Bearing

Abstract

A semi-floating ring bearing 26 having body 54 extending along axis 56 from first 58 to second end 60 and a flange 64 on the first end 58. The flange 64 engages stop plate 28 to restrict rotational mo

Description

Field of Invention The present invention relates to a semi-floating ring bearing for a turbomachine. The present invention also relates to a semi-floating ring bearing assembly for a turbomachine, to a turbomachine, and to a method of assembling a semi-floating ring bearing. Background Turbochargers are well known devices for supplying air to the intake of an internal combustion engine at pressures above atmospheric pressure (boost pressures). A conventional turbocharger comprises an exhaust-gas-driven turbine wheel mounted on a rotatable shaft within a turbine housing. Rotation of the turbine wheel drives rotation of the compressor wheel mounted on the other end of the shaft within the compressor cover. The compressor wheel delivers compressed air to the intake manifold of the engine, thereby increasing engine power. The turbocharger shaft is conventionally supported by a semi-floating ring bearing and thrust bearings, including appropriate lubricating systems, located within a central bearing housing connected between the turbine and compressor. The turbine housing and compressor housings are typically mounted to the bearing housing. Rotation and axial movement of semi-floating ring bearings are constrained in use. This is typically achieved by providing a locking pin that is secured to the bearing housing and extends into a hole provided in the body of the semi-floating ring bearing. Assembly of semi-floating ring bearings can be time consuming because it can be difficult for a user to locate the locking pin in the hole of the semi-floating ring bearing. The present invention seeks to address one or more problems associated with conventional semi-floating ring bearings, whether identified herein or otherwise. Summary In a first aspect of the invention there is provided a semi-floating ring bearing assembly for a turbomachine. The semi-floating ring bearing assembly comprises a bearing housing that comprises a bearing cavity; a stop plate; and a semi-floating ring bearing. The semi-floating ring bearing comprises a body that comprises a central axis, a first end, a second end, and an external surface. The semi-floating ring bearing further comprises a flange that is disposed at the first end of the body. The bearing housing and the flange define at least one pair of complementary features that cooperate to restrict axial movement of the semi-floating ring bearing. The stop plate and the flange define at least one pair of complementary features that cooperate to restrict rotational movement of the semi-floating ring bearing. The flange may extend radially beyond the external surface of the body. The semi-floating ring bearing may be receivable by the bearing cavity. The semifloating ring bearing may be disposed in the bearing cavity. The flange may encircle, or extend only part way around, the central axis. The at least one pair of complementary features that restrict rotational movement of the semi-floating ring bearing may be understood to mean that a degree of rotation of the semi-floating ring bearing is allowed, but is limited. Similarly, the at least one pair of complementary features that restrict axial movement of the semi-floating ring bearing may be understood to mean that a degree of axial movement of the semi-floating ring bearing is allowed, but is limited. Here and throughout this document, rotation of the semi-floating ring bearing may be understood to refer to rotation of the semi-floating ring bearing about the central axis. Here and throughout this document, axial movement of the semi-floating ring bearing may be understood to refer to a translation of the semi-floating ring bearing in a direction that is parallel to the central axis. Since the flange of the semi-floating ring bearing defines features that are complementary to the stop plate and bearing housing to restrict rotational and axial movement of the semi-floating ring bearing respectively, assembly of the semi-floating ring bearing into the bearing housing is advantageously simplified. This is because a user is able to readily locate the features of the flange during assembly to allow the semi-floating ring bearing to be correctly constrained in use. Furthermore, since the flange of the semi-floating ring bearing defines features that are complementary to the stop plate and bearing housing to restrict rotational and axial movement of the semi floating ring bearing respectively, fewer components are required to restrict movement of the semi-floating ring bearing, which further simplifies assembly of the semi-floating ring bearing assembly. The bearing housing may comprise a groove. The flange may be receivable by the groove to restrict axial movement of the semi-floating ring bearing. The groove may be integrally formed with the housing. Where the bearing housing comprises a groove and the flange is receivable by the groove to restrict axial movement of the semi-floating ring bearing, axial movement of the semi-floating ring bearing is restricted in a simple and robust manner. In a first configuration of the semi-floating ring bearing, the semi-floating ring bearing may be inserted into or withdrawn from the bearing cavity. In a second configuration of the semi-floating ring bearing, the flange of the semi-floating ring bearing may be received by the groove such that axial movement of the semi-floating ring bearing is restricted. Receipt