JP7519764B2 - Ball bearing, a unit for measuring friction torque under load, provided with said bearing, and a test bench for rotating devices provided with said unit for measuring - Google Patents

Description

The present invention relates to the field of ball bearings, more specifically to their use in units for measuring friction torque under load. The present invention further relates to the field of test benches, more specifically to test benches designed to measure the friction torque of rotating devices, in particular bump stop devices for motor vehicles.

In a known manner, a vehicle suspension system comprises a strut supporting the axle and wheel of the vehicle. A bump stop is arranged on the top of the strut, opposite the wheel and the road surface, between the suspension spring and an upper member fixed to the vehicle body. The spring is arranged around a damping piston rod, the end of which can be fixed to the vehicle body.

The bump stop comprises a bearing, a lower spring retainer, an upper spring retainer, and at least one gasket seal disposed between the two spring retainers. The various components of the bump stop may be made of plastic material, and the spring retainer may be reinforced by a rigid insert, particularly made of metal, to increase its mechanical strength. The upper spring retainer is inserted between the upper ring of the bearing and the upper member, while the lower spring retainer is inserted between the lower ring of the bearing and the suspension spring. Thus, the bump stop allows the transmission of axial forces between the suspension spring and the body of the vehicle, while allowing relative angular movement between the rings of the bearing.

The central axis of the bump stop and the central axis of the strut with the spring may be inclined relative to each other, and the relative inclination of the axes can be between 5° and 10°. The bump stop is therefore subjected to the resulting radial force.

Apart from its performance in terms of mechanical strength and sealing, an important factor in the quality of a bump stop is its friction torque under load. It is important to verify this mechanical property of a bump stop, since it affects the suspension performance of the vehicle in which it is installed, in addition to its driving comfort. Test benches designed to measure the friction torque of bump stops under load have been developed in order to optimize their structure, materials and design. These test benches must provide test conditions close to the application conditions.

In a known manner, a test bench for measuring the friction torque of bump stops under load comprises a tubular sleeve provided with a cylindrical bore in which two bump stops are mounted from top to bottom, each bump stop being mounted at one of the axial ends of the bore. Each of the fixed spring retainers of the bump stops is fixed in the bore. The rotationally movable spring retainers of the bump stops are rotationally connected by a shaft, which applies a load to the bump stops. The bore extends around a central axis along a given angle inclined to the horizontal, the central axis being along an angle characteristic of the relative inclination between each bump stop and the shaft simulating a strut. A rotationally oscillating movement about the central axis is imparted to the shaft by a motor, which movement is transmitted to the two bump stops to be tested.

Such a test bench is therefore capable of testing the bump stops under conditions of rocking, tilting, axial load, and radial load (due to the determined tilt and applied axial load) close to the applied conditions. The test bench is also provided with at least one friction torque sensor for measuring the friction torque due to the rocking of the two bump stops. The two related bump stops for measuring the friction torque may be identical or different, one bump stop under test and the other bump stop with known characteristics.

The friction torque of a bump stop tested in such a test bench is significantly influenced by the load to which the bump stop is subjected. Moreover, this problem does not only arise for the characterization of the friction torque of a bump stop under load, but also for the characterization of any rotating device having application conditions under load. It is therefore desirable to provide a test bench with a unit for measuring the friction torque under load, which ensures reliable and reproducible measurements.

Furthermore, any system that rotates and is subject to axial loads, particularly bump stops used in automobiles or tested in test benches, but also other types of bearings such as clutch bearings/clutch release bearings, are subject to the problem of movement of the bearing position between loaded and unloaded positions. Such rotating systems may be coupled to a rotating shaft and subject to axial loads. Such shafts are generally mounted in a fixed housing, with at least one bearing interposed between the shaft and the housing to support the shaft during rotational movement.

In this type of application, the bearing comprises an inner ring fixed to the shaft and having a bearing track formed by a recessed groove, an outer ring mounted in the housing and having a bearing track formed by a recessed groove, and at least one row of balls between the bearing tracks of the two rings to support their relative rotation. To allow the bearing to follow the axial movement of the shaft, it is known to mount the outer ring of the bearing in a fixed housing without adjustment.

However, the rings may have a non-optimized relative position, especially with misalignment in the radial plane. Contact between the balls and the bearing track may be part of the axial load that can be transferred from the shaft to the bearing at a certain angle. Furthermore, additional friction torques may be generated by the bearing acting on the rotation torque of the shaft and thus of the rotating system. It is therefore desirable to provide a bearing suitable for applications with rotating systems and for test benches under load, in particular with a unit for measuring the friction torque under load.

The present invention aims to provide a ball bearing capable of supporting a rotating and loaded device, which does not have the aforementioned drawbacks, which can in particular be used in a unit for measuring the friction torque of a loaded rotating device, such as a bump stop, which is capable of reproducing the application conditions, is suitable for any type of rotating device and provides highly reliable and reproducible measurements.

