WO2023218153A1

WO2023218153A1 - Method for mounting a rolling bearing on a bearing of an agricultural implement

Info

Publication number: WO2023218153A1
Application number: PCT/FR2023/050692
Authority: WO
Inventors: Laurent Pineda
Original assignee: Forges De Niaux
Priority date: 2022-05-13
Filing date: 2023-05-15
Publication date: 2023-11-16
Also published as: FR3135494A1

Abstract

The invention relates to a method for assembling a hub-rolling bearing assembly for rotatably mounting an agricultural disc onto a support arm (2), said assembly comprising: - a shaft (10) with a first shaft bearing zone (16) intended to receive a rolling bearing, - a double-row rolling bearing (20) comprising two inner rings (24, 26) mounted on the first bearing zone (16), an outer ring (28) and two sets of rolling elements (22), - a body (30) having a recess for receiving the double-row rolling bearing (20) and an outer radial collar (36) forming a flange, in which method a spacer (4) bearing against an inner ring (26) is mounted on the shaft by press-fitting, being prestressed towards the inner rings, the press-fitting ensuring that the spacer remains unmoving on a second bearing zone (17) as long as the axial forces exerted on the spacer (4) remain below a predetermined force.

Description

Title: ASSEMBLY OF A BEARING ON AN AGRICULTURAL TOOL BEARING

[0001] The present disclosure concerns mounting a bearing on an agricultural tool bearing.

Technical area

[0002] The present disclosure relates to the field of mechanical assemblies, and more particularly in the agricultural field, in which the external constraints exerted on the tools are significant.

Prior art

[0003] In the agricultural field, it is known to use for the preparation of a soil, in particular before planting or after a harvest, discs mounted on a frame to form a set of discs, parallel or not, this chassis being attached to an agricultural tractor, or similar. Several discs can be mounted integrally with a pivoting shaft relative to the chassis or the discs can be mounted pivoting individually relative to bearings. The term “disc” is used generically not only to designate tools with a flat shape and circular outline but also for tools having a concave or wavy shape and/or having a peripheral edge with a crenellated, wave-shaped shape. , etc..

[0004] The present disclosure concerns more particularly the case where the disks are each mounted pivoting relative to a bearing. Document EP3090612 for example shows a plowing disc mounted on an arm via an axis of rotation and a bearing. A hub is then bolted to the center of the plowing disc and receives a bearing and an axis of rotation: the hub is thus fixed on the disc and the axis on the arm carrying the disc, at least one bearing connecting the axis to the hub .

[0005] Document EP2689648 relates to a hub bearing assembly for rotatably mounting a plowing disc around an axis of rotation. This assembly is provided with: - an annular hub having an axially extending tubular part defining a cylindrical housing and an external flange for mounting a disc;

- a bearing unit mounted in the housing;

- an elastic damping body disposed in the housing and radially interposed between the hub and the outer ring of the bearing unit.

[0006] EP3292746 relates to a hub assembly for an agricultural implement which comprises a hub housing having an outer wall defining a mounting flange and an inner wall defining a through-cavity, an outer bearing race unit comprising one or more outer bearing rings press-fit into the through cavity, the outer bearing ring unit defining a reference axis of the hub assembly and having a first axial end bearing against a shoulder of the inner wall of the hub housing inside the through cavity. A semi-flexible open spacer ring is retained radially against the inner wall in the through-hole cavity. The semi-flexible open spacer ring has an inner axial end abutting a second axial end of the outer bearing ring unit opposite the first axial end and an outer axial end flush with or projecting from one face plane of the mounting flange.

[0007] In such an assembly, it is intended that the bearing unit comprises an outer ring and a pair of inner rings mounted side by side on a shaft. Two sets of rolling elements, balls, are interposed between the outer ring and the inner rings. The latter are blocked axially in a position resting against a shoulder on the shaft via a spacer installed on the shaft and constrained using a nut.

