Self-centering device for centering rotor parts

Abstract

Self-centering device for centering rotor parts. Centering device (1) for an internal rotor part (2) and an external rotor part (3) concentric and centered about a longitudinal axis (X-X'), said device comprising at least three grooves (6), each equipped with a movable wedge (5). Each groove (6) is located on an external radial face (7) of the internal rotor part (2) and has an inclined bottom (10) where a movable wedge (5) is mounted to slide longitudinally between a lower position where it is at a distance from the external rotor part (3) and a higher position where it is in axial restraint both against the bottom (10) of the groove (6) in which it is housed and against an internal face (11) of the external rotor part (3). The grooves (6), each equipped with a movable wedge (5), are distributed radially about the axis (X-X'). Figure to be published with the abbreviation: Figure 1

Description

Title of the invention: Self-centering device for centering rotor parts TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of centering devices provided between two concentric rotor parts for centering said parts. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0002] In a rotating machine, for example a turbomachine, rotor parts are usually shrunk onto the shafts so that they retain their centering during operation to avoid generating unbalance and to provide support at certain axial stations to optimize the overall dynamic behavior.

[0003] However, shrink-fitting considerably complicates the assembly and disassembly of rotor parts. Furthermore, the centering effectiveness of a shrink-fit assembly varies depending on the speed of the rotating machine and the temperature of the parts thus assembled. Indeed, a high speed can cause rotation of one rotor part relative to the other rotor part with which it is shrink-fitted, and strong thermal expansion of an outer rotor part can create unwanted play between this part and the inner rotor part onto which it is shrink-fitted.

[0004] There is therefore a need for a device for maintaining centering of concentric rotor parts, but without using hooping between them. Such a centering device is in particular provided in a longitudinally extending portion where the two rotor parts are at a distance from each other. Summary of the invention

[0005] In order to provide a solution to the problems mentioned above, the invention provides a centering device provided between two rotor parts and the operating principle of which is based both on the use of the centrifugal force of the rotor parts subject to rotation and on the use of the vibrations experienced by said rotor parts to move movable wedges along an inclined ramp to a high wedging position where said movable wedges radially hold the two rotor parts in the centered position.

[0006] One aspect of the invention relates to an assembly formed of an inner rotor part, an outer rotor part and a centering device for the rotor parts, the two rotor parts being concentric and centered around a longitudinal axis X-X', assembled with each other and having a longitudinally extending portion where the two rotor parts are at a distance from each other, the centering device being characterized in that it comprises at least three grooves each equipped with a shim mobile, and in that: • each groove is located on an external radial face of the internal rotor part or on the external radial face of a grooved ring fixed on the external radial face of the internal rotor part, in the part where the two rotor parts are at a distance from each other; • each groove has a bottom inclined longitudinally at an angle a relative to the axis X-X' and forming a sliding ramp for a movable wedge; • each movable wedge is mounted to slide longitudinally in a groove between a low position where it is at a distance from the external rotor part and a high position where it rests both against the bottom and against an internal face of the external rotor part; • each movable wedge has an internal sliding face resting against the bottom and an external wedging face opposite the internal face of the external rotor part, the internal sliding face being inclined longitudinally at an angle [3 relative to the external wedging face; and • the grooves, each equipped with a movable wedge, are distributed radially around the axis.

[0007] Thanks to the invention, when the rotor parts are rotated, the movable shims are moved radially outwards and, with the vibrations of said rotor parts, slide in the bottom of the groove where each is housed from their low position, that is to say in the lowest part of the groove (where the edges bordering the groove are the highest), towards their high position, that is to say in the direction of the raised part of the groove (where the edges bordering the groove are the lowest). Arriving in the high position, the movable shims are wedged between the bottom of the groove and the internal face of the external rotor part, and consequently immobilize the two rotor parts radially in the centered position in order to prevent them from becoming off-center.

[0008] The invention also makes it possible to mount rotor parts with a clearance which is filled when said rotor parts are rotated.

