FR2967201A1 - System for producing dynamic seal of hydrostatic motor to be mounted on wheel shaft of vehicle, has centering ring mounting dynamic lip seal floating on support plane with respect to shaft before its attachment to support plane - Google Patents

Abstract

The present invention relates to a system for producing a dynamic seal of a hydrostatic motor (M) intended to be mounted on a shaft (1), said system being characterized in that it comprises: - a sealing element comprising a support (3) and a dynamic sealing means (4), said support (3) being provided with a centering surface (37) with respect to a shaft (1), - centering means (7) said sealing member with respect to said shaft (1), - fixing means (6) of said support (3) on a plane support in a position defined by said centering means (7), said centering means (7) being adapted to mount said floating sealing element on said flat support relative to the shaft (1) before it is attached to said flat support.

Description

GENERAL TECHNICAL FIELD

The present invention relates to the field of hydrostatic engines intended to be mounted on a shaft, and more specifically the achievement of dynamic sealing in such engines.

STATE OF THE ART

For a hydraulic motor mounted on a shaft, in particular in the case of a fixed shaft on which is mounted a motor with rotating housing driving a wheel, it is necessary to have a motor seal on the side of the shaft; for example an oil / air type seal in the case of a hydrostatic transmission engine bearing, or oil / grease type in the case of a hydrostatic transmission engine added in the form of a hydrobase on a shaft already bearing the wheel bearing. The seal to achieve this seal must have a good seal during the expected mileage of the hub (friction, wear), do not leak to the crankcase pressure, support crankcase pressure peaks for the system using crankcase pressure to maneuver hydraulic devices, for example the operations of interconnection or decrabotage engines.

In order to achieve a satisfactory seal, the seal must be centered with respect to the rotating part on this seal. Centering is defined by a very low tolerance; for example concentricity of 0.1 mm, which means that the maximum centering defect of one part relative to another, must be 0.05mm. Such a tolerance is very complex to achieve in turning by conventional means, especially in devices made by stacking several parts, in which the machining dispersions accumulate, which prevents such low tolerances. Indeed, the known solutions which have such a tolerancing are solutions in which the centering is made between two one-piece parts, the respective surfaces of which are formed in a single turning operation, that is to say in machining on a turn, without removing the part of the turn between the machining of the different surfaces. However, such solutions are not suitable for applications with high operating constraints, for which a stack of several parts is necessary, which therefore induces the previously mentioned problems concerning tolerances.

Figure 1 shows an example of a solution according to the state of the art. Figure 2 shows a detailed view of a portion of Figure 1, while Figure 3 shows a variant of Figure 2. This figure has a shaft 1 on which is mounted a hydraulic motor M. The shaft 1 is provided of bearings 12, here a roller bearing, arranged in a bearing housing 13. A flange 15 is fixed on the housing 13, this flange for fixing a wheel. (Other variants further comprise a brake disk disposed between the rolling bearing housing 13 and the flange 15.

A seal is necessary between the hydraulic motor M and the shaft 1, in order to maintain and to avoid degrading the oil ensuring the lubrication of the motor M; this seal being for example of the oil / air type in the case of a hydrostatic transmission engine bearing, or oil / grease type in the case of a hydrostatic transmission motor added to a shaft already bearing the bearing. However, commonly used shafts, for example to achieve the vehicle wheel shafts do not have a high hardness, and therefore can not withstand the permanent friction of a dynamic sealing element mounted directly on the shaft. Also sometimes, the material or the method of machining or finishing these trees does not provide a friction track of sufficient quality to ensure a sufficient life of a dynamic seal on its friction surface, and more precisely with regard to the quality of the surface condition: roughness, geometrical defects, etc. Thus, a friction track 2, commonly known as a hoop 2, that is to say a part made of a material having a hardness, a geometry (in the direction of circularity, straightness) and a surface state sufficient to achieve a good frictional range. The hoop 2 is then mounted tight on the shaft 1, the seal being provided by a static seal 21, typically an O-ring. A seal ring 3 is mounted around this band 2, the seal ring 3 serving to support a lip seal 4 sealing between the ferrule 2 and the seal ring seal 3. Thus, during the relative rotation of the motor M relative to the shaft 1 (or vice versa), the seal ring 3 rotates around the hoop 2 and the shaft 1, and the lip seal is not directly in contact with the shaft 1, but the fret 2.

