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 shrink-fitted onto the shafts so that they maintain their centering during operation in order not to generate imbalance and to provide support at certain axial stations to optimize the overall dynamic behavior.

[0003] However, shrink-fit mounting considerably complicates the assembly and disassembly of the 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 one rotor part to rotate relative to the other rotor part with which it is shrink-fitted, and significant thermal expansion of an external rotor part can create undesirable clearance between that part and the internal rotor part onto which it is shrink-fitted.

[0004] There is therefore a need for a device to maintain centering of concentric rotor parts, but without using shrink fittings between them. Such a centering device is notably provided in a longitudinally extending section where the two rotor parts are spaced apart. 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 whose operating principle is based both on the use of the centrifugal force of the rotating rotor parts and on the use of the vibrations suffered by said rotor parts to move movable wedges along an inclined ramp to a high clamping position where said movable wedges radially hold the two rotor parts in a centered position.

[0006] One aspect of the invention relates to an assembly consisting 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 spaced apart, the centering device being characterized in that it comprises at least three grooves, each equipped with a movable wedge, 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 to the external radial face of the internal rotor part, in the part where the two rotor parts are spaced apart; • each groove has a bottom inclined longitudinally at an angle α with respect to the X-X' axis 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 away from the external rotor part and a high position where it is supported both against the bottom and against an internal face of the external rotor part; • Each movable wedge has an internal sliding face bearing 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 wedges 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 lower position, i.e., in the lowest part of the groove (where the edges bordering the groove are highest), to their upper position, i.e., towards the raised part of the groove (where the edges bordering the groove are lowest). Once in the upper position, the movable wedges become wedged between the bottom of the groove and the inner face of the outer rotor part, and consequently radially immobilize the two rotor parts in a centered position to prevent them from becoming misaligned.

[0008] The invention also allows rotor parts to be mounted with a clearance which is filled when said rotor parts are rotated.

[0009] In addition to the characteristics mentioned in the preceding paragraph, the assembly according to one aspect of the invention may have one or more complementary characteristics from 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 opposite direction 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 a yield strength 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 general shape parallelepiped. • The movable wedges 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 such as previously described.

[0011] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0012] The figures are presented for illustrative purposes only and are not intended to limit the invention. In the figures, the dimensions are given for illustrative purposes only, some distances between the parts being intentionally exaggerated for clarity.

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

[0014] [Fig.2] is a view similar to [Fig.1] where the movable wedge is shown in an intermediate position and moved radially outwards by centrifugal force.

[0015] [Fig.3] is a view similar to [Fig.1] where the movable wedge is shown in the high position, where the two rotor parts are radially immobilized in the centered position.

[0016] [Fig.4] is a schematic partial perspective view illustrating a movable wedge and a groove in the 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 lower position.

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

[0019] [Fig.7] is a schematic cross-sectional view of two concentric rotor parts 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 lower position.

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

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

[0023] By convention, in this application, the term "longitudinal" or "axial" refers to a direction parallel to the longitudinal axis X-X' along which the turbomachine extends, while the term "radial" refers to a direction along a radius, that is, substantially perpendicular to the longitudinal axis X-X'. Furthermore, in this application, the terms "inner" and "outer," and "internal" and "external," are defined radially with respect to the longitudinal axis X-X'. Thus, a cylindrical part extending along the longitudinal axis X-X' has an inner radial face facing the longitudinal axis X-X' of the turbomachine and an outer radial face opposite its inner face and facing outwards. It should be noted that the longitudinal axis X-X' is the same for the rotor parts mentioned in the description.

[0024] As shown in [Fig.1] 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 internal rotor part 2 and an external rotor part 3 located around the internal 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 together at a portion not shown in the figures, this assembly being able to exhibit some play, and are spaced apart in another portion extending longitudinally and shown in the figures. The centering device 1 is provided in this other portion to maintain the centering of the rotor parts 2, 3 relative to each other around the axis X-X'. In the absence of this centering device 1, misalignment and / or offset of one of the rotor parts 2, 3 could, 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 can for example be a disc, a ring, a trunnion, 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 internal rotor part 2 can be solid or hollow. For example, it can be a disc or a ring, but also a shaft or a rotating axis.

[0029] The centering device 1 is distinguished 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 in it.

[0030] As shown in [Fig.1] 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 formed 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 spaced apart. The grooves 6, each equipped with a movable shim 5, are preferably distributed radially around the axis X-X', in particular to avoid imbalances in the internal rotor part 2. As illustrated by way of example in [Fig. 5] to [Fig. 8], the movable shims 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 with respect to the X-X' axis and forming a sliding ramp for the movable wedge 5 with which it is fitted. 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. Since this angle α is small, it can be considered that each movable wedge 5 slides longitudinally in a groove 6 along an axis substantially parallel to the X-X' axis.