of the flange by the groove constrains axial movement of the semi-floating ring bearing in a robust manner. This reduces the likelihood of axial movement of the semifloating ring bearing in use. The semi-floating ring bearing may be rotatable between the first configuration and the second configuration. Where the semi-floating ring bearing is rotatable between the first configuration and the second configuration, assembly of the semi-floating ring bearing assembly is more efficient. This is because a user only need rotate the semi-floating ring bearing to move it to the second configuration. A periphery of the flange may be non-axisymmetric to define at least one anti-rotation feature. The at least one anti-rotation feature may cooperate with at least one complementary anti-rotation feature of the stop plate. Where the periphery of the flange is non-axisymmetric to define at least one antirotation feature, rotation of the semi-floating ring bearing is readily constrainable. This is because a user can easily identify the anti-rotation feature and position the semifloating ring bearing accordingly. This makes assembly of the semi-floating ring bearing more efficient. In a plane that is perpendicular to the central axis, the periphery of the flange may be asymmetric. The periphery of the flange being asymmetric may be understood to mean that the periphery of the flange is asymmetric regardless of an orientation of a reference plane used to determine symmetry of the periphery of the flange. The reference plane being disposed on the central axis. Where the periphery of the flange is asymmetric in a plane that is perpendicular to the central axis, the flange acts as part of a poke-yoke mechanism when being inserted into a bearing housing. This advantageously assists the user with assembly of the semi-floating ring bearing into a bearing assembly. Therefore, where the periphery of the flange is asymmetric in a plane that is perpendicular to the central axis, assembly of the semi-floating ring bearing into a bearing housing is more efficient. The periphery of the flange may comprise at least one flat portion. The at least one flat portion may define the at least one anti-rotation feature. Where the periphery of the flange comprises at least one flat portion, the anti-rotation feature is particularly effective at preventing rotation of the semi-floating ring bearing in use. This is because the at least one flat portion provides a greater amount of contact with a corresponding abutment than, for example, if point contact were used. The stop plate may comprise at least one arm. The at least one arm may be configured to engage the at least one anti-rotation feature of the flange to restrict rotation of the semi-floating ring bearing when the semi-floating ring bearing is in the second configuration. Where the stop plate comprises at least one arm that is configured to engage the at least one anti-rotation feature, rotation of the semi-floating ring bearing can be constrained in a robust manner. The flange may define a major portion and a minor portion. The radius of the major portion may be greater than the radius of the minor portion. The radius of the minor portion may be equal to the radius of the external surface of the of the semi-floating ring bearing. An arc angle of the major portion may be at least 30 degrees and / or less than 150 degrees. Where the arc angle of the major portion is at least 30 degrees and / or less than 150 degrees, assembly of the semi-floating ring bearing into a bearing housing is more user friendly. This is because the semi-floating ring bearing can be readily positioned during assembly. Furthermore, the flange is able to withstand axial forces exerted upon it in use while restricting axial movement of the semi-floating ring bearing. The groove may define an arc angle. The arc angle of the groove may be greater than or equal to the arc angle of the major portion of the flange. Where the arc angle of the groove is greater than or equal to the arc angle of the major portion of the flange, contact between the groove and the major portion of the flange is maximised. This is desirable because axial loads exerted by the flange to the groove in use are distributed over a larger area, which decreases the stresses that the bearing housing is subject to in the region of the groove. This advantageously reduces the likelihood of wear and / or other damage to the bearing housing in use. The stop plate may define an oil baffle. Where the stop plate defines an oil baffle, assembly of the semi-floating ring bearing is more efficient. This is because an oil baffle does not need to be provided separately. A first axial end face of the body may define a thrust pad. Where the first axial end face of the body defines a thrust pad, assembly of the semifloating ring bearing is more efficient. This is because a thrust pad does not need to be provided separately. In a second aspect of the invention there is provided a semi-floating ring bearing for a turbomachine. The turbomachine comprises a bearing housing within which a stop plate is received. The semi-floating ring bearing comprises a body. The body comprises a central axis, a first end, a second end, and an external surface. The semifloating ring bearing further comprises a flange that is disposed at the first end of the body. When the semi-floating ring bearing is received by the bearing housing, the flange is configured to cooperate with the bearing housing to restrict axial movement of the semi-floating ring bearing and to cooperate with the stop plate to restrict rotational movement of the