Alternatively as shown in Figure 3, it is the hoop 2 which serves to support the lip seal 4, the latter then being fixedly mounted relative to the hoop 2 while the seal ring 3 is rotatably mounted, rubbing in contact with the lip seal 4. The operation is similar to the variant shown in Figure 2, with the exception of the lip seal 4 whose contact surfaces with the hoop 2 and the seal ring 3 are reversed.

The embodiment shown further comprises a reinforced seal 5, formed of a shoe 51 and an O-ring 52, stacked on the hoop 2 and arranged in a housing of the seal ring seal 3. This reinforced seal 5 is arranged so as to prevent the lip seal 4 from being directly exposed to a peak pressure in the motor M; it is therefore arranged between the motor M and the lip seal 4.

The shoe 51 is made of friction material, and is held in contact with the hoop 2 by the O-ring 52, which for its part performs a seal without friction with the seal ring seal 3. Such a reinforced seal 5 is well known to the person skilled in the art, and has been marketed on engines of the Poclain Hydraulics brand for many years; we can for example cite the engines sold under the name G4 since 1982 which proposed such a reinforced reinforced optional, or engines of the MS range whose name includes the letter E, for example the engine designated by the commercial code MS18-0 -121-F12-1120-E00 marketed since March 1998.

In such an arrangement, the seal ring 3 is tightly mounted on the wheel flange 15. Thus, the manufacturing tolerances of the various stacked parts add up, which prevents a very low tolerance, which has an impact on the correct positioning of the sealing element and thus on the tightness achieved, and consequently on the service life of the components. More precisely, in the example shown in FIG. 1, by producing a rib chain from the seal ring 3, the respective tolerances of the hoop 2, the shaft 1, the bearing 12, the bearing housing 13 and wheel flange 15, in addition to the tolerances of the seal ring 3 itself. The tolerance of the assembly being equal to the sum of the tolerances of the various components, it is then impossible to obtain a low tolerance for the centering of the sealing element on the shaft 1 without requiring prohibitive machining constraints. , especially as some of the parts such as the wheel flange 15 are massive parts, for which it is all the more difficult to obtain low tolerances values.

PRESENTATION OF THE INVENTION The present invention aims to remedy this problem, by proposing a device for obtaining a seal with a very low positioning tolerancing, typically of the order of 0.05mm.

For this purpose, the invention proposes a system for producing a dynamic seal of a hydrostatic motor intended to be mounted on a shaft, said system being characterized in that it comprises: a sealing element comprising a support and dynamic sealing means, said support being provided with a centering surface with respect to a shaft, means for centering said sealing element with respect to said shaft, means for fixing said support (3) on a plane support in a position defined by said centering means (7), said centering means (7) being adapted to mount said floating sealing element on said plane support with respect to the shaft (1) before being fixed on said flat support.

As a variant, said system comprises one or more of the following characteristics, taken independently or in combination: said centering means are adapted to allow a centering of said sealing element with a tolerance of 0.05 mm with respect to said shaft; said sealing element comprises a seal ring forming said support, a lip seal forming said dynamic sealing means, said lip seal being positioned in said seal ring via a holding surface of said seal ring. a centering surface, said surface being positioned with a tolerance of the order of 0.02 mm with respect to the holding surface; - A friction track adapted to be mounted on the shaft, said sealing member being mounted around the friction track, so that the dynamic sealing means is frictionally mounted on said friction track; - Said centering means comprise a ring adapted to be disposed in contact with said support on the one hand, and on the other hand in contact with the shaft or the friction track; said support furthermore comprises a housing in which a static sealing gasket mounted tightly on a friction pad is arranged, said friction pad being adapted to be tightly mounted on the shaft, respectively the friction track, so as to isolating said dynamic sealing means from said hydrostatic motor. In a variant, said support arranges an internal space between said dynamic sealing means and said housing, said internal space being connected to a pressure discharge duct. - Said centering means protrude from said sealing member and have a gripping area adapted to allow their removal after fixing said sealing member. Alternatively, said gripping zone is adapted to prevent mounting of a hydrostatic motor.

The invention also relates to an assembly for producing a dynamic seal of a motor intended to be mounted on a shaft, comprising: - a friction track, - a sealing element mounted around said friction track, comprising a support and dynamic sealing means, said support being provided with a centering surface, - centering means, - means for fixing said support in a defined position, said centering means being arranged in contact with the track of friction on the one hand, and support on the other.

Alternatively, said centering means are mounted tight relative to said friction track and said support, so as to form an assembly adapted to be integrally mounted on a shaft.

