FR3044092A1 - TEST BENCH FOR BEARINGS SIMULATING A CENTRIFUGAL EFFECT - Google Patents

Abstract

The invention relates to a test bench for testing a turbomachine bearing (7), comprising a support arm (14a-14b), arranged to hold the bearing (7) along a first axis (Y ') connected to said arm, and means (24-22-25-16) for rotating the bearing (7) about said first axis (Y '), characterized in that said arm (14a-14b) is rotatable about a second axis (X '), fixed relative to a platform (10) and spaced apart from the bearing (7), and in that it comprises means (21-20) for rotating the support arm (14a-14b) around said second axis (X '). It also relates to a test method centrifugation of the bearing.

Description

Test bench for bearings simulating a centrifugal effect Field of the invention

The present invention relates to the field of test means for testing turbomachine components operating in a rotating reference system by simulating the effects of the centrifugal force field. It relates more particularly to test means for bearings driven in a rotating reference system.

State of the art:

Double flow turbomachines, especially those having a high dilution ratio, generally comprise an epicyclic gearbox to drive the fan. In a schematic manner, such a turbomachine comprises a fan placed generally in front of the engine part of the turbomachine which successively comprises a gas generator and a power turbine. The purpose of the epicyclic gearbox is to convert the so-called rapid rotational speed of the power turbine shaft into a slower rotational speed for the shaft driving the fan.

For this, with reference to FIG. 1, an example of a gearbox 1 with an epicyclic gear train comprises, with respect to the longitudinal axis X of the turbomachine around which the shaft 2 of the power turbine and the shaft rotate. 3 of the fan: a sun gear 4, in the form of a toothed wheel which is mounted by a splined connection on the turbine shaft 2, rotating in a direction of rotation by driving the gearbox, a carrier 5 secured to the shaft 3 of the fan, on which satellites 6 (three of which are shown arranged here at 60 ° from each other) are mounted by bearings 7, so as to rotate about Y axes related to the carrier 5 , the satellites 6 being formed by toothed wheels meshing around the sun gear 4, and an outer ring gear 8, which meshes with the satellites 6 and which, here, is held fixed with respect to the structure of the turbomachine.

Referring to Figure 2, where a single satellite 6 is schematically shown, during operation of the turbomachine, the sun gear 4 is driven at a rotational speed determined by the turbine shaft 2. By meshing both on the rotating planet gear 4 and on the fixed outer ring gear 8, the satellites 6 are rotated at a speed ω2 around the Y axis of their bearing 7 and drives the planet carrier 5, shown in FIG. FIG. 2 by the hub which supports the bearing 7, in a rotation at a speed ω3 around the X axis. The rotation speeds ω 2 of the satellites 6 and the reduction ratio between the rotation speed ω 3 of the planet carrier 5 and that of the sun gear 4, are determined in particular by the proportions between the radius R! of the sun gear 4 and the R2 rays of the satellites 6.

The number of satellites 6 influences, meanwhile, the forces transmitted through the bearings 7 to change the power of the shaft 2 of the power turbine to the shaft 3 of the fan. Several technologies can be used for the bearings 7, such as, for example: hydrodynamic bearings or plain bearings; cylindrical roller bearings with several rows of rolling elements; or spherical bearings with one or more rows of rolling elements. Generally, although the fan rotates less quickly than the turbine, the rotation speed ω 2 of the planet carrier 5 can be high, of the order of two thousand to four thousand revolutions per minute, so the centrifugal acceleration field created at The level of the bearings 7 can be significant, of the order of 1000 G or even higher, and have significant effects on the bearings 7. On the one hand, in the epicyclic gear train, the bearing 7 of a satellite 6 rotating with the planet carrier 5 is subjected to a very large load N which is substantially oriented in the radial direction and which tends to move them away from the axis X of the gearbox. To this is added a tangential load Nt, due to the transmission of the torque supplied by the turbine shaft 2, which results from the meshing forces of the satellite 6 on the sun gear 4 and the outer ring 8. This results in a loading. overall Ntot in a direction generally inclined relative to the radial direction.

The above-mentioned bearing technologies make it possible to support the forces created by this global loading, but their internal operation is also modified by the presence of the centrifugal forces induced by the rotation ω3 of the planet carrier 5 around the X axis.

Indeed, the centrifugal acceleration field due to the speed ω3 of the planet carrier 5, represented for example by the vectors G1 and G2 in FIG. 2, also acts on the internal elements of the bearing 7, such as the lubricant, the rolling elements and rolling cages, for a rolling bearing, or the oil film for a sliding bearing.

