of the test specimen. Furthermore, the bearing test bench has a compressed air-operated lubrication device for lubricating the test specimen using air-oil lubrication. This lubrication device is designed not only to supply an air-oil mixture to the test specimen but also to permanently drain the lubricant flow supplied to the test specimen by compressed air. The test specimen used in the test bench arrangement, which enables calibration of the test bench, is a gapless, multi-row, in particular, double-row, unsealed rolling bearing.

[0028] Overall, the acquired data can be integrated into a measurement data acquisition strategy that is uniformly applied across multiple bearing test benches. This enables test bench calibration that goes far beyond static calibration.

[0029] For example, the bearing test bench is designed for carrying out measurements on wheel bearings for motor vehicles. Alternatively, a variant of the bearing test bench can be implemented in which larger bearings, in particular for stationary applications, are tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In the following, exemplary embodiments of the present invention are described in more detail with reference to the accompanying drawings, which show the following in a partially and roughly simplified manner:

[0031] Figure 1 A bearing test bench is shown in schematic cross-section,

[0032] Figure 2 A symbolic representation of a test and evaluation device intended for calibrating a test bench is shown, the test and evaluation device comprising a Figure 1 bearing test bench and another bearing test bench. DETAILED DESCRIPTION

[0033] A bearing test bench 1 is intended for testing a bearing 2, which in this case is a wheel bearing for a passenger car that has been specially modified for the test. The center axis of the bearing 2, i.e., the test specimen, designated MA, also represents the center axis of the bearing test bench 1. In the example, the center axis MA is aligned horizontally, but this is not mandatory. The bearing test bench 1 is also referred to as a reference test bench, while the bearing 2 is also referred to as a reference bearing. The testing and evaluation device, generally designated 21, serves to calibrate the characteristics of the reference test bench 1 by means of the characteristics of another bearing test bench 21, which in this case has a different design than the reference test bench 1.

[0034] Bearing 2 is designed as a double-row rolling bearing, whose rolling elements 3 and 4 are arranged in an O-shaped arrangement in bearing 2. The outer ring of bearing 2 is designated by 6, and the inner ring by 7. In known embodiments, a multi-part design of bearing rings 6 and 7 is possible. Bearing 2 is designed to absorb axial forces, radial forces, and tilting loads. The cage for guiding rolling elements 5, i.e., balls, is not shown. Contrary to the state of rolling bearings on the market, rolling bearing 2 is not sealed.

[0035] To lubricate the bearing 2 in the bearing test bench 1, a lubricating device 8 is provided. This lubricating device uses compressed air to introduce lubricant, i.e., oil, through the stationary outer ring 6 into the interior of the bearing, i.e., between the two rows of rolling elements 3, 4. In this way, air-oil lubrication, i.e., oil mist lubrication, of the bearing 2 is achieved.

[0036] The lubricating device 8 is designed as a drip lubricator operated by compressed air. The compressed air connection of the lubricating device 8 provided for this purpose is indicated by 9. The oil mist lubrication achieved by the lubricating device 8 consumes 1 drop of oil per minute and operates at a pressure of 5 bar applied to the compressed air connection 9. The oil mist can leave the bearing at the end face of the bearing 2, as shown in FIG. Figure 1 In the upper area of ​​the rolling bearing is indicated. Instead of a non-existent seal, a cover plate is present (in Figure 1 (not shown in the figure), the cover plate leaves an air gap of 0.2 mm wide. Compared to a seal, the cover plate has no braking effect. Due to the absence of a seal, no overpressure or underpressure can build up in the bearing 2 during test bench operation.

[0037] To brake the rotating bearing ring 7, i.e., the inner ring, in a defined manner, the bearing test stand 1 has a hysteresis brake 10. The hysteresis brake 10 is designed as an electronically controlled resistance device. The rotor of the hysteresis brake, designated 11, is connected to the inner ring 7 in a rotationally fixed manner. The associated stator of the hysteresis brake 10, designated 12, is mechanically coupled to the outer ring 6 via a retainer 13. The retainer 13 absorbs torques introduced into the outer ring 6 of the rolling bearing 2 during operation.

[0038] The measuring device 15 is provided for measuring the supported torque, wherein the mechanical connection between the outer ring 6 and the measuring device 15 is indicated by 14. Figure 1 Unlike the simplified representation in , the connecting part 14 can be located between the outer ring 6 and the holder 13, also called the receiving part, wherein the measuring device 15 converts the force acting on the connecting part 14 - or the deformation of the connecting part 14 caused by this force - into an electrical signal, which is further processed in digital form.

[0039] like Figure 1 As sketched in FIG, the measuring device 15 is supported on a surrounding structure 16, which is not necessarily part of the bearing test bench 1. The drag torque generated by the hysteresis brake 10 at a defined level acts in the same direction as the friction torque of the rolling bearing 2. The lubrication device 8 is adjusted so that the bearing 2 operates at a constant temperature throughout the test procedure.