[0008] Usually, the nut which allows preloading on the spacer and which thus keeps the internal rings of the bearing unit locked is the nut allowing the mounting of the tool (plowing disc for example) on his arm. Therefore, during an after-sales service intervention, when the tool must be separated from its arm, care must be taken when reassembling to reproduce the pretension between the inner rings of the bearing unit. The tightening torque to be applied is very high (several hundred Nm). It is recommended to carry out this tightening using a torque wrench but this tool is not always available during reassembly.

[0009] As a result, it was found that when reassembling a tool on an arm, the required tightening torque was not always applied. Given the high stresses placed on an agricultural implement during use, it is essential to have sufficient tightening and ensure the prescribed preload between the inner rings of the bearing unit. Without this preload, the bearings can deteriorate quickly and must then be changed prematurely.

[0010] The present disclosure aims to provide a hub bearing assembly allowing assembly and disassembly of a tool arm while ensuring sufficient preload between the inner rings of the bearing unit after reassembly on the arm.

Summary

[0011] A method of assembling a hub and bearing assembly is proposed for the rotational mounting of an agricultural disc on a support arm, said assembly comprising:

- a shaft with a first shaft bearing zone intended to receive a bearing,

- a double row bearing comprising two inner rings on the first bearing zone, an outer ring and two sets of rolling elements each taking place between an inner ring and the outer ring,

- a body having, on the one hand, a housing for receiving the double row bearing and, on the other hand, an external radial flange forming a flange for receiving an agricultural disc, and

- a spacer resting on an inner ring.

[0012] The present disclosure proposes that: the spacer is mounted on a second shaft bearing zone by shrinking, in being pre-stressed towards the inner rings, the shrinkage guaranteeing that the spacer remains fixed on its bearing zone (which can be the extension of the first bearing zone receiving the bearing or be a distinct bearing zone with in particular a distinct diameter and preferably a distinct surface state) as long as the axial forces exerted on the spacer remain less than a predetermined force.

[0013] Shrinking ensures lifelong assembly of the spacer and the prestressing exerted during shrinking ensures prestressing on the inner rings of the bearing. In this way, by choosing the predetermined force according to the forces exerted on the spacer during use of the device, the bearing is mounted once and for all with the recommended constraints and the successive assembly and disassembly of the agricultural tool which will follow will not alter the quality of the bearing assembly. This predetermined effort advantageously corresponds to at least the maximum force transmitted by the agricultural disc in use. Here the spacer ensures once and for all the quality of the bearing assembly by exerting a predetermined preload while a mounting nut ensures the connection of the agricultural tool to an arm or similar. This mounting nut then no longer provides, as in the prior art, both a connecting function to an arm and a constraining function on the inner rings of the bearing (but only the connection to the arm).

[0014] The predetermined force is thus, for example, greater than 10,000 N (i.e. one ton), preferably greater than 50,000 N and even more preferably greater than 100,000 N.

The shrinking operation can be carried out for example by cooling the bearing zone of the shaft and/or by heating the spacer.

[0016] In this assembly method, the double row bearing can be held in its housing in the body by a circlip.

[0017] In an assembly method described above, it can also be provided that the shaft provided with its double row bearing and the spacer is introduced into the body, then mounted on a fixing arm, the latter being then sandwiched between the spacer and a nut mounted on a threaded end of the shaft. [0018] The present disclosure further comprises a hub and bearing assembly for rotatably mounting an agricultural disc on a support arm, said assembly comprising:

- a shaft with a first shaft bearing zone intended to receive a bearing,

- a double row bearing comprising two inner rings, an outer ring and two sets of rolling elements each taking place between an inner ring and the outer ring,

- a body having, on the one hand, a housing for receiving the double row bearing and, on the other hand, an external radial fixing flange for receiving an agricultural disc, and

- a spacer resting on an inner ring.

[0019] According to this present disclosure, the spacer is mounted on a second bearing zone and has a nominal inner diameter less than the nominal outer diameter of the second shaft bearing zone, and the spacer is mounted against an inner ring and hooped in such a way that the hooping guarantees that the spacer remains fixed in its bearing zone as long as the axial forces exerted on the spacer remain less than a predetermined force.