semi-floating ring bearing. The flange cooperates with both the bearing housing and the stop plate to restrict axial and rotational movement of the semi-floating ring bearing respectively. This advantageously simplifies assembly of the semi-floating ring bearing into the bearing housing because fewer components are required. The semi-floating ring bearing may be for a semi-floating ring bearing assembly for a turbomachine. The semi-floating ring bearing assembly may comprise a housing and a stop plate. The flange being disposed at the first end of the body may be understood to mean that the flange is disposed at the absolute end of the body, or in an end region of the body. The at least one anti-rotation feature may be configured to be engaged to restrict rotation of the semi-floating ring bearing in use. The flange may extend radially beyond the external surface of the body. A periphery of the flange may be non-axisymmetric to define at least one anti-rotation feature. The at least one anti-rotation feature of the flange may cooperate with at least one complementary anti-rotation feature of the stop plate. In a plane that is perpendicular to the central axis, the periphery of the flange may be asymmetric. The periphery of the flange may comprise at least one flat portion. The flange may define a major portion and a minor portion. The radius of the major portion may be greater than the radius of the minor portion. The radius of the minor portion may be equal to the radius of the external surface of the of the semi-floating ring bearing. An arc angle of the major portion may be at least 30 degrees and / or less than 150 degrees. A first axial end face of the body may define a thrust pad. In a third aspect of the invention there is provided a turbomachine comprising a semifloating ring bearing assembly. The turbomachine comprises a turbine, a compressor; and a semi-floating ring bearing assembly. The semi-floating ring bearing assembly comprises a bearing housing that is disposed between the turbine and the compressor. The bearing housing comprises a bearing cavity. The semi-floating ring bearing assembly further comprises a stop plate; and a semi-floating ring bearing. The semifloating ring bearing comprises a body that defines comprises a central axis, a first end, a second end, and an external surface. The semi-floating ring bearing further comprises a flange that is disposed at the first end of the body. The bearing housing and the flange define at least one pair of complementary features that cooperate to restrict axial movement of the semi-floating ring bearing. The stop plate and the flange define at least one pair of complementary features that cooperate to restrict rotational movement of the semi-floating ring bearing. The turbomachine may be a turbocharger. The flange may extend radially beyond the external surface of the body. A periphery of the flange may be non-axisymmetric to define at least one anti-rotation feature. The semi-floating ring bearing assembly may be a semi-floating ring bearing assembly according to the first aspect of the invention. Any of the features of the semi-floating ring bearing assembly disclosed in relation to the first aspect of the invention may be combined with the third aspect of the invention. In a fourth aspect of the invention there is provided a method of assembling a semifloating ring bearing assembly for a turbomachine. The method comprises providing a bearing housing that comprises a bearing cavity; providing a semi-floating ring bearing. The semi-floating ring bearing comprises a body that comprises a central axis, a first end, a second end, and an external surface; and a flange that is disposed at the first end of the body. The method further comprises inserting the semi-floating ring bearing into the bearing housing; and mounting a stop plate to the bearing housing. The bearing housing and the flange define at least one pair of complementary features that cooperate to restrict axial movement of the semi-floating ring bearing. The stop plate and the flange define at least one pair of complementary features that cooperate to restrict rotational movement of the semi-floating ring bearing. The method may comprise inserting the semi-floating ring bearing into the bearing cavity. The method may comprise securing the stop plate to the bearing housing. The bearing housing may comprise a groove. The method may further comprise, subsequent to inserting the semi-floating ring bearing into the bearing cavity, rotating the semi-floating ring bearing such that the flange is disposed in the groove to restrict axial movement of the semi-floating ring bearing. The stop plate may comprises at least one arm. The flange may define at least one anti-rotation feature. The stop plate may be secured to the bearing housing such that the at least one arm of the stop plate engages the at least one anti-rotation feature to restrict rotation of the semi-floating ring bearing. Brief Description of the Drawings Embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a cross-sectional view of a turbocharger; Figure 2 shows a cross-sectional view of a bearing housing of the turbocharger of Figure 1; Figure 3 shows a perspective view of a semi-floating ring bearing assembly of the turbocharger of Figure 1; Figure 4 shows a front view of the semi-floating ring bearing assembly of Figure 3; Figure 5 shows a front view of the bearing housing of Figure 2 with a semifloating ring bearing of the bearing assembly of Figure 3 disposed therein; Figure 6 shows a cross-sectional view of the bearing housing of Figure 2 with the semi-floating