The present invention relates to a ball bearing comprising a first ring provided with a first bearing track and a second ring provided with a second bearing track, the two rings being concentric and rotating relative to one another about a central axis, the ball bearing comprising a row of balls mounted radially between the first and second bearing tracks.

According to the present invention, the first bearing track is a recessed annular groove formed on the face of the first ring, and the second bearing track is a cylindrical surface of the second ring.

According to the invention, the axial movement of the first ring drives balls housed in grooves forming a first bearing track, which slide axially on a cylindrical surface forming a second bearing track of the second ring. Whatever the relative radial position between the first and second rings, the bearing between the balls and the rings is optimized without introducing additional frictional torque.

Further advantageous but non-mandatory features of the ball bearing can be implemented individually or in combination.
To support the balls in the circumferential direction, the bearing is equipped with a cage.
- the first ring is an inner ring provided with a bore and an outer cylindrical surface, the first bearing track being a recessed annular groove formed on the outer cylindrical surface, the second ring is an outer ring provided with an outer surface and a cylindrical inner bore, the second bearing track being formed by the cylindrical inner bore.
- the first ring is an inner ring provided with a bore and an outer cylindrical surface, the first bearing track being formed by the outer cylindrical surface, the second ring is an outer ring provided with an outer surface and a cylindrical inner bore, the second bearing track being a recessed annular groove formed on the cylindrical inner bore.
- The inner ring rotates.
- The outer ring is non-rotating.

According to a further feature, the present invention relates to a unit for measuring the friction torque of a rotating device under load, comprising a torque sensor.

The measuring unit comprises a shaft, the first end of which is designed to be coupled to a rotating device. The measuring unit comprises a tubular housing with a central bore and fixed to the face of the plate, the shaft extending through the plate and into the bore of the housing.

The unit for measuring also comprises at least one bearing according to any one of the previous embodiments, which is inserted between the bore of the housing and the shaft to support the shaft in a rotary motion. The bearing comprises an inner ring fixedly mounted on the shaft, an outer ring fixedly mounted in the housing, and a row of balls arranged between a first bearing track on one of the two rings and consisting of a concave annular groove formed on the surface, and a second bearing track on the other ring and consisting of a cylindrical surface.

The unit for measuring comprises a measuring plate arranged in the housing, the measuring plate having a first surface connected to the second end of the shaft by means of an Oldham coupling, whereby the shaft transmits torque only to the measuring plate, the measuring plate and the shaft having a shape corresponding to the Oldham coupling, and the measuring plate having a second surface cooperating with the torque sensor. The stop is inserted between the second end of the shaft and the first surface of the measuring plate, the stop comprising a first ring fixed to the first surface of the measuring plate, a second ring fixed to the second end of the shaft, and at least one row of rolling elements inserted between the two rings, the row of rolling elements radially surrounding the Oldham coupling.

Thus, the shaft of the unit for measuring, which rotates and is loaded, is supported by the ball bearing according to the invention. When the shaft is not loaded, the components of the ball bearing are in given positions, each of which contributes to the rotation of the shaft. When the shaft is loaded, it is displaced axially. The inner ring of the bearing follows this axial displacement, while the outer ring remains stationary in the housing. During the relative axial movement of the rings of the bearing, the balls slide axially on the cylindrical surface of the second bearing track, which are axially held in the first hollow bearing track and are not axially restricted relative to the second cylindrical bearing track. By using the invention, the bearing does not create an additional friction torque, and the torque measured by the unit for measuring is the torque of the rotating device. Moreover, the residual part of the axial load is not transmitted to the bearing.

Further features of the unit for measuring, which are advantageous but not mandatory, may be employed individually or in combination.
The second face of the measurement plate is provided with a protrusion which is connected to a torque sensor.
The housing has a free end located opposite the shaft and closed by a cover.
The torque sensor is also provided with means for measuring the load.
The unit for measuring comprises a temporary connection between a cover and a housing, the cover being in contact with the torque sensor.
The temporary connecting means comprises at least one screw extending into corresponding holes in the cover and the housing.
The unit for measuring comprises temporary connection means between the measuring plate and the housing, by which the measuring plate is fixed to the housing.
The measuring plate comprises at least one radial projection capable of cooperating with the temporary connecting means and with the housing.
the housing comprises at least one opening in which at least one radial projection of the measuring plate is received;
The temporary connecting means comprises at least one screw extending into corresponding holes in the measurement plate and the housing.

According to a further feature, the invention relates to a test bench for measuring the friction torque of a rotating device, the test bench comprising a first fixed plate, a second plate that is translationally movable and can move towards or away from the first plate, thereby applying an axial load to the rotating device, a test chamber formed between the plates, a drive means fixed to the first plate, a unit for measuring according to any of the aforementioned embodiments of the invention fixed to the second plate, a first support rotatably connected to the drive means, and a second support connected to the unit for measuring, the first support being arranged in the test chamber and designed to be fixed to a first element of the rotating device that is movable in rotation, and the second support being designed to be fixed to a second element of the rotating device.