[0020] The characteristics set out in the following paragraphs can optionally be implemented. They can be implemented independently of each other or in combination with each other:

- the second shaft bearing zone (which may be an extension of the first shaft bearing zone or else be a distinct zone with for example a distinct diameter) has a nominal exterior diameter greater than at least 0.1 mm (1.0 10exp-4m) to the internal diameter of the spacer; and or

- the second shaft bearing zone has a surface condition different from that of the first bearing zone; and or

- the second shaft bearing zone has an arithmetic average roughness greater than 1 micron (1 10exp-6m), preferably greater than 3 microns, and/or - the second shaft bearing zone has a diameter smaller than the diameter of the first shaft bearing zone.

Brief description of the drawings

[0021] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the appended drawings, in which:

Fig. 1

[0022] [Fig. 1] shows in partial longitudinal section a hub and bearing assembly for rotatably mounting an agricultural disc on a support arm according to one embodiment.

Fig. 2

[0023] [Fig. 2] shows in perspective partially in section the whole of figure 1.

Description of embodiments

[0024] Reference is now made to Figures 1 and 2. These figures illustrate a hub and bearing assembly for rotating an agricultural disc on a support arm 2 illustrated very schematically in dotted lines. The agricultural disc (not shown) is intended to be able to rotate around an axis A.

The assembly illustrated in the drawing firstly comprises a shaft 10 with axis A. This shaft then carries a bearing 20 which finally takes place in a housing provided in a body 30 forming a hub.

The shaft 10 comprises a threaded end 12, a connection zone 14 intended to receive the support arm 2, a bearing having a first bearing zone 16 intended to receive the bearing 20 as well as a second bearing zone 17 intended to receive a spacer 4, and a head 18 arranged at the end of the shaft opposite the threaded end 12 so as to form a shoulder at the end of the first bearing zone 16.

The connection zone 14 has a diameter slightly greater than that of the threaded end. This connection zone 14 cooperates with the support arm 2 so as to allow the fixing of the shaft 10 on this support arm 2. It is planned in the illustrated embodiment to provide the connection zone 14 with at least one flat 15. Thus, if the support arm 2 is provided with a housing of complementary shape to that of the connection zone 14, the shaft 10 is blocked in rotation relative to the support arm 2 when the connection zone 14 is arranged in its housing in the support arm 2.

The second bearing zone 17 has for example the same diameter as the diameter of the connection zone 14. This second bearing zone 17 of the shaft 10 intended to receive the spacer 4 has for example an arithmetic average roughness greater than 1 micron (1 10exp-6m). It can be between 1.6 and 6.4 microns. This average roughness, usually denoted Ra, is for example 3.2 (that is to say 3.2 10exp-6).

The first bearing zone 16 is, as already mentioned, intended to receive the bearing 20. It has for example a diameter slightly larger than the second bearing zone 17 (of the order of a few tenths of a millimeter for example ). This first bearing zone 16 for the bearing 20 is machined in a conventional manner to receive a bearing. Its machining is carried out in such a way that its surface condition does not prevent (or promotes) sliding of a bearing ring mounted on this first bearing zone 16. We therefore have a first surface condition for the first bearing zone. bearing and a second surface state, preferably different from the first surface state, for the second bearing zone, each surface state being adapted: a first surface state intended for a bearing assembly and allowing movement of the inner rings of bearing and a second surface condition favoring hooking of the spacer on the shaft. The first bearing zone 16 has, for example, as illustrated in the drawing, an axial length very slightly less than the axial length of the bearing 20.

The shaft 10 has at its end opposite the threaded part a head 18 of diameter substantially greater than the diameter of the first bearing zone 16 so as to form at the end of this zone opposite the threaded end 12 a shoulder intended to serve as a stop for the bearing 20 as explained below. The bearing 20 is a double bearing, that is to say which comprises a double row of rolling elements. In the present case, as illustrated in the drawing, the bearing 20 has two rows of balls 22. Each row of balls 22 corresponds to an inner ring. We thus have a first inner ring 24, a second inner ring 26. The bearing 20 finally includes a single outer ring 28. The inner rings are each a separate part of the shaft 10 just as the outer ring 28 is a separate part of the body 30.