ring bearing assembly of Figure 3 disposed therein; and Figure 7 shows a front view of the bearing housing of Figure 2 with the bearing assembly of Figure 3 disposed therein. Detailed Description Figure 1 shows a cross-sectional view of a turbocharger 2. The turbocharger 2 comprises a turbine 4 joined to a compressor 6 via a central bearing housing 8. The turbine 4 comprises a turbine wheel 10 for rotation within a turbine housing 12. The turbine wheel 10 comprises blades 14 and is rotatable about a central axis 16 of the turbocharger 2. Similarly, the compressor 6 comprises a compressor wheel 17 (or “impeller”) that comprises blades 19 (only one of which is labelled in Figure 1) and can rotate within a compressor housing 18 about the central axis 16. The compressor housing 18 defines a compressor chamber 20 which is largely filled by the compressor wheel 17, and within which the compressor wheel 17 can rotate. The turbine wheel 10 and compressor wheel 17 are mounted on opposite ends of a common turbocharger shaft 22 which extends through the central bearing housing 8. The turbocharger shaft 22 is rotatably supported by a bearing assembly 24 that is disposed in the bearing housing 8. The bearing assembly 24 comprises a semi-floating ring bearing 26 and a stop plate 28. The bearing housing 8 provides a lubricating system for the turbocharger assembly. The bearing housing 8 includes a series of channels 30a-c, through which oil is supplied to the bearing assembly 24. A manifold 30a opens into a first oil line 30b, and a second oil line 30c. The channels 30a-c receive oil from an engine oil circuit (not shown). A compressor seal assembly 32 and a turbine seal assembly 34 are disposed in the bearing housing 8. The seal assemblies 32, 34 seek to prevent oil leaking out of the bearing housing 8 and either the turbine 4 or the compressor 6 respectively. The compressor seal assembly 32 comprises an oil seal plate 36 and an oil slinger 38. The turbine seal assembly 34 comprises seal members 40a, 40b that sealingly engage the turbocharger shaft 22 and the bearing housing 8. Figure 2 shows a cross-sectional view of the bearing housing 8. The bearing housing 8 defines a first cavity 42, a second cavity 44, and a third cavity 46. The first cavity 42 adjoins the third cavity 46. The second cavity 44 adjoins the third cavity 46. The third cavity 46 is disposed between the first cavity 42 and the second cavity 44. The compressor seal assembly (not shown in Figure 2) is receivable in the first cavity 42. Therefore, the first cavity 42 may be referred to as a compressor seal assembly cavity or as a first seal cavity. The turbine seal assembly (not shown in Figure 2) is receivable in the second cavity 44. Therefore, the second cavity 44 may be referred to as a turbine seal assembly cavity or as a second seal cavity. At least part of the semifloating ring bearing (not shown in Figure 2) is receivable in the third cavity 46. Therefore, the third cavity 46 may be referred to as a semi-floating ring bearing cavity or as a bearing cavity. The first cavity 42 defines a first surface 48, a second surface 49, and a third surface 51. The first surface 48 adjoins the third cavity 46. The second surface 49 is separated from the first surface 48 by an axially extending wall 53. The axially extending wall 53 extends between the first surface 48 and the second surface 49. A groove 52 extends into the axially extending wall 53. In use, the stop plate (not shown in Figure 2) abuts the second surface 49. A shoulder 59 is disposed between the second surface 49 and the third surface 51. In use, the oil seal plate (not shown in Figure 2) abuts the third surface 51. The oil seal plate also abuts the stop plate (not shown in Figure 2) in use. Figure 3 shows a perspective view of the semi-floating ring bearing assembly 24. The stop plate 28 defines a major portion 66. An aperture 68 extends through the major portion 66. A first arm 70 and a second arm 72 extend from the periphery of the aperture. The arms 70, 72 serve to restrict rotation of the semi-floating ring bearing 26 in use, as will be discussed in more detail below. Each arm comprises a respective first portion 74 (only one of which is labelled in Figure 3) and a respective second portion 76 (only one of which is labelled in Figure 3). The first portions 74 extend generally parallel to the central axis 56 and the second portions 76 extend radially inwards, towards the central axis 56. In some, non-depicted, embodiments, only a component of the length of the first portions need extend in a direction that is generally parallel to the central axis. In some, non-depicted, embodiments, only a component of the length of the second portions need extend in a radially inward direction. The first portions 74 may be referred to as proximal portions of the arms 70, 72. The second portions 76 may be referred to as distal portions of the arms 70, 72. The first and second portions 74, 76 define respective distal ends 77, 79 of the arms. The stop plate 28 comprises an oil baffle 63. The oil baffle 63 extends from the major portion 66. The semi-floating ring bearing 26 comprises a body 54. The body 54 defines a central axis 56. The body 54 defines a first end 58 and a second end 60. The first end 58 is disposed at an opposite end of the body 54 to the second end 60. The body 54 comprises a first end face 55. The body 54 comprises a second end face (not visible in Figure 3 - it is hidden by the body). The first end face 55 is generally opposed to the second end face. The first end face 55 and the second end face define respective thrust pads 