[0009] In addition to the characteristics which have just been mentioned in the preceding paragraph, the assembly according to one aspect of the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations: • At least one movable wedge has oriented reliefs on its external wedging face. • Oriented reliefs are in the form of inclined teeth, barbs or blades, these oriented reliefs being inclined in the direction opposite to the direction in which the bottom is inclined. • The angle a is between 0.1 and 30 degrees, preferably between 0.5 and 15 degrees and preferably between 1 and 5 degrees. • The angle [3 is between 0.1 and 30 degrees, preferably between 0.5 and 15 degrees and preferably between 1 and 5 degrees. • Angle a and angle [3 have the same absolute value. • At least one movable wedge is rigid and has an elastic limit of between 1800 and 2500 MPa, preferably between 1900 and 2300 MPa and more preferably between 1950 and 2050 MPa. • At least one movable wedge is made of steel, silicon carbide or inconel. • At least one movable wedge and the groove in which it slides are shaped general parallelepiped. • The movable shims and the grooves in which they slide are distributed uniformly and radially around the X-X' axis.

[0010] Another aspect of the invention relates to a rotating machine comprising an assembly as previously described.

[0011] The invention and its various applications will be better understood upon reading the description which follows and the examination of the figures which accompany it. BRIEF DESCRIPTION OF THE FIGURES

[0012] The figures are presented for information purposes only and do not limit the invention in any way. In the figures, the dimensions are given for illustrative purposes only, with certain distances between the parts being deliberately exaggerated for clarity.

[0013] [Fig-1] is a partial schematic view in longitudinal section of two rotor parts concentric equipped with an example of a centering device according to the invention, where a movable wedge is shown in the low position at the bottom of a groove.

[0014] [Fig.2] is a view similar to [Fig.l] where the movable wedge is shown in an intermediate position and moved radially outwards by the centrifugal force.

[0015] [Fig.3] is a view similar to [Fig.l] where the movable wedge is shown in the high position, where the two rotor parts are immobilized radially in the centered position.

[0016] [Fig.4] is a partial schematic perspective view illustrating a movable wedge and a groove in a dissociated state.

[0017] [Fig.5] is a schematic cross-sectional view of two concentric rotor parts equipped with an example of a centering device according to the invention comprising six movable wedges shown in the low position.

[0018] [Fig.6] is a view similar to [Fig.5] where the six movable wedges are in the upper position.

[0019] [Fig.7] is a schematic cross-sectional view of two rotor parts concentric equipped with an example of a centering device according to the invention comprising four movable wedges shown in the lower position.

[0020] [Fig-8] is a schematic cross-sectional view of two concentric rotor parts equipped with an example of a centering device according to the invention comprising three movable wedges shown in the low position.

[0021] [Fig.9] of two concentric rotor parts equipped with an example of a centering device according to the invention, where the outer rotor part is a journal mounted on the inner rotor part by splines and immobilized longitudinally by a threaded nut screwed onto the inner rotor part. DETAILED DESCRIPTION

[0022] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0023] By convention, in the present application, the term "longitudinal" or "axial" corresponds to a direction parallel to the longitudinal axis X-X' along which the turbomachine extends, while the term "radial" means a direction directed along a radius, that is to say substantially perpendicular to the longitudinal axis X-X'. Furthermore, in the present application, the terms "inner" and "outer", and "inner" and "outer" are defined radially relative to the longitudinal axis X-X'. Thus, a cylindrical part extending along the longitudinal axis X-X' comprises an inner / inner radial face facing the longitudinal axis X-X' of the turbomachine and an outer / outer radial face, opposite its inner face and facing outwards. It will be noted that the longitudinal axis X-X' is the same for the rotor parts cited in the description.

[0024] As shown in [Fig.l] to [Fig.9], the invention relates to a centering device 1 provided between two concentric rotor parts 2, 3 centered around an axis X-X', namely an inner rotor part 2 and an outer rotor part 3 located around the inner rotor part 2. The invention also relates to an assembly 4 comprising two rotor parts 2, 3 and a centering device 1.