The first inner ring 24 and the second inner ring 26 each have an inner diameter corresponding to the outer diameter of the bearing zone 17. The machining tolerances are usual for mounting a bearing. The bearing must be mounted tight while still being able to slide axially on its bearing area.

[0033] Purely by way of illustration, taking into account the field of application, the diameter of the shaft 10 at each of the bearing zones is for example between 20 and 100 mm.

The body 30 has the function of connecting the shaft, via the bearing 20, to the agricultural disc. For this purpose it then mainly comprises a housing for receiving the bearing 20 and a fixing flange 36.

The housing of the bearing 20 is produced by a tubular part 32 extending axially around the shaft 10 and the bearing 20. The internal diameter of the tubular part 32 is adapted to the external diameter of the outer ring 28 of the bearing 20. Conventionally for mounting a bearing, we will choose here an adjustment with clearance for the mounting of the outer ring 28 relative to the tubular part 32.

The tubular part 32 has at a first end a rim 34 extending radially inwards and intended to form a stop for the outer ring 28 of the bearing 20. At its other end, the tubular part 32 includes the flange fixing 36 for agricultural disc which is in the form of a collar extending radially outwards and has tapped holes 38 to allow the fixing of an agricultural disc. The face of the collar intended to be opposite the agricultural disc is for example provided with a annular groove for housing an O-ring 40. We also note the presence inside the tubular part 32 of a peripheral groove intended to receive a circlip 42. The latter when mounted in the peripheral groove also forms a stop for the outer ring 28 of the bearing 20.

[0037] Finally, as illustrated in the drawing, the assembly described here also includes the spacer 4 in the form of a socket. The latter has an interior diameter to cooperate with the second bearing zone 17 and an exterior diameter less than the interior diameter of the rim 34.

[0038] For mounting the spacer 4 on the second bearing zone 17, provision is made for the external diameter of the shaft at its second bearing zone 17 to be, for example, larger than the internal diameter of the spacer 4 with a value between 0.05 and 0.5 mm, preferably between 0.10 and 0.20 mm. This difference in diameter takes into account, on the one hand, the nominal dimension of the bearing zone 16 of the shaft 10 and the nominal dimension of the internal diameter of the spacer and, on the other hand, the manufacturing tolerances of the shaft and inner bearing rings.

[0039] For purely illustrative and non-limiting purposes, we could for example have a shaft with a diameter of 28.0 k8 (in mm) at the level of the second bearing zone 17 and a spacer 4 having an internal diameter of 27.9 k7 (in mm). We then have a difference in diameter of between 0.10 mm and 0.154 mm. To be able to mount the spacer 4 on the second bearing zone 17, it is proposed to carry out assembly by shrink fit as will be explained later. For this shrink fit, we will use parts (shaft and bearing, i.e. interior face of the spacer) with diameter differences going beyond the assembly tolerances defined for example in the ISO 286-2 standard if although the nominal dimension of the shaft is preferably greater than the nominal dimension of the internal diameter of the spacer as illustrated by the previous numerical example.

[0040] The assembly of the assembly described above and illustrated in the drawing can for example be carried out as proposed below.

The bearing 20 is first mounted with clamping on the first bearing zone 16 of the shaft 10. For this purpose, the bearing 20 is for example mounted on shaft 10 to the press. The bearing 20 is then mounted on the shaft 10 such that the first inner ring 24 abuts on the head 18 of the shaft 10.

[0042] Once the bearing 20 is in place, the spacer 4 is put in place. Taking into account the differences in diameter between the interior of the spacer 4 and the exterior of the first bearing zone 16, heating of the spacer 4 is carried out for example. This heating can be carried out in an oil bath or by induction.

At the same time, the shaft 10 is cooled, for example by immersing the shaft 10 in a bath of liquid nitrogen.

[0044] The subsequent mounting of the spacer 4 on the shaft (on its second bearing zone 17) is for example carried out hydraulically (but can also be carried out by mechanical screw tightening using a preload nut removed after fretting). It is important here during assembly to exert a predetermined constraint (depending on the characteristics in particular of the bearing) on the first inner ring 24 and the second inner ring 26 of the bearing against the head 18 and to maintain this constraint until the The shaft 10 and the spacer 4 are substantially at the same temperature.