Test benches are known, such as those developed by SNTK for applying a transverse force on a bearing rotating in a fixed reference by means of a jack. This type of means makes it possible to simulate the global loading Ntot but it can not simulate the effects of the centrifugal field on the internal elements of the bearing.

It would be possible, to represent the desired effects on stage 7, to perform a test on the complete gearbox 1. However, in this case, it does not isolate the bearing 7, so we can not extract the performance of the bearing 7 of the entire gearbox 1. In addition, this type of test requires the design and realization of many parts which is expensive and presents more risks.

There is therefore a need to find a test architecture sufficiently simple and efficient, to test a bearing for use in an installation, including a planetary gear reducer, placing it in a rotating frame, applying the Centrifugal force field present in the installation.

DESCRIPTION OF THE INVENTION For this purpose, the invention relates to a test bench for testing a turbomachine bearing, comprising a support arm, arranged to maintain the bearing along a first axis connected to said arm, and means for setting in rotation of the bearing around said first axis, characterized in that said arm is rotatable about a second axis, fixed relative to a platform and spaced apart from the bearing, and in that it comprises means for rotating of the support arm around said second axis.

By adjusting the speed of rotation of the first axis about the second axis and by adjusting the distance from the bearing to the second axis, it is possible to test the bearing in a centrifugal field which has the same characteristics as that of its use, on a carrier. satellites in an epicyclic gearbox for example.

Advantageously, the means for rotating the bearing about the first axis comprise a first gear, centered on the first axis and connected to an outer portion of the bearing rotating about said first axis, and a second gear, centered on the second axis. and independent of the support arm, the first gear and the second gear being arranged to mesh with one another.

The drive mode provided by the gearing of the two gears makes it possible to adjust the speed of rotation of the bearing around the first axis, the speed of rotation of the rotating arm being fixed at a value determining the centrifugal field, by acting on the ratio between the rotational speed of the support arm and the speed of rotation of the toothed wheel.

Moreover, by adapting the mass of the first gearwheel, linked to the external part of the bearing, it is possible to adjust the centrifugal forces to which the bearing is subjected on the test stand to reproduce the overall level of loading in the gearbox, even if the application direction is a little different. On the other hand, the fact that the second gear wheel is independent of the support arm allows a simple assembly, in particular to adjust the parameters representative of the centrifugal field independently of those of the rotation of the bearing.

Advantageously, the second gear wheel is rotated about the second axis by means independent of the means for rotating the support arm.

Advantageously, the test bench comprises means for measuring a torque transmitted by a motor for rotating the second toothed wheel and a torque transmitted by a motor for rotating the support arm.

Preferably, in particular to represent the use of a satellite bearing in an epicyclic reduction gearbox, the first axis and the second axis being substantially parallel. The invention also relates to a method for testing a bearing intended to be used in a rotating reference system, in particular in a turbomachine epicyclic gear train, in which the bearing is rotated around a first axis on which it is centered, characterized in that the first axis is rotated about a second axis and at least the following three parameters are determined, the distance between the bearing and the second axis, the rotational speed of the bearing around the first axis and the rotational speed of the first axis about the second axis, so as to represent the conditions of use of said bearing.

Preferably, the method comprises a step in which a rotating mass value is adjusted with the bearing around the first axis, so as to represent the conditions of use of said bearing.

The mass being eccentric with respect to the second axis, it undergoes the centrifugal field created by the rotation of the support arm and exerts a force on the bearing, fixed in the reference of the axis of the bearing. This effort makes it possible to reproduce the level of loading that is applied to the bearing when it is used, for example on a planet carrier in an epicyclic gear reducer.

Advantageously, a test bench as described above is used to implement the method.

The method may comprise a step in which the speed of rotation of the bearing and the speed of rotation of the first axis are regulated by controlling respectively first and second rotary motors, independent of one another.

Advantageously, the method comprises a step in which torques transmitted by said motors are measured to means for rotating the bearing and the first axis, so as to evaluate the power losses due to the bearing.

Brief description of the figures:

The present invention will be better understood and other details, features and advantages of the present invention will emerge more clearly on reading the description of a nonlimiting example which follows, with reference to the appended drawings, in which: FIG. perspective, an exploded view of a planetary reduction gear comprising bearings to be tested with a test bench according to the invention; FIG. 2 schematically represents in cross section the conditions to be reproduced for the tests of a bearing used in a gearbox such as that of FIG. 1; Figure 3 schematically shows a test bench according to the invention in side view; Figure 4 schematically shows the test bench of Figure 3 in front view; and FIG. 5 shows the relationships between the movements of the main elements of the test bench of FIGS. 3 and 4.

