WO2008104163A1

WO2008104163A1 - Method and device for testing rolling bearing cages

Info

Publication number: WO2008104163A1
Application number: PCT/DE2008/000340
Authority: WO
Inventors: Richard Mützel
Original assignee: Schaeffler Kg
Priority date: 2007-02-28
Filing date: 2008-02-26
Publication date: 2008-09-04
Also published as: DE102007009706A1

Abstract

The invention relates to a method and a device for testing rolling bearing cages, which can be used to determine the mechanical characteristics of rolling bearing cages with the minimum of resources, in order to draw reliable conclusions and make predictions about the reliability and load-bearing capacity of these bearing components. According to the invention, two cage bars (18, 19) are clamped between holders (1, 2) that have contact surfaces (31, 56) adapted to the contours of the cage bars (18, 19). A test force that acts on the cage bars (18, 19) is introduced into said bars via the holders (1, 2) and the force is directed and measured in such a way that a varying tensile load (62) is exerted on each cage bar (18, 19).

Description

Name of the invention

Method and device for testing roller bearing cages

description

Field of the invention

The invention is in the field of test methods with which the mechanical properties of rolling bearing cages, in particular Cylindrical roller bearing cages, can be determined and documented, and relates to a method for testing roller bearing cages with cage webs.

Manufacturers of rolling bearings are faced with increasingly high demands of the customers with regard to the expected life of the rolling bearings. An influencing factor on the service life of rolling bearings is the expected number of cycles of the rolling bearing cage, which can be expected at a given load before failure or breakage of the rolling bearing cage. This aspect in the determination of the life of rolling bearings has received little attention so far. So far, the assembled, complete bearings are usually tested or were determined from the operation of the bearing life-determining data. Damage or destruction of the roller bearing cage that can be observed during bearing damage can result from a wide variety of influencing variables, whereby the respective damage-relevant load component can not be identified or separated.

With regard to the design of rolling bearings or the assurance of certain lifetimes, this has led to a lower, a significant safety margin-containing rating of the rolling bearing load capacity was made without specific proof of load.

Also in the area of roller bearings, increasing cost pressure is to be observed, which also influences the design of rolling bearing cages. Common are solid brass cages, which are very expensive to manufacture and thus represent a significant cost factor. In addition, mostly two-piece, so-called comb cages are known, each having a bottom and a lid. Floor and lid are connected by riveting.

Against this background, the present invention has for its object to provide a test method and a test apparatus for performing the method, with which the mechanical properties of rolling bearing cages can be determined with little effort to draw reliable conclusions and forecasts to be able to reliability and Resilience of these bearing components.

This object is achieved by a method with the features of claim 1 and with a test device with the features of claim 8. Accordingly, in the method for testing roller bearing cages, two cage webs are clamped between receptacles which have contact areas adapted to the contour of the cage webs. About the shots acting on the cage web test force is initiated, which is directed and dimensioned so that a varying tensile load and / or an alternating tensile and compressive load is exerted on the respective cage web.

The term cage web is to be understood in the context of the present invention. It includes all suitable for connecting the two circumferential edges (hereinafter also called top or bottom) of the rolling bearing cage, between them a so-called cage pocket for receiving a rolling element forming elements. These elements may be formed, for example, strip-like with an approximately rectangular cross section, wherein the axially parallel to the bearing axis extending longitudinal sides of the rectangular cross-section for adaptation to the running surfaces of the rolling elements (for example, cylindrical roller shape) are concave.

A particular aspect of the invention consists in that the receptacles each have at least one contact surface or a contact region, which is designed so that it applies the test force surface on the respective web.

The test force can preferably be directed and dimensioned by oscillating excitation of the recordings so that each cage web is alternately exposed to a compressive or tensile load. This has the advantage that with each test cycle a load zero crossing occurs, so that even in a load orientation recognizable damage (such as loosening cage parts connecting rivets) can be easily detected. An advantageous embodiment of the method according to the invention provides that the test object used is a sector separated from a roller bearing cage with at least two cage webs. This advantageously contains only two cage webs and thus extends over a complete cage pocket and in each case to half of the side edge of the adjacent cage pocket on both sides of the segment. This can be generated in an advantageous manner from a rolling bearing cage by cutting or cutting after every two cage bars a Prüflingsanzahl that corresponds to half (even) number of cage pockets.

The test force can be generated particularly easily by a uniaxial so-called hydropulser, which is set into vertical oscillations by appropriate hydraulic pulsating action which are transmitted to at least one vertically movable receptacle. In this case, the dynamic load can advantageously be produced in a particularly reproducible manner by simple means if a test force is used which causes sinusoidal loadings of the cage webs between pressure and train.

More preferably, the tensile load of the cage webs is set such that it is higher in magnitude than the pressure load of the webs. In this way, it is ensured that a test cycle always passes through a zero crossing, so that any loosened rivet connections can be reliably detected, especially in the case of two-part roller bearing cages, during the pressurization.

In practice, it has proved to be sufficient and preferred in terms of validity, that the test load or the resulting Zugbzw. Pressure loads are selected or set so that a load cycle number of approximately 10 ⁶ cycles results before the test specimen fatigues or breaks. The test device according to the invention has two receptacles for the tensile and / or pressure-transmitting receptacle each of a cage web of a roller bearing cage, wherein the receptacles have contact areas which are adapted or adaptable to the shape of the cage web. It also has a drive means acting on the recordings for dynamic, alternating tensile and compressive loading of the cage webs.

Particularly preferably, the recordings are formed by bars between which a cage bar can be clamped.

For equipping the test device with test objects, it is particularly preferred if the receptacles each have a position-adjustable element for clamping the cage web. The position adjustment of the element can be done for example by screw and thread on the principle of spindle and spindle nut.

More preferably, at least one receptacle is connected via an elastic element to the drive device, which permits an elastic movement of the receptacle. An elastic connection of the receptacle can take place via a respective leaf spring, which is screwed to a test cylinder or the force transducer of the drive device. By means of the leaf spring, the required tensile or compressive forces are reliably transmitted for the test, while still allowing tilting of the receptacles about an axis extending substantially perpendicular to the cage webs and extending in the radial direction of the rolling bearing cage. As a result, it is also possible to test roller bearing cages in which the peripheral edges (in particular in comb cages with cover and bottom) have very different rigidity, for example due to their cross section.

The invention will be explained in more detail below with reference to an embodiment with reference to the accompanying drawings. Show it: 1 shows a test device according to the invention in perspective

View,

FIG. 2 shows the test device according to FIG. 1 in longitudinal section along the vertical main plane,

Figure 3 shows the detail X of Figure 2 and

4 shows a Wöhler diagram in which for various materials the number of cycles achieved at the respective test force F _{0 is} plotted.

Figures 1 and 2 show in perspective view and in longitudinal section a test device with two receptacles 1, 2. The receptacle 1 has a bar 3. This is connected via screws 5, 6 with a head piece 7. The head piece 7 has clamping jaws 8, 9, between which an end 10 of a leaf spring 11 shown only in FIG. 2 is clamped. In the device, a test piece 12 is clamped. The test object consists of a sector 13 of a roller bearing cage, which has on both sides of a side wall 15 and 16 (not visible), between which two cage webs 18, 19 extend in the axial direction 20 of the roller bearing cage.

The cage webs 18, 19 have concave contour surfaces 22, 23; 24, 25 (Figure 2), which correspond to the shell contour of a not shown in the figures rolling cylindrical roller body. The rolling element is located in the assembled rolling bearing in the cage pocket 28 formed between the webs 18 and 19.

The cage web 18 is with its upper contour surface 22 in contact with a position adjustable, strip-shaped element 30. The element 30 has a contact portion 31 which is convex and is at least partially in contact with the concave contour surface 22 in areas. By rotation of the Screws 5 and 6, the bar 3 is raised to the clamping of the web 18 and clamped by locking the nuts.

In a corresponding manner, the cage web 19 is fixed. For this purpose, the second receptacle 2 in a mirror-symmetrical configuration has a bar 4 with an integral contact area 41. The strip 41 is in surface contact with the concave surface 24 of the cage web 19. With the bar 4 is connected via the screws 44, 45, a foot piece 46 which carries the jaws 48, the (Figure 2) one end 50 of a leaf spring 51 clamp. At the other end of the spring 51, an unillustrated force transducer may be mechanically connected. The foot piece 46 has, in a manner corresponding to the head piece 7, a bore with a screw 54 which ends in a position-adjustable element 55 with a convex contact surface 56. This contact surface 56 is in contact with the concave surface 25 of the second cage web 19. The element 55 is clamped by cooperation of the screw 54 with a thread 58 in the vertical direction 33.

As FIG. 2 shows, the highest point of the strip 4 in the cage pocket 28 lies in the center of the pull axis and the two screws 5, 6.

Figure 3 shows the detail X of Figure 2 in an enlarged view, in which the cooperation of the concave contact surfaces 22, 23 of the web 18 with the corresponding convex surfaces 31 of the element 30 and the convex curvature of the axially extending web-shaped longitudinal strip 3 can be seen.

The method for testing the test piece 12 proceeds as follows: The clamped test piece 12 is set into vertical oscillation by exciting the foot piece 46 via the leaf spring 51 whose other end is connected to a drive device 58, which is only schematically indicated in FIG. The drive device is a so-called hydropulser, which, by means of a corresponding hydraulic actuation, produces vertical oscillation motion. executes. As indicated by the double arrow 60, this vibration causes alternately a test force in the printing direction 61 and tension 62. The tensile or compressive load of the cage webs 18, 19 acts due to the cooperating concave or convex surfaces (Figure 1) in the tangential direction 63rd , 64.

The leaf springs 11, 51 transmit the compressive or tensile force 61, 62 and thereby allow a tilting of the headstock 7 and the foot piece 46. This also rolling bearing cages with different stiffness of their side edges 15, 16 (Figure 1) are tested (for example comb cages with different cover and floor cross sections or stiffnesses).

The drive device 58 preferably generates a sinusoidal dynamic load in the compression and tension direction 61, 62, which ensures reliable testing of any riveted connections. This type of loading ensures that loosened rivet connections are recognized because a play-preventing tensile load does not permanently rest on the rivet connections. The force component in the pressure direction 61 is dimensioned significantly lower than in the pulling direction 62, as a result of which, advantageously, a failure and thus an end of the test run always results from the tensile force component.

FIG. 4 shows, over the logarithmically plotted number of cycles, the test force F ₀ in the pulling direction in kN for different cage materials, namely bronze and brass with a sinusoidal pulse load and a test frequency of 25 Hz. The force value in the pressure direction 61 is selected to be 0.5 kN lower. It can be seen that with comparatively little effort (at a test frequency of 25 Hz on average 1 measuring point per day can be generated) a partial range of the meaningful Wöhler line can already be generated with approx. 8 measuring points by varying the test force F ₀ . With the method according to the invention a reliable and reproducible statement about the Prüfkraftabhängige life or resilience of rolling bearing cages is possible in a simple manner, which advantageously isolated these parameters from influences of the other rolling bearing components and thus walzzlagerkäfig-individually obtained.

LIST OF REFERENCE NUMBERS

1, 2 shots

3 bar

4 bar

5, 6 screws

7 head piece

8, 9 clamping axes

10 end

11 leaf spring

12 test piece

13 sector

15 upper edge piece

16 lower edge piece

18, 19 cage bars

20 axial direction

22, 23 contour surfaces

24, 25 contour surfaces

28 cage pocket

30 position adjustable element

31 contact area

33 vertical direction

34 screw

35 thread

40 plate

41 contact area

44, 45 screws

46 foot piece

48 jaws

50 end of the leaf spring 51st

51 leaf spring

54 screw position adjustable element

contact area

driving means

double arrow

print direction

tensile direction

test load

Claims

claims

1. Method for testing roller bearing cages with cage webs,

- In which two cage bars (18, 19) between receptacles (1, 2) are clamped, the (22, 23, 24, 25) of the cage bars (18, 19) adapted contact surfaces (31, 56), in which a test force acting on the cage webs (18, 19) is introduced via the receptacles (1, 2) and

- In which the test force is directed and dimensioned so that a varying tensile load (62) on the respective cage web (18, 19) is exercised.

2. The method according to claim 1,

- In which the test force is directed and dimensioned so that alternately a compressive and tensile load (61, 62) on the cage webs (18, 19) is exercised.

3. The method according to claim 1 or 2,

- In which as the test piece (12) is separated from the roller bearing cage sector (13) with at least two cage webs (18, 19) is used.

4. The method according to claim 1, 2 or 3,

- In which the test force is generated by a uniaxial Hydropulser (58).

5. The method according to any one of the preceding claims,

- In which a test force is used, which causes a sinusoidal alternating load (61, 62) of the cage webs (18, 19).

6. The method according to any one of the preceding claims, - in which the tensile load of the cage webs (18, 19) is set higher than the pressure load.

7. The method according to any one of the preceding claims,

- In which the tensile or compressive loads are set so that there is a load cycle number of approximately 10 ⁶ load cycles.

8. testing device for carrying out the method according to one of claims 1 to 7,

- With two receptacles (1, 2) for tensile and / or pressure force transmitting the recording of each one cage web (18, 19),

- Wherein the receptacles (1, 2) contact areas (31, 56) which are adapted to the shape of the cage web (18, 19) or adaptable, and

- with a drive means (58) acting on the receptacles (1, 2) for the dynamic, varying loading of the cage webs (18,

19).

9. Testing device according to claim 8,

- Wherein the receptacles (1, 2) of strips (4, 30, 41, 55) are formed, between which a cage web (18, 19) can be clamped.

10. Testing device according to claim 8 or 9,

- Wherein the receptacles (1, 2) each have a strip (3, 4) for clamping the respective cage web (18, 19).

11. Test device according to claim 8, 9 or 10,

- Wherein at least one receptacle (1, 2) via an elastic element (11, 51) with the drive means (58) is connected, which allows an elastic movement of the receptacle (1, 2).