[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 lowest point and a height H at the highest point, with H > h.

[0035] Fig. 2 also shows 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 spaced apart. The average radial height E is obtained by averaging the distance from the inner sliding face 12 to the face external clamping face 13 of the movable wedge 5 at its highest end, and the distance from the internal sliding face 12 to the external clamping 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 lower 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 higher position, located in the upper part of the sliding ramp, where it bears against both the bottom 10 and 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 lower 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 upper 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 a centered position to prevent them from becoming off-center.

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

[0039] An equivalent geometry exists in the case where the grooves 6 are directly formed on the external radial face 7 of the internal rotor part 2. Thus, if we denote 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 (see [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 clamping face 13 (upper face) located opposite the internal radial face 11 of the external rotor part 3 and coming into contact with it in the upper position.

[0041] The inner sliding face 12 is inclined longitudinally at an angle θ3 with respect to the outer clamping face 13 (see [Fig. 4]). The angle θ3 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 θ3 and the angle α have the same absolute value, so that when the movable wedges 5 are in the raised position, their inner sliding face 12 is parallel to the bottom 10 of the groove 6 in which they are housed, and their outer clamping face 13 is parallel to the inner radial face 11 of the outer rotor part 3, for a larger surface area of friction of the movable wedge 5 with the bottom 10 and the external rotor part 3, and therefore a better radial immobilization of the two rotor parts 2, 3.

[0042] Each movable wedge 5 preferentially has oriented reliefs 14 on its external clamping face 13, these reliefs being intended to promote the axial movement of the movable wedges 5 towards their upper position when subjected to vibrations. By oriented reliefs 14 are meant raised shapes formed on the external clamping face 13 of the movable wedges 5 and having an inclined portion oriented longitudinally such that when the movable wedges 5 come 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 move up the ramp at the bottom 10 of the grooves 6 and thus to move towards their upper 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 opposite direction to the direction in which the bottom 10 is inclined. The oriented reliefs 14 are preferably inclined in the opposite direction 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 operating conditions and have, for example, a yield strength 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 a generally parallelepiped shape, that is to say, of an overall parallelepiped shape, with some slight possible dimensional variations that substantially alter the general parallelepiped shape. Thus, the lateral sides 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 though it is a right prism with one base being an isosceles trapezoid, remains substantially parallelepiped in the sense of the invention.

[0045] As shown in [Fig. 1] and [Fig. 5], when the rotor parts 2, 3 are at rest, the movable wedges 5 of the invention are in a lowered position, resting in the bottom 10 of their respective groove 6. When the rotor parts 2, 3 are rotated about 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 upwards. 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 wedge themselves by friction between the rotor parts 2, 3 so as to immobilize them radially in a centered position (see [Fig.3]).

[0046] Disassembly of the rotor parts 2 and 3 is simple; just pull axially on the outer rotor part 3 in the direction opposite to the upper part of the ramp. The movable wedges 5 are then driven by the outer rotor part 3 and are easily extracted due to their 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 raised 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 the use of a centering device 1 according to the invention is illustrated in [Fig. 9], where the internal rotor part 2 is a shaft, the external rotor part 3 is a journal, and the grooves 6 are each formed in a grooved ring 9 press-fitted onto the internal rotor part 2, the external rotor part 3 being assembled with the internal rotor part 2 by splines 16, and immobilized longitudinally by a locking piece 17, for example, screwed or press-fitted. By way of example, the locking piece 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

Demands

1. Assembly (4) consisting 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 portion extending longitudinally where the two rotor parts (2, 3) are spaced apart, the centering device (1) comprising 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 portion where the two rotor parts (2, 3) are spaced apart;- each groove (6) has a bottom (10) inclined longitudinally at an angle α with respect 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 is supported 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) supported against the bottom (10) and an external clamping 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 θ with respect to the external clamping face (13); - the grooves (6) each equipped with a movable wedge (5) are distributed radially around the axis (X-X');and characterized in that - at least one movable wedge (5) has oriented reliefs (14) on its external wedging face (13).;

2. Assembly (4) according to claim 1, characterized in that oriented reliefs (14) are in the form of teeth (15), barbs or inclined blades, these oriented reliefs (14) being inclined in the opposite direction to the direction in which the bottom (10) is inclined.

3. 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.

4. 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.

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

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

7. 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.

8. 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 generally parallelepiped in shape.

9. 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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