The invention furthermore relates to a method for producing a dynamic seal of a hydrostatic motor mounted on a shaft, comprising the steps of: positioning a sealing element around said shaft against a plane support, said element sealing device comprising a support associated with a dynamic sealing means, and being associated with centering means allowing a floating mounting of said sealing element against said flat support, - adjusting the positioning of said sealing element with respect to said shaft - Fixing said sealing element via fastening means in a position defined by said centering means.

Alternatively, said method further comprises a step of disposing a friction track on the shaft, said sealing member being mounted around said friction track.

PRESENTATION OF FIGURES

Other features, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and nonlimiting, and which should be read with reference to the appended drawings, in which: FIGS. 1, 2 and 3 already presented illustrate several embodiments of dynamic sealing according to the state of the art; FIGS. 4 and 5 show an example of positioning a dynamic seal on a shaft according to one aspect of the invention; FIGS. 6 and 7 show variants of the embodiment shown in FIG. 5; FIG. 8 shows an assembly according to one aspect of the invention for effecting dynamic sealing of a hydraulic motor, FIG. 9 illustrates an overall view of a hydraulic motor variant mounted on a shaft according to an aspect of the invention. invention. In all the figures, identical or similar elements are identified by the same reference numerals.

DETAILED DESCRIPTION FIGS. 4 and 5 show an example of positioning a dynamic seal on a shaft according to one aspect of the invention. In the embodiment shown; the shaft 1 is equipped with a hoop 2 mounted tightly on the shaft 1, and whose sealing is achieved by means of a static seal 21, here an O-ring disposed in a housing arranged in the tree 1.

The seal ring 3 is provided with the dynamic seal 4, here a lip seal which is disposed against a bearing surface 34 of the seal ring 20 seal 3, and is adapted to be mounted friction on the hoop 2, or directly on the shaft 1 in the embodiments in which the hoop 2 is not necessary. The assembly thus formed by the seal ring 3 and the lip seal 4 form a sealing element, composed of a support: the seal ring 3 and a sealing element: the lip seal 4 The seal ring 3 comprises attachment zones 36 adapted to cooperate with fastening means 6, here screws for locking the position of the seal ring 3 when pressed against a flat bearing surface, typically a surface flat support of the housing. These attachment zones 36 allow displacement of the seal ring 3 on the plane support of sufficient amplitude to allow the centering of the sealing element relative to the shaft 1 before attachment to said support plane. This amplitude is advantageously greater than or equal to the sum of the machining defects of the different parts and / or of the adjustment clearance between the different parts, for example of the order of 1 mm.

Figure 4 shows the elements in exploded view; the hoop 2, the seal ring 3 and the fastening means 6 are shown during assembly on the shaft. FIG. 5 shows the elements assembled on the shaft 1, and associated with centering means 7.

These centering means 7 are adapted to, in cooperation with a centering surface 37 of the seal ring 3, machined with a very small tolerance relative to the bearing surface 34, for example a tolerance of the order of 0 , 02mm, allow to place in position the seal ring 3 with respect to the shaft 1 or, where appropriate, the hoop 1 5 2, in order to perform the centering. The centering means 7 may for example be made of a plastic material such as acetal resin. The seal ring 3, as well as the shaft 1 or, if appropriate, the hoop 2 are specially designed to cooperate with said centering means 7, and therefore have suitable contact surfaces such as the centering surface 37 of the ring 3, or in the case of the hoop 2, dimensions so that its length allows it to extend beyond the contact with the seal ring 3 to provide a contact surface to the centering means 7. In the embodiment shown in FIG. 5, the centering means 7 are a centering ring adapted to cooperate with the centering surface 37 of the seal ring 3 in order to ensure its positioning relative to the shaft. 1, in this case ensuring contact between the seal ring 3, the centering ring 7 and the hoop 2. The centering ring 7 here has an L-shaped, one branch is supported on the one hand against the centering surface 37 of the bushing e seal 3, and secondly against the outer diameter of the hoop 2.

In the embodiments in which the sealing element formed of the seal ring 3 and the lip seal 4 is directly in contact with the shaft 1, without the interposition of a hoop 2, then the centering ring 7 is in contact on the one hand with the centering surface 37 of the seal ring 3, and on the other hand with the outer diameter of the shaft 1.

Thus, the positioning and therefore the concentricity between the seal ring 3 and the shaft 1 is achieved by means of a reduced number of elements, namely the seal ring 3 itself, the shaft 1, the means centering 7 and if necessary the hoop 2. The number of elements is therefore considerably reduced compared to the assemblies of the state of the art, which makes it possible to obtain a tolerancing of the increased assembly. In addition, the considered elements such as the ring 1 5 seal door 3, the centering means 7 and if necessary the hoop 2 are precision parts, can be machined with a very low tolerance, which can reduce d all the more the tolerancing of the whole. The use of a specific surface 37 of the seal ring 3 in order to achieve the positioning of the centering ring makes it possible to machine it with a very low tolerance, for example of the order of 0.02 mm to the diameter relative to to the bearing surface 34, these two surfaces 34 and 37 being made during a single turning operation. The centering accuracy of the seal ring therefore depends only on a small number of contact surfaces (two contacts only), and a mounting clearance which can be very small. This clearance can also be zero in the case of a centering means machined to perform a certain tightening on the surfaces 34 and 37.

The centering ring 7 advantageously has a free end forming a gripping zone that can be grasped by a user, in order to remove it once the centering of the sealing element is made around the shaft 1, and after its fixing. by the clamping means 6.

Alternatively, said gripping zone is adapted to prevent the introduction of a hydrostatic motor attached to said sealing element until said centering means 7 has not been removed.

This embodiment also has a reinforced seal 5, formed of a shoe 51 and an O-ring 52, stacked on the hoop 2 and arranged in a housing of the seal ring 3. This reinforced seal 5 is disposed of in order to prevent the lip seal 4 from being directly exposed to a peak pressure in the motor M; it is therefore arranged between the motor M and the lip seal 4. The shoe 51 is made of friction material, and is held in contact with the band 2 by the O-ring 52, which for its part performs a seal without friction with the seal ring 3.

According to a particular variant, the seal ring defines an internal space between the lip seal 4 and the housing of the seal ring 3 comprising the reinforced seal, that is to say between said dynamic sealing means and the reinforced sealing 5, said inner space being advantageously provided with a pressure relief bore. This pressure relief piercing advantageously makes it possible to evacuate an excess of pressure in said internal space, typically towards a reservoir at ambient pressure or towards the outside.

FIG. 6 shows a detailed view of a variant of the embodiment shown in FIG. 5, in which the centering ring 7 is L-shaped and is contiguous to the seal ring 3. In this embodiment, the centering ring 7 is arranged so as to be integrated, and does not have a protruding part of the seal ring 3.

FIG. 7 shows another variant according to the invention, in which the centering means 7 comprise a PTFE bushing or ring, any other material adapted to friction or any material which, once a given number of rotations have been carried out. , wears without consequence for the proper functioning of the seal and the motor, typically intended to remain in place once the sealing element fixed on the shaft 1, until the replacement of the sealing member or more precisely the lip seal 4.

FIG. 8 shows an assembly comprising - a ferrule 2, - a seal ring 3, a lip seal 4 mounted to bear against a bearing surface 34 of the seal ring 3, and providing a dynamic seal around the ferrule 2, - reinforced sealing means, comprising a shoe 51 and an O-ring 52, stacked on the ferrule 2 and arranged in a housing of the seal ring 3, - fixing means 6, typically screw, - centering means 7 of the seal ring seal relative to the hoop 2, namely a centering ring 7 in the example shown.

The seal ring 3 is held around the band 2 by the lip seal 4, as well as by the centering means 7 if the latter are mounted tight around the band 2 and in or around the seal ring 3 For this purpose, the centering means 7 may comprise clamping or holding means on the parts opposite not shown; The user can mount it directly on a shaft 1, and fix it via the fixing means 6. Such an assembly can thus be provided directly to a user for mounting on a shaft 1, to reduce the necessary operations and obtain an assembly with very low tolerancing 30 thanks to the assembly carried out by the centering means 7. More precisely, the assembly is positioned in abutment on a flat surface before being centered with respect to the shaft 1, before fixing on said flat surface with the fixing means 6. A floating assembly of the assembly is thus defined on the flat surface, typically a planar housing surface, that is to say an assembly allowing two degrees of freedom in translation and a single degree of freedom in rotation. Thus, by ensuring a sufficient functional clearance to this floating assembly, that is to say a functional clearance greater than or equal to the eccentricity defect of the various parts connecting said planar surface to the shaft 1, a user is allowed to to obtain a precise centering before fixing, by overcoming machining and stacking errors, contrary to the state of the art which mounted the sealing assembly directly tight in a housing part, and thus inducing a probable error of important positioning. In the case where the centering element 7 is mounted tight, that is to say with a zero clearance on the hoop 2 and the seal ring 3, this floating assembly has a positioning error which depends only on the 1 5 machining errors or tolerances of the shaft 1 and the hoop 2.

FIG. 9 shows an exemplary view of a hydraulic motor M mounted on a shaft 1 by means of a system according to the invention. Compared to the example shown in FIG. 1, the presence of a brake disc 14, mounted between the rolling bearing housing 13 and the wheel flange 15, is observed, this brake disc 14 being able to be removed in certain modes. of realization. The seal ring 3 is here fixed to the wheel flange 15 via fixing means 6, namely screws which immobilize it with respect to a flat surface of the wheel flange 15. This figure also illustrates two variants of the wheel flange 15. in which the internal space between the dynamic seal 3 and the reinforced seal 5 is connected to a pressure relief duct. These two variants are shown on either side of the axis of rotation indicated in FIG. 9. According to a first variant, said pressure-relief duct is made by arranging a hole 25 in the hoop 2 associated with a hole. 16 in the shaft 1, which typically opens on a tank at atmospheric pressure or outwardly. This bore 16 of the shaft 1 is typically associated with a groove 17 of greater width than the bore 16, to facilitate alignment with the drilling of the hoop 2. According to a second variant also shown in this figure, it is realized the pressure discharge conduit via a bore 18 formed in the seal ring 3, connected to a conduit 19 formed in the flange 15, connected to the outside via a protective valve 22 adapted to prevent external projections from entering via the conduit 19; for example a valve calibrated at a pressure of 0.2 bar.

Considering the various embodiments described above, the following mounting methods can be defined. A first mounting method is described below. In a first step, a sealing element is formed by combining a seal ring 3 with a lip seal 4, and optionally with a reinforced seal 5 typically comprising an O-ring 52 and a pad 51. Alternatively, the lip seal 4 is fitted on a shaft 1 or a hoop 2, and the seal ring 3 is added thereafter, then forming the sealing element. The centering means 7, typically a ring are mounted on the seal ring 3, and on the hoop 2 if it exists. This allows a clearance-free assembly between the collar 2 and the centering means 7 and / or between the seal ring 3 and the centering means 7. If the centering means is mounted with clamping, for example at the press, he stands himself in the seal ring. He also participates in maintaining the fret if it exists.

Next, said assembled sealing element is positioned with the centering means around a shaft 1, or, where appropriate, around a band 2, in contact with a flat surface such as a casing or a brake flange if we refer to the example shown in Figures 1 and 9. In the case of mounting with a fret, this positioning is done by pressing the end of the fret 2. The set fret / element sealing 4 and 5 / centering means 7 is positioned in a single operation by driving the hoop 2. The assembly is advantageously made tight, for example by means of a press which allows a mounting without play between the fret 2 and the tree 1.

The positioning of the sealing element is automatically achieved thanks to the centering means 7 which make it possible, by virtue of the floating assembly as defined previously of said sealing element on the flat surface, to position the sealing means with respect to the shaft 1 or if necessary on the hoop 2, which thus allows to adjust the positioning before fixing. Then fixing said sealing member via fastening means in a position defined by said centering means, preferably with a tolerance of 0.05mm. The centering means can then be removed if desired. If the centering means 20 makes a tight fit, a form of gripping allows to extract it with a suitable extraction tool. The extraction effort can be high.

A second mounting method is described below. In a first step, a sealing member is formed by combining a seal ring 3 with a lip seal 4, and optionally with a reinforced seal 5 typically comprising an O-ring 52 and a pad 51. (Alternatively , the lip seal 4 is fitted on a shaft 1 or a hoop 2, and the seal ring 3 is then added thereto, then forming the sealing element.) Then said sealing member is positioned around a shaft 1, or where appropriate around a hoop 2, in contact with a flat surface such as a housing or a brake flange, with reference to the example shown in FIGS. 1 and 9. The centering means 7, typically a ring are mounted on the seal ring 3, on the hoop 2 or on the shaft 1 to ensure the contacting of the seal ring 3 with the hoop 2 or the shaft 1. The assembly is advantageously made tight, for example by means of a press that allows realizing a clearance-free assembly between the ferrule 2 and the centering means 7 and / or between the seal ring 3 and the centering means 7.

The positioning of the sealing element is automatically achieved thanks to the centering means 7 which make it possible, by virtue of the floating assembly as defined previously of said sealing element on the flat surface, to position the sealing means with respect to the shaft 1 or if necessary on the hoop 2, which thus allows to adjust the positioning before fixing. Then fixing said sealing member via fastening means in a position defined by said centering means, preferably with a tolerance of 0.05mm. The centering means can then be removed if desired. If the centering means 20 makes a tight fit, a form of gripping allows to extract it with a suitable extraction tool. The extraction effort can be high.

According to another variant of a method implementing an assembly such as that shown in FIG. 8, the user can arrange the assembly consisting of the hoop 2, the seal ring 3, the lip seal 4 and the sealing means. centering 7 on the shaft 1. For this, it is equipped with the assembly already assembled, and mounted on the shaft 1, typically exerting a force on the hoop 2; the other elements (the seal ring 3, the lip seal 4 and the centering means 7) are tightly mounted on the band 2 and are thus moved together.

Claims (13)

REVENDICATIONS1. System for producing a dynamic seal of a hydrostatic motor (M) intended to be mounted on a shaft (1), said system being characterized in that it comprises: - a sealing element comprising a support (3 ) and a dynamic sealing means (4), said support (3) being provided with a centering surface (37) with respect to a shaft (1), - centering means (7) of said sealing element relative to said shaft (1), - fixing means (6) of said support (3) on a flat support in a position defined by said centering means (7), said centering means (7) being adapted to mount said sealing member floating on said flat support relative to the shaft (1) before attachment to said flat support. 2. System according to claim 1, wherein said centering means (7) are adapted to allow a centering of said sealing element with a tolerance of 0.05mm with respect to said shaft (1). 3. System according to one of claims 1 or 2, wherein said sealing member comprises - a seal ring holder (3) forming said support, - a lip seal (4) forming said dynamic sealing means, said lip seal (4) being positioned in said seal carrier ring (3) via a holding surface (34) of said seal carrier ring (3), - a centering surface (37), said surface being positioned with a tolerance of of the order of 0.02mm with respect to the holding surface (34). 4. System according to one of claims 1 to 3, further comprising a friction track (2) adapted to be mounted on the shaft (1), said sealing member being mounted around the friction track (2). ), so that the dynamic sealing means (4) is frictionally mounted on said friction track (2). 5. System according to one of claims 1 to 3, respectively 4, wherein said centering means (7) comprise a ring adapted to be disposed in contact with said support (3) on the one hand, and on the other hand to contact of the shaft (1), respectively of the friction track (2) - 6. System according to one of claims 1 to 3, respectively 4 or 5, wherein said support (3) further comprises a housing in which are disposed a static seal (52) tightly mounted on a friction pad (51), said friction pad (51) being adapted to be tightly mounted on the shaft (1), respectively the friction track (2), so as to isolate said dynamic sealing means (4) from said hydrostatic motor (M). 7. System according to claim 6, wherein said support (3) arranges an internal space between said dynamic sealing means (4) and said housing, said internal space being connected to a pressure relief duct (16 and 17, or 18 and 19). 8. System according to one of claims 1 to 7, wherein said centering means (7) project from said sealing member and have a gripping area adapted to allow their removal after fixing said sealing member. The system of claim 8, wherein said gripping zone is adapted to prevent mounting of a hydrostatic motor (M). 10. Together for the realization of a dynamic sealing of a motor (M) intended to be mounted on a shaft (1), comprising: - a friction track (2), - a sealing element mounted around said track friction device (2), comprising a support (3) and a dynamic sealing means (4), said support (3) being provided with a centering surface (37), - centering means (7), - fastening means (6) of said support (3) in a defined position, said centering means (7) being arranged in contact with the friction track (2) on the one hand, and the support (3) on the other go. 11. The assembly of claim 10, wherein said centering means (7) are mounted tight relative to said friction track (2) and said support (3), so as to form an assembly adapted to be integrally mounted on a tree (1). 12. A method of producing a dynamic seal of a hydrostatic motor (M) mounted on a shaft (1), comprising the steps of: - positioning a sealing element around said shaft (1), floating against a plane support, said sealing element comprising a support (3) associated with a dynamic sealing means (4), and being associated with centering means (7), - adjusting the positioning of said sealing element relative to said shaft (1), - fixing said sealing element via fastening means (6), in a position defined by said centering means (7). The method of claim 12, further comprising a step of disposing a friction track (2) on the shaft (1), said sealing member being mounted around said friction track (2) -30