[0025] The two rotor parts 2, 3 are assembled with each other at a part not illustrated in the figures, this assembly possibly having a certain play, and are at a distance from each other in another part extending longitudinally and illustrated in the figures. The centering device 1 is provided in this other part in order to maintain the centering of the rotor parts 2, 3 between them around the axis X-X'. In the absence of this centering device 1, a decentering and / or misalignment of one of the rotor parts 2, 3 can in particular cause an imbalance in the rotating machine comprising said rotor parts 2, 3.

[0026] The two rotor parts 2, 3 are preferably parts of revolution, for example of round section.

[0027] The external rotor part 3 may for example be a disc, a ring, a journal, or any other part assembled with an internal rotor part 2 and extending longitudinally along the axis X-X' of these rotor parts 2, 3.

[0028] The inner rotor part 2 may be solid or hollow. For example, it may be a disc or a ring, but also a shaft or a rotating axis.

[0029] The centering device 1 is characterized in that it comprises movable wedges 5 each mounted in a groove 6. Each movable wedge 5 is housed in a groove 6 so as to be able to slide longitudinally therein.

[0030] As shown in [Fig.l] to [Fig.3], each groove 6 can be provided in the external radial face 8 of a grooved ring 9 fixed on the external radial face 7 of the internal rotor part 2, for example by shrink fitting.

[0031] As shown in [Fig.4] to [Fig.8], each groove 6 can also be shaped directly in the external radial face 7 of the internal rotor part 2. This can however weaken the internal rotor part 2.

[0032] Each groove 6 is located in the part where the two rotor parts 2, 3 are at a distance from each other. The grooves 6, each equipped with a movable wedge 5, are preferably distributed radially around the axis X-X', in particular in order to avoid imbalances in the internal rotor part 2. As illustrated by way of example in [Fig.5] to [Fig.8], the movable wedges 5 and the grooves 6 in which they slide are preferably distributed uniformly and radially around the axis X-X'.

[0033] Each groove 6 has a bottom 10 inclined longitudinally at an angle α relative to the axis X-X' and forming a sliding ramp for the movable wedge 5 with which it is equipped. The bottom 10 thus has a low point in the lower part of said groove 6 (on the left in the figures) and a high point in the upper part thereof (on the right in the figures). The angle α is for example between 0.1 and 30 degrees, preferably between 0.5 and 15 degrees and preferably between 1 and 5 degrees. This angle α being small, it can be considered that each movable wedge 5 slides longitudinally in a groove 6 along an axis substantially parallel to the axis X-X'.

[0034] As shown in [Fig.2], when the grooves 6 are each formed in a grooved ring 9, the bottom 10 of each groove 6 has a height h at the low point and a height H at the high point, with H > h.

[0035] In [Fig. 2] also appear the average radial height E of a movable wedge 5, as well as the radial distance D separating rotor parts 2, 3 centered in the part where they are at a distance from each other. The average radial height E is obtained by taking the average between the distance from the internal sliding face 12 to the external wedging face 13 of the movable wedge 5 at its highest end, and the distance from the internal sliding face 12 to the external wedging face 13 of the movable wedge 5 at its lowest end.

[0036] Each movable wedge 5 is mounted to slide longitudinally in a groove 6 between a low position, located in the lower part of the sliding ramp, where it is at a distance from the external rotor part 3 (see [Fig. 1]) and a high position, located in the upper part of the sliding ramp, where it bears both against the bottom 10 and against an internal radial face 11 of the external rotor part 3 [Fig. 3]. An intermediate position is shown in [Fig. 2].

[0037] Thus, in the low position, each movable wedge 5 can move freely radially between the bottom 10 of the groove 6 where it is housed and the internal radial face 11 of the external rotor part 3, while in its high position each movable wedge 5 is wedged between the bottom 10 of the groove 6 and the internal radial face 11 of the external rotor part 3, radially immobilizing the two rotor parts in the centered position in order to prevent them from becoming off-center.

[0038] For this purpose, we have: • h + E < D ; and • H + E>D.

[0039] An equivalent geometry exists in the case where the grooves 6 are directly shaped on the external radial face 7 of the internal rotor part 2. Thus, if we designate by P the depth of the grooves 6 in their deepest part, and by p the depth of the grooves 6 in their shallowest part, with P > p (cf. [Fig.4]), we have: • E - P < D, and • E - p > D.