57 (only the thrust pad of the first end face is visible in Figure 3). The thrust pads 57 are integrally formed with the body 54. However, in some embodiments, one or both of the end faces 55 need not define thrust pads 57. The body 54 defines an external surface 62. The external surface 62 of the body 54 is generally cylindrical. The semi-floating ring bearing 26 comprises a flange 64. The flange 64 is receivable by the groove 52 in use, as will be discussed in more detail below. The flange 64 is disposed at the first end 58 of the body 54. The flange 64 being disposed at the first end 58 of the body 54 may be understood to mean that the flange 64 is disposed at an absolute end of the body 54, or alternatively at an end region of the body 54. Where the flange 64 is disposed at an absolute end of the body 54, at least part of the flange may define at least part of the first end face 55. The flange 64 extends radially (with respect to the central axis 56) beyond the external surface 62 of the body 54 of the semi-floating ring bearing 26. The flange 64 encircles the central axis 56. However, in some embodiments, the flange 64 may extend only part way around the central axis 56. Referring to Figure 4, the flange 64 defines a major portion 71 and a minor portion 73. The radius of the major portion 71 is greater than the radius of the minor portion 73. The first flat portion 67 and the second flat portion 69 adjoin the major portion 71. The minor portion 73 of the flange 64 may be defined as the portion of the flange 64 that defines the minimum radius of the flange 64. In some embodiments, the radius of the minor portion 73 may be equal to the radius of the external surface 62 of the body 54. The major portion 71 defines an arc angle. The arc angle of the major portion may be at least 30° and / or less than 150°. The first flat portion 67 and the second flat portion 69 adjoin the minor portion 73. The arc angle of the major portion 71 may be defined as the angle between radial axes that intersect respective end points of a circumferential section of the flange 64 that defines the largest radius of the flange 64. Where the flange 64 extends only part way around the central axis 56, the minor portion 73 need not be provided, or the minor portion 73 may be said to have a radius that is equal to the radius of the external surface 62 of the body 54. In some embodiments, the flange may comprise a plurality of major portions and a plurality of minor portions, the plurality of minor portions being alternatively interspersed between the plurality of major portions. In this embodiment, a shape of the second surface 49 and of the axially extending wall 53 are complementary to the shape of the flange 64 to allow the flange 64 to enter the groove 52. A periphery 65 of the flange 64 is non-axisymmetric. This allows the periphery of the flange 64 to define an anti-rotation feature of the semi-floating ring bearing 26, as will be discussed in more detail below. In a plane that is perpendicular to the central axis (which extends into the page of Figure 4) the periphery 65 of the flange 64 is asymmetric. The plane may be the plane of view of Figure 4. The periphery 65 of the flange 64 is asymmetric regardless of an orientation of a reference plane that is used to determine symmetry of the periphery 65 of the flange 64. The periphery 65 of the flange 64 being asymmetric in this way allows the flange 64 to act as part of a poke yoke mechanism when being inserted into the bearing housing (not shown in Figure 4). The periphery 65 of the flange 64 is discontinuous. The periphery 65 of the flange 64 being discontinuous may be understood to mean that the periphery of the flange 64 is of non-constant radius. The periphery 65 of the flange 64 being discontinuous may be understood to mean that the periphery of the flange 64 is non-circular, but may define one or more arcuate sections. Each portion of the periphery 65 of the flange 64 may extend tangentially from the adjacent portions while the periphery of the flange 64 is discontinuous. The periphery 65 of the flange 64 defines a first flat portion 67 and a second flat portion 69. In some, non-depicted, embodiments, the periphery of the flange may define only a single flat portion, or may define three or more flat portions. The first flat portion 67 and the second flat portion 69 are disposed on diametrically opposed sides of the flange 64. However, this need not be the case. The flat portions 67, 69 define the at least one anti-rotation feature of the flange 64. In some embodiments, the periphery 65 of the flange 64 may define any discontinuous geometry. For example, the at least one anti-rotation feature of the flange 64 may be in the form of any other linear geometry, or one or more arcuate sections having a radius that differs to the radius of the major portion 71 of the flange. In use, the first arm 70 and the second arm 72, in particular the distal ends 77, 79 of the arms 70, 72, of the stop plate 28 are disposed adjacent to or engage the first flat portion 67 and the second flat portion 69 respectively to restrict rotation of the semi-floating ring bearing 26. The shape of the distal ends 77, 79 may be complementary to the geometry of the flat portions 67, 69, or to the geometry of any other anti-rotation defined by the flange 64. Therefore, the stop plate 28 and the flange 64 define a pair of complementary features that cooperate to restrict rotational movement of the semi-floating ring bearing 26. Referring now to Figure 5. As noted above, the bearing housing 8 comprises a groove 52. The groove 52 extends about the