The invention will be more clearly understood on reading the following description, given by way of non-limiting example, which is given with reference to the accompanying drawings, in which:

FIG. 2 shows a front view of a test bench for bump stop devices, provided with a unit for measuring according to the invention. FIG. 2 is a perspective view showing a side of the test bench of FIG. 1 . FIG. 2 shows a detail of a bump stop device in the test bench of FIG. 1 in an axial section. FIG. 2 is a perspective view showing details of a drive means for the test bench of FIG. 1; FIG. 2 shows a detail of a unit for measuring the test bench of FIG. 1 along the axial section II. 6 shows a detail of a unit for measuring of the test bench of FIG. 5 along the axial section II-II in a first embodiment; 6 shows a detail of a unit for measuring of the test bench of FIG. 5 along the axial section II-II in a second configuration; FIG. 6 shows a bearing for the unit for measuring of FIG. 5 along an axial section.

Figures 1 and 2 show a test bench, generally designated by the reference number 1, for measuring the friction torque of a rotating device 2, in this case a bump stop. For reasons of clarity of description and illustration, the test bench 1 is not shown with a fixed housing that holds the test bench and fixes it to the ground.

The test bench 1 comprises a first lower plate 3. This first plate 3 extends in a horizontal plane, is stationary and is fixed to the housing of the test bench 1.

The test bench 1 comprises a second plate 4, which extends in a horizontal plane, is parallel to the first plate 3 and is movable in translation relative to the first plate 3.

The test bench 1 comprises four tubular guides 5 fixed to a first plate 3 and a third upper plate 7, the third upper plate also being stationary and fixed to the housing. The tubular guides 5 each extend between the first fixed lower plate 3 and the third fixed upper plate 7 along an axis perpendicular to the plates 3, 4 and 7. The tubular guides 5 pass through the second movable plate 4 and each form a guide for the translational movement of the plate 4.

The test bench 1 also comprises a mechanism 6 for the transmission of the mobile body, in this case of the known screw type 8, which contributes to the translational movement of the second plate 4. The transmission mechanism 6 is advantageously fixed to the third plate 7. The second plate 4 can be translated between the first plate 3 and the third plate 7.

The test bench 1 comprises a test chamber 9 formed between a first fixed plate 3 and a second translatable plate 4. The bump stop 2 is designed to be tested on the test bench and is accommodated in the test chamber.

The second plate 4 is translatable to apply an axial load to the bump stop 2 being tested in the test bench 1, as will be described in more detail hereinafter. The second plate 4 remains stationary during the test and is set to translate only during the test condition setup and adjustment phase.

Advantageously, the first plate 3 and the second plate 4 each comprise a layer 3-1, 4-1 of insulating material, which is on the inner surface of the plates, respectively, within the test chamber 9.

According to a variant not shown, the test bench 1 comprises a supporting housing with side walls, which in the test chamber 9 are also covered by a layer of insulating material on their inner surface. The test chamber 9 is therefore insulated. Advantageously, the test bench comprises means (not shown) for regulating the temperature in the test chamber 9, whereby the temperature of the test may be adjusted in order to reproduce the application conditions. It is also possible to provide means for monitoring the humidity measurement in the test chamber 9.

The test bench 1 comprises a drive means 10 fixed to the first lower stationary plate 3 and a first lower support 11 rotatably connected to the drive means 10. The test bench 1 also comprises a unit for measuring 12 fixed to the second upper plate 4 which can be translated, and a second upper support 13 connected to the unit for measuring 12. A bump stop 2 designed to be tested in the test bench 1 is connected on the one hand to the first support 11 and on the other hand to the second support 13.

Figure 3 shows the bump stop 2 mounted in the test chamber of the test bench 1. The bump stop 2, in this illustrated embodiment, is of the MacPherson Suspension Bearing Unit or MSBU type.

The bump stop 2 comprises a single bearing 14 in oblique contact, a rotationally movable lower spring retainer 15, and an upper spring retainer 16. The bump stop 2 and its components have a generally circular symmetrical shape about a central axis X2. The spring retainers 15 and 16 together define an internal housing in which the bearing 14 is housed. The bump stop 2 may advantageously comprise external and/or internal sealing means to provide sealing of the bearing against external contamination.

In this embodiment, the bearing 14 comprises an inner ring and an outer ring, along with a row of rolling elements, in this case balls, arranged with oblique contact between the rings (not shown). The bearing 14 preferably has oblique contact to limit internal forces and friction on the bump stop 2 in use.