[0040] Each movable wedge 5 has an internal sliding face 12 (lower face) intended to bear against the bottom 10 and an external wedging face 13 (upper face) located opposite the internal radial face 11 of the external rotor part 3 and coming into contact against the latter in the high position.

[0041] The internal sliding face 12 is inclined longitudinally at an angle [3 relative to the external wedging face 13 (see [Fig.4]). The angle [3 is for example between 0.1 and 30 degrees, preferably between 0.5 and 15 degrees and preferably between 1 and 5 degrees. Preferably, the angle [3 and the angle a have the same absolute value, so that when the movable wedges 5 are in the high position, their internal sliding face 12 is parallel to the bottom 10 of the groove 6 in which they are housed and their external wedging face 13 is parallel to the internal radial face 11 of the external rotor part 3, for a larger friction surface of the movable wedge 5 with the bottom 10 and the external rotor part 3, and therefore better radial immobilization of the two rotor parts 2, 3.

[0042] Each movable wedge 5 preferably has oriented reliefs 14 on its external wedging face 13, these reliefs having the purpose of promoting axial displacement movable wedges 5 towards the high position when they are subjected to vibrations. By oriented reliefs 14 is meant relief shapes formed on the external wedging face 13 of the movable wedges 5 and having an inclined part oriented longitudinally so that when the movable wedges 5 come into abutment against the internal radial face 11 of the external rotor part 3 under the effect of vibrations, these oriented reliefs 14 tend to encourage the movable wedges 5 to rise up the ramp of the bottom 10 of the grooves 6 and therefore to move towards their high position. The oriented reliefs 14 are preferably in the form of inclined teeth 15, inclined barbs or inclined blades, said oriented reliefs 14 being inclined in the direction opposite to the direction in which the bottom 10 is inclined. The oriented reliefs 14 are preferably inclined in the direction opposite to that of the mounting of the movable wedges 5 in their respective groove 6.

[0043] The movable shims 5 are preferably rigid under normal conditions of use, and have, for example, an elastic limit of between 1800 and 2500 MPa, preferably between 1900 and 2300 MPa and more preferably between 1950 and 2050 MPa. The movable shims 5 may, for example, be made of metal or ceramic. They are preferably made of steel, silicon carbide or inconel.

[0044] The movable wedges 5 and the grooves 6 in which they slide are preferably of generally parallelepiped shape, that is to say of overall parallelepiped shape, with some slight possible dimensional variations which substantially alter the general parallelepiped shape. Thus, the lateral flanks of the grooves 6 are preferably flared outwards so as to guide the movement of the movable wedges 5 when they return to the bottom 10 of the groove 6 in which they are housed (see [Fig. 4]). The grooves 6 thus have a trapezoidal cross-sectional profile, but their general shape, even if it is a right prism whose base is an isosceles trapezoid, remains substantially parallelepiped within the meaning of the invention.

[0045] As shown in [Fig.l] and [Fig.5], when the rotor parts 2, 3 are at rest, the movable wedges 5 of the invention are in the low position, resting in the bottom 10 of their respective groove 6. When the rotor parts 2, 3 are rotated around the axis X-X', under the action of centrifugal force, the movable wedges 5 of the invention move radially outwards, towards the external rotor part 3, and under the effect of vibrations, move axially towards the top of the ramp, towards their high position (see [Fig.2] and [Fig.6]), this movement being encouraged by the presence of the oriented reliefs 14 of the movable wedges 5. Finally, the movable wedges 5 of the invention reach their high position, where they are wedged by friction between the rotor parts 2, 3 so as to immobilize them radially in the centered position (see [Fig.3] )•

[0046] Disassembly of the rotor parts 2, 3 is simple; it is sufficient to pull axially on the external rotor part 3 in the direction opposite to the upper part of the ramp. The movable wedges 5 are then driven by the external rotor part 3 and are easily extracted due to the inclined bearing surfaces.