[0045] Hard hooping is thus carried out. When the second bearing zone 17 heats up and the spacer 4 cools, very strong radial stresses appear between the two parts. The tightening achieved is almost final. Taking into account the constraints, an intimate connection is made and a very high resistance to sliding exists between the spacer 4 and its shaft, in particular its second bearing zone 17. This resistance to sliding is such that an axial force of several tonnes, or even several tens of tons (1 ton corresponds approximately to 10,000 N) would be necessary to start moving the spacer axially relative to the shaft 10.

[0046] The hooping is carried out taking into account the maximum axial forces that can be exerted when using the corresponding agricultural disc. During this use, the spacer 4 must not risk sliding on the shaft 10. It thus guarantees the maintenance of the good prestress produced during the assembly on the shaft 10 of the bearing and the spacer on both rows of bearing 20. This preload becomes independent of the tightening of a nut screwed onto the end threaded 12 to fix the agricultural disc on a support arm 2. Thus, the disc can be mounted and disassembled without influencing the preload exerted on the two inner rings of the bearing 20. So that the disc (or other tool) is mounted on its arm support or not, the preload on the inner rings of the bearing is ensured. The shrink spacer provides the pre-tensioning, a mounting nut (not shown) intended to take place on the threaded end 12 ensures the connection with a support arm).

[0047] The state of roughness of the second bearing zone 17 contributes to the quality of the connection between the spacer 4 and the shaft 10. The axial prestress exerted on the bearing 20, in particular its inner rings, maintained while the Room temperatures return to approximately room temperature and are then maintained for life.

The assembly formed by the shaft 10, the bearing 20 and the spacer 4 is then introduced into the body 30, the threaded end 12 of the shaft being introduced first into the body 30 on the side of the fixing flange 36 to emerge from the side of the rim 34. The outer ring 28 then abuts against the rim 34. The circlip 42 can be positioned to block the bearing 20, more precisely its outer ring 28, in the housing provided for receive the bearing 20 in the body 30.

[0049] This assembly is then ready, on the one hand, to be mounted on a support arm 2 and, on the other hand, to receive an agricultural disc.

[0050] For mounting on the support arm 2, the connection zone 14 is simply positioned with the flat 15 in the housing provided for this purpose on the support arm 2 and said support arm 2 is then sandwiched between the spacer 4 and a nut (not illustrated) cooperating with the threaded end 12.

[0051] For mounting the agricultural disc, it is positioned against the fixing flange 36, preferably with the interposition of the O-ring 40, and is screwed onto this flange (or collar).

[0052] For the implementation of this process, the dimensioning of the shaft and the spacer depends in particular on the materials chosen to make these parts and also their dimensions. The parts should be dimensioned in such a way that the deformations suffered during shrinking remain in the elastic range. Any plastic deformation of the parts should be avoided.

[0053] The hooping is carried out in such a way that the spacer does not slide on the shaft, particularly when using the agricultural disc. The axial forces exerted on the spacer during use of the agricultural disc can be estimated and are also estimated in the prior art to determine in particular the tightening stress of the fixing nut.

[0054] The hooping presented is a straight hooping (cylindrical surfaces) but it is also possible to have a conical hooping, or even an inverted conical hooping.

[0055] Shrinking as proposed here is not usual in mechanics. The differences in dimensions of the shaft and the bore (spacer) go beyond the standardized adjustments and it is therefore necessary to act on the nominal dimension of the parts.

Industrial application

[0056] This technical solution can be applied in particular in the agricultural field in which the constraints exerted are very significant. A significant torque is exerted on agricultural discs and they also undergo significant shocks (in particular impacts with stones).