The lower spring retainer 15 is rotatable about the axis X2 and relative to the upper spring retainer 16. The lower spring retainer 15 is annular and has a central tubular portion and radial portions extending outwardly from the tubular portion. The lower spring retainer 15 forms a lower support from the first upper axle side for the bearing and a support from the second lower axle side that can cooperate with the strut spring of the vehicle.

In the illustrated embodiment, the first lower support 11 of the test bench 1 comprises a support rod 17 extending along an axis X17, which is inclined to the axis X2 of the bump stop 2 along an angle A17. The support rod 17 comprises a first lower end 17-1, described below, connected to the drive means 10, and a second upper end 17-2 provided with a first adaptation means 18, which is shaped to match the lower surface of the lower spring retainer 15. The first adaptation means 18 of the support rod 17 makes it possible to reproduce the structural and mechanical features of the strut spring of the motor vehicle. The first adaptation means 18 is fixed to the support rod 17 by means of at least one fixing screw 19. The first adaptation means 18 can therefore be easily attached to or detached from the support rod 17, in particular when it is replaced by a differently shaped first adaptation means, which is suitable for the further bump stop to be tested.

Alternatively, the support rod may be replaced by a strut having a spring at its second end, the spring being designed to support against the support surface of the first spring retainer of the bump stop.

The upper spring retainer 16 is annular about the axis X2 and forms an upper support for the bearing 14. The upper spring retainer 16 is generally stationary within the suspension system of the vehicle, the upper spring retainer 16 being fixed to the chassis of the vehicle. The bump stop 2 is mounted on the test bench 1, so that the upper spring retainer 16 is not stationary and can transmit friction torques generated by the rotational and rocking movement of the lower spring retainer 15.

In the illustrated embodiment, the second upper support 13 of the test bench 1 comprises a shaft 20, which is provided with a first lower end 20-1 connected to the upper spring retainer 16 of the bump stop 2 and a second upper end 20-2 connected to a unit 12 for measuring, which will be described below. The second support 13 also comprises a second adapting element 21 fixed to the upper spring retainer 16, which is connected to the first end 20-1 of the shaft 20 by means of a pivot connector 22. The connection between the shaft 20 and the bump stop 2 can therefore accommodate any type of tested bump stop and the inclination of the support rod 17.

Advantageously, the second adapting element 21 comprises a lower part 21-1 fixed to the upper spring retainer 16 and an upper part 21-2 connected to the first end 20-1 of the shaft 20 by means of a pivot connector 22, the two parts 21-1 and 21-2 being fixed relative to each other by means of a fixing screw 21-3. Thus, the lower part 21-1 of the second adapting element 21 can be easily mounted on or removed from the upper part 21-2 and thus the shaft 20, when it is replaced by a second adapting means of a different shape, particularly suited to the further bump stop to be tested.

Alternatively, the bump stop may have a variety of structural designs, and the test bench 1 according to the invention is suitable for receiving and testing any type of bump stop. More specifically, it is sufficient to provide the second end 17-2 of the support rod 17 with a first matching element with a lower spring retainer, and/or the first end 20-1 of the shaft 20 of the second matching element with an upper spring retainer, which can be connected to these elements of the bump stop to be tested.

The first lower support 11 is rotatably connected to the drive means 10. The first support 11 comprises a support rod 17 having a first end 17-1, which is connected to the drive means 10 as shown in FIG. 4.

The first support 11 comprises a guide 23, in which the first end 17-1 of the support rod 17 is connected to a pivot connection 25 by means of a connecting element 24. The guide 23 comprises two lateral rails 23-1 and 23-2, the connecting element 24 comprising a protrusion capable of cooperating with these rails 23-1, 23-2. When the connecting element 24 is placed on the rails 23-1, 23-2 of the guide 23, it is fixed in this desired position by means of fixing means (not shown), for example screws, clamping means or any other temporary fixing means. The rod 17 is thus connected to the guide 23, whereby the angle of inclination of the rod 17 can be determined with respect to the bump stop 2 on the one hand and with respect to the guide 23 on the other hand.

The first support 11 also comprises a support plate 26 rotatably connected to the drive means 10. The guide 23 is fixed from an operational point of view to the support plate 26 by any suitable means, for example by a fixing screw. The rod 17 is thus connected to the drive means 10 by means of a connecting element 24 mounted on the guide 23, which makes it possible to ensure that the rod 17 and the support plate 26 are tilted.

The first support 11 assembly is mounted on a fixed lower plate 3 of the test bench. The support plate 26 is driven by a drive means 10 using a shaft (not shown) passing through an opening in the plate 3.

The drive means 10 is shown in FIG. 1 and comprises a motor 27 on which a drive plate 28 is arranged, which rotates about a rotation axis X28. A connecting rod 29 has a first end connected to the drive plate 28 by a pivot connection 30 and a second end connected to a first end of a crank 32 by a pivot connection 31. The crank 32 has a second end which is rotatably connected to the support plate 26 of the first support 11 by means of a shaft (not shown) passing through the lower plate 3.