[0040] Regarding the overall structure of the testing and evaluation device 21, refer to Figure 2 Therefore, each of the bearing test stands 1, 21 to be calibrated is assigned a data capture device 17, 18. The measuring device 15 ( Figure 2 ) are part of the respective data capture devices 17 , 18 .

[0041] The data capture devices 17, 18 are connected to a data processing unit 19, wherein Figure 2 The division shown in 1 into two data capture devices 17 , 18 and a single data processing unit 19 is to be understood functionally and does not imply any statement about the actual positioning of the data processing components and their separation or combination.

[0042] In any case, the data processing unit 19 performs measurements with the different bearing test benches 1 , 21 . This calibration serves in particular to detect deviations of the characteristics of the bearing test bench 21 from the characteristics of the reference test bench 1 .

[0043] like Figure 2 As further illustrated in FIG, a data line 22 is provided, by means of which the bearing test stands 1, 21 are connected to the data processing unit 19. In particular, this makes it possible to use the results of measurements taken during operation of the various bearing test stands 1, 21 to readjust the operating parameters for future operation of the bearing test stands 1, 21. This applies in particular to the bearing test stand 21. In a manner not shown, the reference test stand 1 can be used to perform calibrations with any number of additional bearing test stands 20.

[0044] Reference Signs List

[0045] 1Bearing test bench, reference test bench

[0046] 2 Bearings, rotary bearings, rolling bearings, test specimens

[0047] 3 Rolling elements in rows

[0048] 4 Rolling elements in rows

[0049] 5 Balls and rolling elements

[0050] 6 Outer Ring

[0051] 7 Inner Ring

[0052] 8 Lubrication device

[0053] 9 Compressed air connection

[0054] 10 Hysteresis brake

[0055] 11 rotor

[0056] 12 stator

[0057] 13 Reception Department

[0058] 14 Mechanical connection part

[0059] 15 Measuring device

[0060] 16 Surrounding structures

[0061] 17 Data Capture Device

[0062] 18 Data Capture Device

[0063] 19 Data Processing Unit

[0064] 20 Bearing test bench

[0065] 21 Test and evaluation equipment

[0066] 22 data cable

[0067] MA central axis.

Claims

1. A test and evaluation device (21) for calibrating bearing test stands (1, 20), comprising a plurality of bearing test stands (1, 20), each of the bearing test stands being designed as a tribological test stand for testing a rotary bearing (2) having two bearing rings (6, 7), and comprising a data acquisition device (17, 18) which is assigned to the individual bearing test stands (1, 20) and is connected to a common data processing unit (19) which is designed to compare specific characteristics of the bearing test stands (1, 20) with one another.

2. The testing and evaluation device (21) according to claim 1, characterized in that At least one of the bearing test stands (1, 20) has a receptacle (13) for holding a first bearing ring (6), a hysteresis brake (10) for braking a second bearing ring (7), and a measuring device (15) for measuring a torque introduced into the receptacle (13).

3. The testing and evaluation device (21) according to claim 1 or 2, characterized in that At least one of the bearing test stands (1, 20) has a compressed air-operated lubrication device (8) for lubricating the rotary bearing (2) by air-oil lubrication.

4. Use of the testing and evaluation device (21) according to claim 1 for carrying out tests on a clearance-free, unsealed double-row rolling bearing (2) by means of the bearing test bench (1, 20).

5. A test bench arrangement comprising a bearing test bench (1, 20) designed as a friction test bench and a rolling bearing as a test specimen (2), wherein: -The bearing test bench (1, 20) has o a hysteresis brake (10) coupled to the bearing rings (6, 7) of the test specimen (2), and a compressed air-operated lubricating device (8) intended for lubricating the test specimen (2) by air-oil lubrication, the compressed air-operated lubricating device being designed to permanently discharge the flow of lubricant supplied to the test specimen (2) by compressed air, and - The test specimen (2) is designed as a clearance-free, multi-row, unsealed bearing.

6. A method for calibrating a bearing test stand (1, 20) designed as a friction test stand, wherein: Similar or identical rotary bearings (2), each comprising two bearing rings (6, 7), are tested with the aid of the bearing test bench (1, 20) by introducing a torque into one of the two bearing rings (7) with the aid of a hysteresis brake, while simultaneously measuring the torque supporting the other bearing ring (6), and wherein specific characteristics of the bearing test benches (1, 20) detected during the testing of the rotary bearings (2) are compared with one another.

7. The method according to claim 6, characterized in that In at least one of the bearing test stands (1, 20), lubricant is supplied to the rotary bearing (2) by means of compressed air in the sense of oil-air lubrication.

8. The method according to claim 7, characterized in that A lubricant flow supplied by compressed air is permanently discharged from the rolling bearing (2).

9. The method according to any one of claims 6 to 8, characterized in that During the test, the speed and temperature of the rolling bearing (2) were also recorded.

10. The method according to claim 9, characterized in that The temperature of the rolling bearing (2) is kept constant by the supplied lubricant.

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