central axis (which extends into the page of Figure 5) of the turbocharger. The groove 52 extends circumferentially about the central axis of the turbocharger. The dashed line in Figure 5 shows the approximate location of the groove 52. The groove 52 is disposed in the first cavity 42. The groove 52 adjoins the first surface 48. The groove 52 is generally arcuate. However, in some embodiments, the groove 52 may take any suitable shape. For example, the groove 52 may be linear, and / or may define one or more vertices. The groove 52 is machined, for example milled, into the bearing housing 8. However, the groove 52 may be provided by any suitable method. At least part of the flange 64 is receivable by the groove 52, as will be discussed in more detail below. The groove 52 defines an arc angle. The arc angle of the groove 52 may be at least 10° and / or up to 170°. However, in some embodiments, the arc angle of the groove 52 may fall outside of this range. The arc angle of the groove 52 is greater than or equal to the arc angle of the major portion 71 of the flange 64. This advantageously reduces the likelihood of damage to the flange 64 during use when sustaining an axial load because the contact area between the flange 64 and the groove 52 is maximised. However, in some, nondepicted, embodiments, the arc angle of the groove 52 may be less than the arc angle of the major portion 71 of the flange 64. Preferably, the sum of the arc angle of the groove 52 and the arc angle of the major portion 71 of the flange 64 is less than 360°. The semi-floating ring bearing 26 may be placed in a first configuration and in a second configuration. The semi-floating ring bearing 26 is rotatable between the first configuration and the second configuration. In the first configuration, the semi-floating ring bearing 26 can be inserted into or withdrawn from the third cavity 46. In the first configuration of the semi-floating ring bearing 26, the minor portion 73 of the flange 64 is circumferentially aligned with the groove 52. That is to say, the major portion 71 of the flange 64 is not circumferentially aligned with the groove 52. This allows the semifloating ring bearing 26 to be inserted into the third cavity 46 such that the flange 64 engages the first surface 48 of the first cavity 42. Once the flange 64 is in engagement with the first surface 48, the semi-floating ring bearing 26 may be placed into the second configuration. Figure 5 shows the semi-floating ring bearing 26 in the second configuration. With the flange 64 in engagement with the first surface 48, rotation of the semi-floating ring bearing 26 about its central axis 56 moves the major portion 71 of the flange 64, into the groove 52. In the second configuration, the first and second flat portions 67, 69 of the flange 64 are not disposed in the groove 52. With the flange 64 in the groove 52, axial movement of the semi-floating ring bearing 26 is restricted by virtue of the engagement of the flange 64 with the groove 52. The flange 64 and the groove 52 therefore define a pair of complementary features that cooperate to restrict axial movement of the semi-floating ring bearing 26 in use. With the semi-floating ring bearing 26 in the second configuration, the arms of the stop plate (not shown in Figure 5) can be brought into engagement with respective flat portions 67, 69 of the flange 64 to restrict rotational movement of the semi-floating ring bearing 26. Assembly of the semi-floating ring bearing assembly 24 will now be discussed with reference to Figure 6. With the semi-floating ring bearing 26 in the first configuration, the semi-floating ring bearing 26, in particular the body 54 of the semi-floating ring bearing 26, is inserted into the third cavity 46 of the bearing housing 8 until the flange 64 engages the first surface 48 of the first cavity 42 of the bearing housing 8. The semi-floating ring bearing 26 is then rotated into the second configuration such that the major portion 71 of the flange 64 is received by the groove 52. The stop plate 28 is then inserted into the first cavity 42 of the bearing housing 8 such that the major portion 66 of the stop gate 28 engages the second surface 49 of the first cavity 42. In addition, the stop plate 28 is inserted such that the first and second arms (not visible in Figure 6) of the stop plate 28, in particular the distal ends of the arms, engage the first and second flat portions (not visible in Figure 6) respectively. Engagement of the arms with the flat portions restricts rotation of the semi-floating ring bearing 26. The first and second arms of the stop plate 28 and the first and second flat portions define complementary features that cooperate to restrict rotational movement of the semifloating ring bearing 26. The oil seal plate 36 is then inserted into the first cavity 42 such that it engages the stop plate 28. Engagement of the oil seal plate 36 with the stop plate 28 restricts movement of the stop plate 28. Figure 7 shows the bearing housing 8 following assembly of the semi-floating ring bearing assembly 24 into the bearing housing 8. As can be seen, the distal ends 77, 79 of the first and second arms 70, 72 are disposed adjacent to the flat portions 67, 69 of the flange 64. Furthermore, the flange 64 is disposed in the groove (not visible in Figure 7). Although the above description has been with reference to a turbocharger, the present invention is applicable to any type of turbomachine. For example, the present invention may be applied to an electric turbocharger, or a supercharger. While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