In an embodiment of the invention, the drive means 10 is a rod-crank connection of known type, capable of converting a rotational movement into a swinging movement around an axis. The crank 32 transmits this swinging movement to the support plate 26, and by successive connections to the guide 23 with the coupling element 24, to the support rod 17 with the first matching means 18, and finally to the lower spring retainer 15 of the bump stop 2 to be tested in the test bench 1. A test bench 1 equipped with such a drive means 10 makes it possible to reproduce the movements to which the bump stop 2 to be tested is subjected in the assembled state.

On the opposite side of the drive means 10 to which the lower spring retainer 15 of the bump stop 2 is connected, the test bench 1 is provided with a measuring unit 12 connected to the upper spring retainer 16 of the bump stop 2.

More specifically, the upper spring retainer is connected to the unit for measuring 12 by means of a second support 13, which includes a second fitting element 21 connected to a first end 20-1 of the shaft 20. The unit for measuring 12 is shown in Figures 5 and 6 in a first mounting configuration and in Figure 7 in a second mounting configuration.

The measuring unit 12 comprises a tubular housing 33 with a central bore 33-1 extending along a central axis X33 and is fixed to the outer surface of the translatable second plate 4. The housing 33 advantageously comprises a radial edge 33-2 and a number of fixing screws 34 passing through openings formed through said edge 33-2 for fixing in corresponding openings formed in the second plate 4.

The second plate 4 is also provided with a bore 4-2 traversed by a shaft 20 which extends in a bore 33-1 of the housing 33 along an axis X20 concentric with the central axis X33. The shaft 20 thus enables the bump stop 2 to be coupled on one side inside the test chamber 9 to a measuring unit 12 mounted on the opposite side of the second plate 4 outside the test chamber 9.

Two bearings 35, 36 are interposed between the bore 33-1 of the housing 33 and the shaft 20 to support the shaft 20 during rotational movement. In this embodiment, the bearings 35, 36 are similar and only the bearing 36 will be described hereafter and shown in detail in FIG. 8.

The bearing 36 comprises an inner ring 33-2 and an outer ring 33-3 which are concentric and rotate relative to each other about a central axis X33 of the bore 33-1 of the housing 33, and a row of balls 36-1 arranged radially between the rings.

The shaft 20 has a stepped outer surface 20-3, the cylindrical surface on which the inner ring of the bearing 36 is mounted is formed to have a smaller diameter than the central part of the shaft, which has an outer surface with a larger diameter. The inner ring 36-2 has a cylindrical bore 36-4 mounted in a clamped manner on the cylindrical part of the outer surface 20-3 of the shaft 20. The shaft 20 thus has a stepped outer surface 20-3 that allows simple mounting of the bearings 35, 36. A shoulder is formed around the shaft 20 to provide axial support for the inner ring of the bearings 35, 36. Two support rings 37, 38 are fixedly mounted on the shaft 20 to fix the inner ring of the bearings 35, 36 in the axial direction. The support ring 38 is mounted in particular around the second end 20-2 of the shaft 20.

Advantageously, the ring 37 is made of an insulating material to avoid heat loss through the shaft 20 between the test chamber 9 and the unit for measuring 12.

The bore 33-1 of the housing 33 is essentially cylindrical. The outer ring 36-3 has a cylindrical outer surface 36-8 mounted in a clamped manner in the bore 33-1 of the housing 33. To provide a lower axial retention for the outer ring of the bearing 35, the bore 33-1 advantageously has a lower shoulder. To provide an upper axial support for the outer ring of the bearing 35 and a lower axial support for the outer ring 36-3 of the bearing 36, an intermediate spacer 46 is mounted axially between the bearings 35 and 36. To provide an upper axial support for the outer ring 36-3 of the bearing 36, a support ring 37 is fixedly mounted in the bore 33-1 of the housing 33.

The inner ring 36-2 has a cylindrical outer surface 36-6 with a concave annular groove 36-5 forming an inner bearing track, in which the balls 36-1 are accommodated. The outer ring 36-3 has a cylindrical bore 36-7 forming an outer bearing track, with which the balls 36-1 are in radial contact. Relative rotation between the inner ring 36-2 and the outer ring 36-3 about the central axis X33 is provided by bearing contact between the balls 36-1 and the inner and outer bearing tracks 36-5 and 36-7.

In the illustrated embodiment, the inner ring 36-2 is solid, i.e. obtained by machining or molding using a metal tube, bar, forged part, or laminated blank. The outer ring 36-3 may be formed by cutting from a metal tube and grinding to adjust the geometric tolerances.

Advantageously, the bearing 36 is provided with an annular cage 36-9 with a number of recesses in which the balls 36-1 are housed. Thus, to ensure uniform loading, the row of balls 36-1 is supported circumferentially, advantageously uniformly spaced apart.