[0057] In the state of the art prior to this disclosure, the tightening of the inner rings of the bearing is carried out by the final tightening of the mounting nut on the threaded end of the shaft. For proper operation of the bearing, a tightening torque of the order of 100 Nm to several hundred Nm must be exerted on this mounting nut so that it ensures both the connection with the support arm and also the tightening of the bearing rings. This torque is applied according to the manufacturer's specifications during first assembly. On the other hand, when an agricultural disc must be dismantled to be replaced or for another intervention, it happens that this intervention is not carried out in the workshop and the tightening torque exerted on the nut during reassembly is approximate. This can lead to serious damage to the bearing which must then be changed. [0058] The solution proposed here makes it possible to guarantee mounting of the bearing on its shaft with the correct stress for the entire life of the bearing.

[0059] Thus the reliability of the assembly is significantly increased without generating significant additional costs during its manufacture. [0060] The present disclosure is not limited to the exemplary embodiment and its variants described above, only for illustrative purposes, but it encompasses all the variants that those skilled in the art may consider in the context of the protection sought.

Claims

[Claim 1] Method for assembling a hub and bearing assembly for rotating an agricultural disc on a support arm (2), said assembly comprising:

- a shaft (10) with a first shaft bearing zone (16) intended to receive a bearing,

- a double row bearing (20) comprising two inner rings (24, 26) mounted on the first bearing zone (16), an outer ring (28) and two sets of rolling elements (22) each taking place between a ring inner ring (24, 26) and the outer ring (28),

- a body (30) having, on the one hand, a housing for receiving the double row bearing (20) and, on the other hand, an external radial flange forming a fixing flange (36) for receiving an agricultural disc, and

- a spacer (4) resting on an inner ring (26), characterized in that the spacer (4) is mounted on a second shaft bearing zone (17) by shrink fit, being pre-stressed towards the inner rings , the shrink-fit guarantees that the spacer remains fixed on its bearing zone (17) as long as the axial forces exerted on the spacer (4) remain less than a predetermined force.

[Claim 2] Assembly method according to claim 1, characterized in that the surface state of the first bearing zone (16) is different from the surface state of the second bearing zone (17).

[Claim 3] Assembly method according to one of claims 1 or 2, characterized in that the predetermined force is greater than 10,000 N, preferably greater than 50,000 N and even more preferably greater than 100,000 N.

[Claim 4] Assembly method according to one of claims 1 to 3, characterized in that the shrinking operation is carried out by cooling the second shaft bearing zone (17) and heating the spacer (4 ).

[Claim 5] Assembly method according to one of claims 1 to 4, characterized in that the double row bearing (20) is held in its housing in the body (30) by a circlip (42).

[Claim 6] Hub and bearing assembly for rotatably mounting an agricultural disc on a support arm (2), said assembly comprising:

- a double row bearing (20) comprising two inner rings (24, 26), an outer ring (28) and two sets of rolling elements (22) each taking place between an inner ring (24, 26) and the outer ring (28),

- a body (30) having, on the one hand, a housing for receiving the double row bearing (20) and, on the other hand, an external radial fixing flange (36) for receiving an agricultural disc, and

- a spacer (4) resting on an inner ring (26), characterized in that the spacer (4) is mounted on a second bearing zone (17) and has a nominal interior diameter less than the nominal exterior diameter of the second shaft bearing zone (17), and in that the spacer (4) is mounted against an inner ring (26) and shrink-fitted in such a way that the shrink-fit guarantees that the spacer remains fixed on its bearing zone (16) as long as the axial forces exerted on the spacer (4) remain less than a predetermined force by exerting a prestress on the internal rings (24, 26) of the bearing.

[Claim 7] Hub and bearing assembly according to claim 6, characterized in that the second shaft bearing zone (17) has a nominal outer diameter greater than at least 0.1 mm (1.0 10exp-4m) to the inside diameter of the spacer (4).

[Claim 8] Hub and bearing assembly according to one of claims 6 or 7, characterized in that the second bearing zone (17) has a surface condition different from that of the first bearing zone (16). [Claim 9] Hub and bearing assembly according to one of claims 6 to 8, characterized in that the second shaft bearing zone (17) has an arithmetic average roughness greater than 1 micron (1 10exp-6m), of preferably greater than 3 microns. [Claim 10] Hub and bearing assembly according to one of claims 6 to 9, characterized in that the second shaft bearing zone (17) has a diameter less than the diameter of the first bearing zone (16) of TREE.