Description of an embodiment:

Figures 1 and 2 have already been discussed in the foregoing.

With reference to FIGS. 3 and 4, a test bench according to the invention comprises the elements described below.

It comprises firstly a fixed platform 10 to support the rotating elements. Here, a first pair of uprights 11a, 11b which extend perpendicularly to the platform 10 and are pierced with two circular orifices placed facing each other, centered around an axis X 'parallel to the platform 10 and having substantially the same radius.

Preferably, it also comprises a second pair of uprights 12a, 12b, which extend perpendicular to the platform 10 on either side of the uprights 11a, 11b of the first pair along the axis X ', on the outside . The amounts 12a, 12b of the second pair are also pierced with two circular orifices centered around the axis X '. They have the same radius, which can be smaller than that of the orifices of the uprights of the first pair.

The test bench further comprises a centrifugation module 13, placed between the two uprights 11a, 11b of the first pair and centered on the axis X '. The centrifugation module 13 here comprises two parallel side plates 14a, 14b, centered around the axis X ', between which is installed a bearing 7 to be tested, shown in broken lines in FIG.

For example, the bearing to be tested is the bearing 7 used in the gearbox 1 presented in the introduction. It comprises, extending around an axis Y ', which is here substantially parallel to the axis X', an inner ring and an outer ring rotating around the inner part.

The inner ring is installed on a shaft 15 fixed to the side plates 14a, 14b. The side plates 14a, 14b comprise means 17 for fixing each one axial end of the barrel 15. Preferably, these means 17 are fixed for example on a slide, not shown, extending radially with respect to the axis X ' . In this way, one can move the bearing 7 and adjust the distance Rp of its axis Y 'relative to the axis X'.

A toothed wheel 16 is mounted on the outer ring of the bearing 7. Advantageously in this case, the toothed wheel 16 has a mass M generally greater than the mass of the satellite 6. This upper mass makes it possible to simulate the totality of the force applied to the bearing in the gearbox 1 presented in introduction. The toothed wheel 16 also has an external radius Rs determined. The wheel and the outer ring of the bearing can form a single piece.

The side plates 14a, 14b also comprise means placed symmetrically with respect to those of the bearing 7 to be tested to carry a counterweight 18 whose mass is determined to be equal to that of the entire bearing 7 to be tested and the toothed wheel 16, with a substantially identical size. In this way, the entire centrifugation module 13 with the bearing 7 to be tested is dynamically balanced around the axis X '.

The centrifugation module 13 is thus configured, the side plates 14a, 14b form a first arm, bearing the bearing 7 on the axis Y 'at a distance Rp from the axis X', and a second arm carrying the counterweight 18 in the opposite direction with its center of gravity situated at the same distance Rp from the axis X '.

The centrifugation module 13 also comprises a hollow shell extending from the outside of a first lateral plate 14a and mounted in the orifice of a first upright 11a of the first pair by a bearing 19a, for example with bearings, and a hollow shell extending from the outside of the second side plate 14b and mounted in the orifice of the second upright 11b of the first pair by another bearing 19b. Here, the first ferrule passes through a first upright 11a of the first pair, so as to comprise a toothed wheel 20 enabling the centrifugation module 13 to be driven in rotation by a dedicated motor 21, according to a rotation speed ωρ that can be adjusted .

The test bench also comprises means for driving the toothed wheel 16 fixed to the outer ring of the bearing 7 to be tested. For this, in the example presented, a shaft 22 centered on the axis X 'passes through the centrifugation module 1 passing inside the rings and being held in the circular orifices of the uprights 12a, 12b of the second pair by bearings 23a, 23b. A dedicated motor 24 makes it possible to adjust the speed ω 0 of rotation of the shaft 22 independently of the value ωρ of the speed of rotation of the centrifugation module 13.

In addition, a toothed central wheel 25 is mounted on the central shaft 22 in the free space between the two lateral plates 14a, 14b of the centrifugation module 13. The radius Rc of this central wheel 25 and its teeth are arranged in such a way as to it meshes with the toothed wheel 16 integral with the outer ring of the bearing 7 to be tested. In this way, it drives the toothed wheel 16 and the bearing 7 to be tested in rotation about the axis Y 'at a speed ω3 which is a function of the rotational speed u) c of the central shaft 22, of the rotation speed ωρ of the centrifugation module 13 and the ratio between the radii Rs and Rc respectively of the toothed wheel 16 integral with the bearing 7 and the central wheel 25.