Since, on the one hand, the support rod 17 is inclined with respect to the lower spring retainer 15 of the bump stop 2, and, on the other hand, the translatable second plate 4 applies an axial load to the bump stop 2, radial loads arise, in particular on the bump stop 2 and on the upper spring retainer 16. The radial load applied to the shaft 20 by the upper spring retainer 16 is transferred to the housing 33 fixed to the second plate 4 by means of bearings 35, 36. This arrangement constitutes a means of filtering of the radial loads, so that they do not affect the measurement of the friction torque in the measuring unit 12.

The measuring unit 12 also includes a measuring plate 39 arranged within the housing 33.

The measuring plate 39 has a lower surface connected to the second end 20-2 of the shaft 20 by means of an Oldham coupling 40, so that the shaft 20 transmits torque only to the measuring plate 39. Oldham couplings are known from the prior art, and the measuring plate 39 and the shaft 20 have a shape corresponding to the Oldham coupling 40. More specifically, the lower surface of the measuring plate 39 has a protrusion 39-1 extending in a first axial plane, the second end 20-2 of the shaft 20 has a protrusion 20-4 extending in a second axial plane perpendicular to the first axial plane, and the Oldham coupling 40 has a channel on its upper side for receiving the protrusion 39-1 of the measuring plate 39 and a channel on its lower side for receiving the protrusion 20-4 of the shaft 20. When the lower spring retainer 15 rotates with a rocking motion, the friction torque transmitted by the upper spring retainer 16 of the bump stop 2 is transmitted to the shaft 20 and then to the measurement plate 39 using the Oldham coupling 40.

Opposite its lower surface connected to the Oldham coupling 40, the measurement plate 39 has an upper surface which cooperates with the torque sensor 41. The upper surface of the measurement plate 39 has a protrusion 39-3 which is connected to the torque sensor 41 by a number of fixing screws.

The stop 42 with the ball is inserted axially between the measurement plate 39 and the shaft 20.

The stop 42 comprises an upper ring fixed to the underside of the measuring plate 39 by means of fixing screws. The stop 42 radially surrounds the Oldham coupling 40. The stop 42 comprises a lower ring fixed to the second end of the shaft 20, more specifically to a support ring 38 mounted on the second end of the shaft 20. A row of rolling elements, in this case balls, is inserted between the upper and lower rings, thus forming the stop 42, which rotate parallel to the radial plane and around the axis X33. The stop 42 allows the transmission of axial loads between the shaft 20 and the measuring plate 39.

Figure 6 shows the test bench 1, in particular the first mounting and operating configuration of the measuring unit 12.

The housing 33 has a free end located opposite the shaft 20 and closed by a cover 43, which is in contact with the torque sensor 41 and the upper edge of the housing 33. The housing 33 and the cover 43 are fixed to each other by a fixing screw 44 fixed in an opening formed through the upper edge of the housing 33 and the cover 43.

The second plate 4 can therefore apply an axial load to the bump stop 2 through the cover 43 fixed to the housing 33. The axial load is transmitted successively from the second plate 4 to the housing 33, to the cover 43, to the torque sensor 41, to the measuring plate 39, to the shaft 20 by means of the stop 42 with balls, and to the upper spring retainer 16 of the bump stop 2 by means of the second support 13. The bearings 35, 36 are freely mounted in the housing and thus do not interfere with the axial load.

Moreover, in contrast to the second mounting configuration of the unit for measuring 12 shown in FIG. 7 and described hereinafter, the measuring plate 39 and the housing 33 are separated from each other and the fixing screw 42 is removed. The measuring plate 39 is therefore free to deform under the action of the friction torque transmitted by the shaft 20 by means of the Oldham coupling 40.

The torque sensor 41 is therefore connected to the bump stop 2. The drive means 10 imparts a rotary-oscillating movement to the lower spring retainer 15 of the bump stop 2 by means of the first support 11. A friction torque is generated between the lower spring retainer 15 and the upper spring retainer 16. This friction torque is transmitted from the upper spring retainer 16 to the second support 13, in particular to the shaft 20, and then to the measuring plate 39 by means of an Oldham coupling. The torque sensor 41 therefore measures the friction torque by means of the measuring plate 39.

Advantageously, the torque sensor 41 may also be provided with a load measuring means.

Figure 7 shows the second mounting and operating configuration of the test bench 1, in particular the measuring unit 12.

The measurement plate 39 has a radial projection 39-2. The housing 33 has an opening 33-3 within which the radial projection 39-2 of the measurement plate 39 is received. The projection 39-2 rests axially on the radial edge 33-4 of the housing 33. The housing 33 and the measurement plate 39 are fixed to each other by a fixing screw 45, which is fixed in an opening formed through the projection 39-2 and the edge 33-4.

Advantageously, the measurement plate 39 may have a number of projections 39-2 and the housing 33 may have a corresponding number of openings 33-3 with radial edges 33-4 to accommodate these projections 39-2.