[0047] As shown in [Fig.8], the centering device 1 comprises at least three movable wedges 5 so that, when the movable wedges 5 are in the high position, the rotor parts 2, 3 are mutually immobilized in all radial positions. As shown by way of example in [Fig.5] to [Fig.7], the centering device 1 may comprise any number of movable wedges 5, as long as this number is greater than or equal to three.

[0048] A concrete example of use of a centering device 1 according to the invention is illustrated in [Fig.9], where the inner rotor part 2 is a shaft, where the outer rotor part 3 is a journal and where the grooves 6 are each shaped in a grooved ring 9 shrunk onto the inner rotor part 2, the outer rotor part 3 being assembled with the inner rotor part 2 by grooves 16, and immobilized longitudinally by an immobilizing part 17, for example screwed or shrunk. By way of example, the immobilizing part 17 is a threaded nut.

[0049] Another aspect of the invention relates to a rotating machine comprising an assembly 4 of the invention, this rotating machine being able for example to be a turbomachine, a pump, a compressor, a reducer, a turbocharger, etc.

Claims

Claims

1. Assembly (4) formed of an inner rotor part (2), an outer rotor part (3) and a centering device (1) for the rotor parts (2, 3), the two rotor parts (2, 3) being concentric and centered around a longitudinal axis (X-X'), assembled with each other and having a longitudinally extending part where the two rotor parts (2, 3) are at a distance from each other, the centering device (1) being characterized in that it comprises at least three grooves (6) each equipped with a movable wedge (5), and in that: - each groove (6) is located on an outer radial face (7) of the inner rotor part (2) or on the outer radial face (8) of a grooved ring (9) fixed on the outer radial face (7) of the inner rotor part (2), in the part where the two rotor parts (2, 3) are at a distance one from the other;- each groove (6) has a bottom (10) inclined longitudinally at an angle α relative to the axis (X-X') and forming a sliding ramp for a movable wedge (5); - each movable wedge (5) is mounted to slide longitudinally in a groove (6) between a low position where it is at a distance from the external rotor part (3) and a high position where it bears both against the bottom (10) and against an internal radial face (11) of the external rotor part (3); - each movable wedge (5) has an internal sliding face (12) bearing against the bottom (10) and an external wedging face (13) opposite the internal radial face (11) of the external rotor part (3), the internal sliding face (12) being inclined longitudinally at an angle [3 relative to the external wedging face (13); and - the grooves (6) each equipped with a movable wedge (5) are distributed radially around the axis (X-X').;

2. Assembly (4) according to claim 1, characterized in that at least one movable wedge (5) has oriented reliefs (14) on its external wedging face (13).

3. Assembly (4) according to claim 2, characterized in that oriented reliefs (14) are in the form of teeth (15), barbs or blades inclined, these oriented reliefs (14) being inclined in the direction opposite to the direction in which the bottom (10) is inclined.

4. Assembly (4) according to any one of the preceding claims, characterized in that the angle a is between 0.1 and 30 degrees, preferably between 0.5 and 15 degrees and preferably between 1 and 5 degrees.

5. Assembly (4) according to any one of the preceding claims, characterized in that the angle [3 is between 0.1 and 30 degrees, preferably between 0.5 and 15 degrees and preferably between 1 and 5 degrees.

6. Assembly (4) according to any one of the preceding claims, characterized in that the angle α and the angle [3 have the same absolute value.

7. Assembly (4) according to any one of the preceding claims, characterized in that at least one movable wedge (5) is rigid and has an elastic limit of between 1800 and 2500 MPa, preferably between 1900 and 2300 MPa and more preferably between 1950 and 2050 MPa.

8. Assembly (4) according to any one of the preceding claims, characterized in that at least one movable wedge (5) is made of steel, silicon carbide or inconel.

9. Assembly (4) according to any one of the preceding claims, characterized in that at least one movable wedge (5) and the groove (6) in which it slides are of generally parallelepiped shape.

10. Assembly (4) according to any one of the preceding claims, characterized in that the movable wedges (5) and the grooves (6) in which they slide are distributed uniformly and radially around the axis (X-X').

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