Claims

1. A semi-floating ring bearing assembly for a turbomachine, the semi-floating ring bearing assembly comprising:a bearing housing that comprises a bearing cavity;a stop plate; anda semi-floating ring bearing comprising:a body that comprises a central axis, a first end, a second end, and an external surface; anda flange that is disposed at the first end of the body;wherein the bearing housing and the flange define at least one pair of complementary features that cooperate to restrict axial movement of the semi-floating ring bearing, and wherein the stop plate and the flange define at least one pair of complementary features that cooperate to restrict rotational movement of the semifloating ring bearing.

2. The semi-floating ring bearing assembly of claim 1, wherein the bearing housing comprises a groove, and the flange is receivable by the groove to restrict axial movement of the semi-floating ring bearing.

3. The semi-floating ring bearing assembly of claim 2, wherein, in a first configuration of the semi-floating ring bearing, the semi-floating ring bearing can be inserted into or withdrawn from the bearing cavity, and in a second configuration of the semi-floating ring bearing, the flange of the semi-floating ring bearing is received by the groove such that axial movement of the semi-floating ring bearing is restricted.

4. The semi-floating ring bearing assembly of claim 3, wherein the semi-floating ring bearing is rotatable between the first configuration and the second configuration.

5. The semi-floating ring bearing assembly of any preceding claim, wherein a periphery of the flange is non-axisymmetric to define at least one anti-rotation feature that cooperates with at least one complementary anti-rotation feature of the stop plate.

6. The semi-floating ring bearing assembly of any preceding claim wherein, in aplane that is perpendicular to the central axis, the periphery of the flange is asymmetric.

7. The semi-floating ring bearing assembly of any preceding claim, wherein the periphery of the flange comprises at least one flat portion.

8. The semi-floating ring bearing assembly of claim 7, wherein the stop plate comprises at least one arm that is configured to engage the at least one anti-rotation feature of the flange to restrict rotation of the semi-floating ring bearing when the semifloating ring bearing is in the second configuration.