In the first mounting configuration of the measuring unit 12 shown in FIG. 6, the measuring plate 39 and the housing 33 are separated from each other.

In this second mounting configuration of the unit 12 for measuring, the measuring plate 39 is fixed to the housing 33 and thus to the second plate 4. The second plate 4 remains fixed during the test and is set to move in translation only during the phase of setting and adjusting the test conditions. The measuring plate 39 is therefore blocked in terms of operation in this second mounting configuration. The friction torque transmitted by the shaft 20 to the measuring plate 39 through the Oldham coupling 40 cannot be transmitted to the torque sensor 41.

Furthermore, in contrast to the first mounting configuration of the unit for measuring 12 shown in FIG. 6, the cover 43 and the housing 33 are separated from each other and the fixing screw 44 is removed.

The torque sensor 41 is not loaded by the measurement plate 39 and is not configured to perform measurements of the friction torque of the plate 39.

On the other hand, the second plate 4 can apply an axial load to the bump stop 2 through a measuring plate 39 fixed to the housing 33. The axial load is transmitted successively from the second plate 4 to the housing 33, to the measuring plate 39, through the ball stop 42 to the shaft 20, and then to the upper spring retainer 16 of the bump stop 2 by means of the second support 13.

On the other hand, the torque sensor 41 is decoupled from the bump stop 2. Known torque sensors available on the market are not suitable for long-term continuous operation. Due to this second mounting configuration, it is possible to carry out endurance tests of the bump stop 2 for long test times without using an additional test bench or removing the measuring unit 12. The coupling/decoupling of the measuring unit 12 is extremely simplified by simply mounting/removing the fixing screws 44, 45.

In a first configuration of the unit 12 for measuring the test bench 1, the shaft 20 is axially loaded. The inner ring of the bearing 36 is fixed in rotational and axial respect with the shaft 20 and is in a first axial position. In a second configuration of the unit 12 for measuring the test bench 1, the shaft 20 is not axially loaded. Between these two configurations, the shaft 20 is offset axially, this offset being of the order of tenths of a millimeter or of a millimeter. The inner ring of the bearing 36 is therefore located in a second axial position, axially offset with respect to its first position when the shaft 20 is under load. The balls 36-1 are accommodated in grooves forming the inner bearing tracks 36-5 of the inner ring 36-2 and therefore follow the axial displacements of the inner ring 36-2 between the first and second positions. The outer ring 36-3 is axially fixed in the housing and the balls 36-1 are axially repositioned by sliding on the cylindrical surfaces of the bores 36-7 of the outer ring 36-3. Thus, ball 36-1 provides rotational support for inner ring 36-2 and outer ring 36-3 of bearing 36 in both configurations of test bench 1.

Bearing 35 also has its own balls axially adjusted relative to its inner ring and its outer ring in a cylindrical outer bearing track, and is similar to bearing 36 described above.

The performance of bearings 35, 36 is therefore optimized, providing rotational support for shaft 20 without introducing additional frictional torque. Torque sensor 41 measures torque without being hindered by possible misalignment of bearings 36-2, 36-3.

The test bench 1 can serve both for the measurement of friction torque in the first mounting configuration shown in FIG. 6 and for endurance tests in the second mounting configuration shown in FIG. 7, carried out under application conditions related to rocking movements against any type of bump stop, tilted axial and radial loads, or even temperature.

In particular, it may be advantageous to provide a series of tests including a first measurement of the friction torque of the bump stop 2, then an endurance test, and a final measurement of the friction torque after the endurance test. Intermediate friction torque measurements may also be envisaged. All this is made possible by the test bench according to the invention, which has two possible configurations, the transition from one configuration to the other being possible to be carried out in a simplified manner.

The present invention, being a unit for measuring, is described without being limited to the example of a test bench for bump stop devices. Needless to say, the unit for measuring according to the present invention can be implemented in any friction torque measuring means of any rotating device under load, operating in such application conditions.

The present invention, a ball bearing, is described in the non-limiting example of application to a test bench for a bump stop device. The ball bearing according to the present invention may be used in any application with a rotating system.