For a given geometry of the test bench, it is therefore possible to vary the value ω3 of the speed of rotation of the outer ring of the bearing 7 independently of the rotation speed ωρ of the centrifugation module 13 by varying the value u) c the speed of rotation of the central shaft 22. Comparing FIGS. 5 and 2, it can be seen that the positioning geometry of the bearing 7 in the gearbox 1 can be reproduced on the test bench by adjusting the distance Rp between the axes X 'and Y' at the value R3 taken in the gearbox. It is also seen that the speeds ω3 and ωρ of rotation of the bearing 7 and the centrifugation module 13, on the test bench, can reproduce the values ω2 and ω3 of the rotation speeds of the satellite 6 and the planet carrier 5 in the gearbox 1. However, on the test bench, the ratio between the speeds ω3 and ωρ is set as described above, whereas, in the gearbox 1, the rotation speed ωι of the sun gear 4 being given, it is the rolling of the satellite 6 on the sun gear and the outer ring 8 which determines the rotation speed ω 3 of the planet carrier and the rotation speed ω 2 of the satellite 6 about its axis Y.

The test bench has been presented with axes X 'and Y' substantially parallel, to represent the geometry of the gearbox 1 presented as an example in the introduction. If necessary, an alternative embodiment, the axis Y 'around which the bearing 7 rotates in the centrifugation module 13 could be slightly oblique with respect to the axis X' of the centrifugation module, using bevel gears between the wheel 25 and the toothed wheel 16 fixed to the bearing 7.

Preferably, the test bench according to the invention also comprises means, not shown in the figures, arranged to measure the torques exerted by each motor 21, 24 respectively on the shaft of the centrifugation module 13 and on the shaft. 22. These measuring means are advantageously made by torque measuring instruments known to those skilled in the art that can be installed at the output of the engines.

Setting the rotation speed ω8 of the bearing 7 by the ratio between the rotation speeds ω0, ωρ of the central wheel 23 and the centrifuging module 13 by adjusting the independent adjustment of the speed of the two motors 21, 24, allows to limit the gears on the test bench. A calculation of the power losses due to the bearing 7 from the pairs measured at the output of the two motors 21,24 is thus more precise.

Advantageously, the test bench also comprises a lubrication system, not shown, which makes it possible to introduce oil inside the axis of the bearing from a fixed installed reservoir on the platform 10 thanks to a rotary joint system for passing the oil from the fixed reference to the rotating reference of the centrifugation module 13. In this way, such a lubrication system may comprise means arranged to adjust the oil flow and reproduce the lubrication mode real level 7 to test.

With such a test bench, a test procedure for a bearing 7 intended to operate in the gearbox 1 described in the introduction, for example, advantageously comprises the steps described below.

In a first step, the two parameters are defined for controlling the centrifugal acceleration field that will be applied to the stage 7 on the test bench, so as to reproduce that in which the bearing 7 in the gearbox 1 would be located in Working conditions. These two parameters are the distance Rp from the axis Y 'to the axis X' and the rotational speed ωρ of the centrifugation module 13: the distance Rp from the axis Y 'to the axis X' can be set as soon as possible. this first step so that it is equal to the distance R3 of the Y axis to the X axis in the gearbox 1 by adjusting the position of the fastening means 17 of the drum 15 on the rails of the side plates 14a, 14b of the centrifuge module 13; the speed of the first motor 22 can be controlled during the tests so that the rotation speed ωρ of the centrifugation module 13 takes the value ω3 of the speed of rotation of the carrier 5 in a chosen operating regime.

In a second step, the parameters are defined which make it possible to control the speed of rotation ω3 of the bearing 7, so as to reproduce the values ω2 taken under operating conditions of the gearbox 1. Two parameters control this speed of rotation ω3 of the bearing 7 for a given rotation speed ωρ of the centrifugation module 13, the rotational speed ω0 of the central shaft 22 and the reduction ratio between the central wheel 25 and the toothed wheel 16 connected to the outer ring of the bearing: in view of the the distance Rp set in the previous step for the position of the Y 'axis of the bearing 7, a choice can be made from this step for Rc and Rs rays respectively of the central wheel 25 and the toothed wheel 16 connected to the bearing 7, so that they mesh and provide a reduction ratio compatible with the speeds of rotation that can provide the second motor 24; The central wheel 25 having the diameter Rc determined by this calculation can be installed on the test bench at this stage; the speed of the second motor 24 can be controlled during the tests so that the rotation speed ω3 of the bearing 7 takes the value ω2 of the speed of rotation of the bearing 7 in a chosen operating regime.

In a third step, the mass M is defined in rotation with the bearing 7 which must allow to find the loading level Ntot in force applied to the bearing in the reducer. The mass must be calculated taking into account the speed of the selected arm. Having determined the radius Rs of the toothed wheel 16 during the previous step, it is possible during this third step to directly produce a toothed wheel 16 of radius and determined mass M, or to adjust the mass of a toothed wheel of radius Rs, for example by fixing him cylindrical tails adapted to reach the determined mass M.

A fourth step consists in mounting the bearing 7 with its toothed wheel 16 on the centrifugation module 13. During this step, the counterweight 18 is also mounted at the right distance, on the radially opposite side of the centrifugation module.

A fifth step comprises the tests themselves, which are carried out by controlling the rotational speeds of the first 21 and the second 24 engine so as to obtain rotational speeds ωρ and ω3 of the centrifugation module 13 and the bearing 7 respectively representative rotational speeds ω3 and ω2 of the planet carrier 5 and the bearing 7 in the gearbox 1 in operation. Advantageously also, the lubrication system is started during this step to reproduce the lubrication conditions in use.

The torques transmitted by the first 21 and the second motor 24 are measured over the course of the tests carried out in this step. These measurements make it possible to evaluate the power losses due to stage 7 as a function of gearbox speeds and its duration of use. Moreover, the evolution of the power losses over time and / or visual observations of the bearing 7 after dismantling can make it possible to evaluate its wear as a function of its duration of use.

Claims (10)

claims A test bench for testing a turbomachine bearing (7), comprising a support arm (14a-14b), arranged to hold the bearing (7) along a first axis (Y ') connected to said arm, and means (24-22-25-16) for rotating the bearing (7) around said first axis (Y '), characterized in that said arm (14a-14b) is rotatable about a second axis (X '), fixed relative to a platform (10) and spaced apart from the bearing (7), and in that it comprises means (21-20) for rotating the support arm (14a-14b) around said second axis (X '). 2. test bench according to the preceding claim, characterized in that the means for rotating the bearing (7) about the first axis (Y ') comprise a first gear (16), centered on the first axis (Y ') and connected to an outer part of the bearing (7) rotating about said first axis (Y'), and a second gear (25), centered on the second axis (X ') and independent of the support arm (14a-14b ), the first gear wheel (16) and the second gear wheel (25) being arranged to mesh with one another. 3. test bench according to the preceding claim, characterized in that the second gear (25) is rotated about the second axis (X ') by means (24-22) independent means (21-20) rotating the support arm (14a-14b). 4. test bench according to the preceding claim, characterized in that it comprises means for measuring a torque transmitted by a motor (24) for rotating the second toothed wheel (25) and a torque transmitted by a motor (21) for rotating the support arm (14a-14b) 5. Test bench according to one of the preceding claims, wherein the first axis (Y ') and the second axis (X') are substantially parallel. 6. A method of testing a bearing (7) intended to be used in a rotating reference system, in particular in a turbomachine epicyclic gearbox, in which the bearing (7) is rotated about a first axis ( Y ') on which it is centered, characterized in that the first axis (Y') is rotated about a second axis (X ') and at least the following three parameters are determined: the distance (Rp) between the bearing (7) and the second axis (X '), the rotational speed (ω5) of the bearing (7) around the first axis (Y') and the rotational speed (ωρ) of the first axis ( Y ') about the second axis (X'), so as to represent the conditions of use of said bearing (7). 7. Method according to the preceding claim, comprising a step in which a rotating mass value is adjusted with the bearing (7) around the first axis (Y '), so as to represent the conditions of use of said bearing (7). 8. Method according to one of claims 6 or 7, wherein using a test bench according to one of claims 1 to 5. 9. Method according to the preceding claim, comprising a step in which the speed of rotation (ωδ) of the bearing (7) and the speed of rotation (ωρ) of the first axis (Y ') are adjusted respectively by controlling a first (25) and a second (21) rotating motor, independent of each other. 10. Method according to the preceding claim, comprising a step in which torques transmitted by said motors are measured to means for rotating the bearing (7) and the first axis (Y '), so as to evaluate power losses due to at the landing (7).