9. The semi-floating ring bearing assembly of any preceding claim, wherein the flange defines a major portion and a minor portion, the radius of the major portion being greater than the radius of the minor portion.

10. The semi-floating ring bearing assembly of claim 9, wherein an arc angle of the major portion is at least 30 degrees and less than 150 degrees.

11. The semi-floating ring bearing assembly of claim 2 and claim 9 or claim 10, wherein the groove defines an arc angle, and wherein the arc angle of the groove is greater than or equal to the arc angle of the major portion of the flange.

12. The semi-floating ring bearing assembly of any preceding claim, wherein the stop plate defines an oil baffle.

13. The semi-floating ring bearing assembly of any preceding claim, wherein a first axial end face of the body defines a thrust pad.

14. A semi-floating ring bearing for a turbomachine, the turbomachine comprising a bearing housing within which a stop plate is received, the semi-floating ring bearing comprising:a body that comprises a central axis, a first end, a second end, and an external surface; anda flange that is disposed at the first end of the body;wherein, when the semi-floating ring bearing is received by the bearing housing, the flange is configured to cooperate with the bearing housing to restrict axialmovement of the semi-floating ring bearing and to cooperate with the stop plate to restrict rotational movement of the semi-floating ring bearing.

15. The semi-floating ring bearing of claim 14, wherein a periphery of the flange is non-axisymmetric to define at least one anti-rotation feature that cooperates with at least one complementary anti-rotation feature of the stop plate.

16. The semi-floating ring bearing of claim 14 or claim 15, wherein, in a plane that is perpendicular to the central axis, the periphery of the flange is asymmetric.

17. The semi-floating ring bearing of claim of any of claims 14 to 16, wherein the periphery of the flange comprises at least one flat portion.

18. The semi-floating ring bearing of any of claims 14 to 17, wherein the flange defines a major portion and a minor portion, the radius of the major portion being greater than the radius of the minor portion.

19. The semi-floating ring bearing of claim 18, wherein an arc angle of the major portion is at least 30 degrees and less than 150 degrees.

20. The semi-floating ring bearing assembly of any of claims 14 to 19, wherein a first axial end face of the body defines a thrust pad.

21. A turbomachine comprising a semi-floating ring bearing assembly, the turbomachine comprising:a turbine and a compressor; anda semi-floating ring bearing assembly comprising:a bearing housing that is disposed between the turbine and the compressor, the bearing housing comprising a bearing cavity;a stop plate; anda semi-floating ring bearing comprising:a body that defines comprises a central axis, a first end, a second end, and an external surface; anda flange that is disposed at the first end of the body;wherein the bearing housing and the flange define at least one pair of complementary features that cooperate to restrict axial movement of the semi-floating ring bearing, and wherein the stop plate and the flange define at least one pair of complementary features that cooperate to restrict rotational movement of the semifloating ring bearing.

22. The turbomachine of claim 21, wherein the semi-floating ring bearing assembly is a semi-floating ring bearing assembly of any of claims 1 to 13.

23. A method of assembling a semi-floating ring bearing assembly for a turbomachine, the method comprising:providing a bearing housing that comprises a bearing cavity;providing a semi-floating ring bearing, the semi-floating ring bearing comprising:a body that comprises a central axis, a first end, a second end, and an external surface; anda flange that is disposed at the first end of the body;inserting the semi-floating ring bearing into the bearing housing; andmounting a stop plate to the bearing housing;wherein the bearing housing and the flange define at least one pair of complementary features that cooperate to restrict axial movement of the semi-floating ring bearing, and wherein the stop plate and the flange define at least one pair of complementary features that cooperate to restrict rotational movement of the semifloating ring bearing.

24. The method of claim 23, wherein the bearing housing comprises a groove, and wherein the method further comprises, subsequent to inserting the semi-floating ring bearing into the bearing cavity, rotating the semi-floating ring bearing such that the flange is disposed in the groove to restrict axial movement of the semi-floating ring bearing.

25. The method of claim 23 or claim 24, wherein the stop plate comprises at least one arm and the flange defines at least one anti-rotation feature, and wherein the stop plate is secured to the bearing housing such that the at least one arm of the stop plate engages the at least one anti-rotation feature to restrict rotation of the semi-floating ring bearing.

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