LIST OF SYMBOLS 1 ...Test bench 2 ...Rotating device 3 ...First lower plate 4 ...Second plate 5 ...Tubular guide 6 ...Transmission mechanism 7 ...Third upper plate 9 ...Test chamber 10 ...Drive means 11 ...First lower support 12 ...Unit for measuring 13 ...Second upper support 14 ...Bearing 15 ...Lower spring retainer 16 ...Upper spring retainer 17 ...Support rod 18 ...First matching means 19 ...Fixing screw 20 ...Shaft 21 ...Second matching element 22 ...Pivot coupling 23 ...Guides 23-1, 23-2 ...Side rails 24 ...Coupling element 25 ...Pivot connection 26 ...Support plate 27 ...Motor 28 ...Drive plate 29 ...Connecting rod 30, 31 ...Swivel connection 32 Crank 33 Tubular housing 34 Fixing screw 35, 36 Bearings 37, 38 Support ring 39 Measuring plate 40 Oldham coupling 41 Torque sensor 42 Stop 43 Cover 44, 45 Fixing screw

Claims (8)

A unit (12) for measuring the friction torque of a rotating device (2) under load, comprising:
A torque sensor (41);
a shaft (20), the first end (20-1) of which is designed to be coupled to said rotating device (2);
a tubular housing (33) having a central bore (33-1) and fixed to a face of a plate (4), said shaft (20) extending through said plate (4) and into the bore (33-1) of said tubular housing (33);
At least one bearing (35, 36) comprising a first ring (36-2) provided with a first bearing track (36-5) and a second ring (36-3) provided with a second bearing track (36-7), said first ring (36-2) and said second ring (36-3) being concentric and rotating relative to each other about a central axis (X33), said bearing (35, 36) comprising a row of balls (36-1) mounted radially between said first bearing track (36-5) and said second bearing track (36-7), said bearing being fitted to said tubular housing for supporting said shaft (20) in a rotational movement. at least one bearing (35, 36) interposed between a bore (33-1) of a bearing (33) and the shaft (20), the first ring (36-2) being fixedly mounted on the shaft (20) and the second ring (36-3) being fixedly mounted within the tubular housing (33), the row of balls (36-1) being disposed between a first bearing track (36-5) on one of the first and second rings and consisting of a concave annular groove formed on a surface (36-6), and a second bearing track (36-7) on the other ring and consisting of a cylindrical surface;
a measurement plate (39) disposed within said tubular housing (33), said measurement plate (39) having a first surface connected to a second end (20-2) of said shaft (20) by means of an Oldham coupling (40), whereby said shaft (20) transmits torque only to said measurement plate (39), said measurement plate (39) and said shaft (20) having a shape corresponding to said Oldham coupling (40), said measurement plate (39) having a second surface cooperating with said torque sensor (41);
a stop (42) inserted between the second end (20-2) of the shaft (20) and a first surface of the measurement plate (39), the stop (42) comprising a first ring fixed to the first surface of the measurement plate (39), a second ring fixed to the second end (20-2) of the shaft (20) and at least one row of rolling elements inserted between the two rings, the row of rolling elements radially surrounding the Oldham coupling (40);
A unit for measuring. The measuring unit according to claim 1, further comprising a cage (36-9) for supporting the ball (36-1) in the circumferential direction. A unit for measuring as claimed in claim 1 or 2, wherein the first ring (36-2) is provided with a bore (36-4) and an outer cylindrical surface (36-6), the first bearing track (36-5) is a concave annular groove formed on the outer cylindrical surface (36-6), and the second ring (36-3) is provided with an outer surface (36-8) and a cylindrical inner bore (36-7), the second bearing track being formed by the cylindrical inner bore (36-7). A unit for measuring as claimed in claim 1 or 2, wherein the first ring is provided with a bore and an outer cylindrical surface, the first bearing track being formed by the outer cylindrical surface, and the second ring is provided with an outer surface and a cylindrical inner bore, the second bearing track being a recessed annular groove formed on the cylindrical inner bore. A unit for measuring according to any one of claims 1 to 4, wherein the tubular housing (33) has a free end located opposite the shaft (20) and closed by a cover (43), and a temporary connection means (44) between the cover (43) and the tubular housing (33), the cover (43) being in contact with the torque sensor (41). The measuring unit (12) according to any one of claims 1 to 5, comprising a temporary connection means (45) between the measuring plate (39) and the tubular housing (33), whereby the measuring plate (39) is fixed to the tubular housing (33), and the measuring plate (39) comprises at least one radial protrusion (39-2) capable of cooperating with the temporary connection means (45) and the tubular housing (33). A unit for measuring as claimed in claim 5 or 6, wherein the temporary connecting means comprises at least one screw (45) extending into corresponding holes in the measuring plate (39) and the tubular housing (33). A test bench (1) for measuring the friction torque of a rotating device (2), comprising:
A first fixing plate (3);
a second plate (4) that is translationally movable and can move toward or away from the first fixed plate (3) to apply an axial load to the rotating device (2);
a test chamber (9) formed between said plates (3, 4);
a driving means (10) fixed to the first fixed plate (3);
A measuring unit (12) according to any one of claims 1 to 7, which is fixed to the second plate (4),
a first support (11) rotatably connected to said drive means (10), the first support (11) being arranged in said test chamber (9) and designed to be fixed to a first element (15) of said rotating device (2) movable in rotation;
a second support (13) connected to the unit (12) for measuring, the second support (13) being designed to be fixed to a second element (16) of the rotating device (2);
A test bench (1) comprising: