Bearing carrier

Abstract

Bearing carrier 2 supporting bearing 4 within a housing. The carrier has tubular body 12 to contain bearing 2, external flange 16 engaging the housing and internal lip 18 restricting axial movement of

Description

The present invention relates to a bearing carrier, a bearing carrier assembly and a method of assembling a shaft assembly, particularly to a bearing carrier, a bearing carrier assembly and a method of assembling a shaft assembly for use in a turbocharger or compressor, particularly an electric turbocharger or compressor. Bearings are used to support rotating shafts in many applications. In high RPM applications, such as turbomachinery where rotational speeds often exceed 100,000 RPM, bearings can be crucial to efficient and reliable operation of a device. The invention provides a bearing carrier for supporting a bearing within a housing, the bearing carrier extending along a carrier axis from a first end to a second end, the bearing carrier comprising: a tubular body to contain a bearing, the tubular body extending around and along the carrier axis; an external stop to engage a housing and limit movement of the bearing carrier relative to the housing along the carrier axis; an internal stop to engage an axial end of outer ring of a bearing and control movement of said bearing relative to the tubular body along the carrier axis; the tubular body comprising a deformable portion which is resiliently axially deformable to allow axial movement of the internal stop relative to the external stop to provide a bearing pre-load; and a bearing engaging portion adjacent the internal stop and comprising an inner engaging surface configured to engage an external circumferential wall of an outer ring of a bearing therein and an outer engaging surface to engage an inner wall of a housing, the bearing engaging portion being resiliently radially deformable to allow relative radial movement between the inner engaging surface and the outer engaging surface. The bearing carrier of the invention provides a deformable portion which is resiliently axially deformable and this allows the bearing carrier to be axially deformed during an assembly process and thereby provide a pre-load force to a bearing carried by the bearing. A pre-load force may be applied to a bearing to eliminate the internal clearance between the rolling elements and the rings. The axial deformation may be an elongation of the bearing carrier along the carrier axis. The bearing carrier of the invention also provides a bearing engaging portion which is resiliently radially deformable and may allow the bearing carrier to act as a bearing damper. A bearing damper is a device which can reduce the vibration and noise of a rotating shaft by providing a resiliently radially deformable component between the bearing and a housing in which the bearing and damper are installed. Resilient deformation of a component is characterised by the object returning to a pre-plastic-deformation state once the deforming force is removed and may be called elastic deformation. It should be noted that parts of the bearing carrier may, in addition to the resilient deformation, undergo a permanent, or plastic, deformation during installation. Plastic deformation of a component may mean that it cannot be re-used and must be replaced during a re-build. The bearing carrier is intended to carry a bearing and helps to arrange a bearing in a position relative to a housing. The bearing can be arranged in the tubular body against the internal stop to create a bearing carrier assembly. The bearing carrier assembly can then be arranged in a housing with the external stop against a wall of the housing and the deformable portion deformed by a pre-determined amount so that the bearing is arranged in a pre-determined location with respect to the housing and a pre-load force is applied to the bearing. The bearing may comprise an inner ring, an outer ring and rolling elements. The inner ring may be arranged within the outer ring and the rolling elements may be arranged between the inner and outer rings. The inner and outer rings may define a track within which the rolling elements are arranged to support rotation of the inner ring relative to the outer ring. The rolling elements may be substantially spherical, for example ball bearings. The bearing may comprise a bearing cage arranged between the inner and outer ring. The bearing cage may determine the position of the rolling elements, for example it may separate the rolling elements from one another. The bearing cage may maintain the rolling elements in an arrangement in which the rolling elements are spaced around the circumference substantially equally. The bearing carrier extends from a first end to a second end along a carrier axis and may take any suitable form. The bearing carrier comprises a tubular body which may take any suitable form. The tubular body may be substantially cylindrical in shape. The tubular body may comprise a body wall which extends around the carrier axis. The tubular body may comprise a plurality of components. The body wall of the tubular body may include features which may alter the mechanical properties of the tubular body. Such features may comprise cutouts which extend through the body wall, depressions or ridges in the surface of the body wall which may change the thickness of the wall, and deformations in the body wall which may, for example, give the wall a corrugated structure comprising a series of ridges and valleys. The features may extend axially for only a portion of the length of the tubular body, for example less than 50%, or less than 75% of the length. The features may extend axially for example at least 50%, at least 75%, or at least 90% of the length of the tubular body. The tubular body may extend from the first end of the bearing carrier, or may be spaced therefrom by a spacer or other component. The external stop may extend outward from any part of the tubular body, for example at or adjacent the first end of the bearing carrier, to engage a part of a housing in which the bearing carrier is to be installed. The external stop may extend circumferentially around and may extend radially away from the carrier axis. The external stop may extend substantially perpendicular to the carrier axis away from the tubular body. The external stop may be a substantially continuous circumferential wall or ridge. The external stop may comprise a plurality of circumferentially distributed external stop elements. There may be more than 6, more than 8, or more than 10 circumferentially distributed external stop elements. The external stop elements may be substantially equally distributed around the circumference. The internal stop may extend from any part of the tubular body, for example at or adjacent the second end of the bearing carrier, to engage a bearing installed within the tubular body. The internal stop may extend circumferentially around and may extend radially towards the carrier axis. The internal stop may extend substantially perpendicular to the carrier axis away from the tubular body. The internal stop may be a substantially continuous circumferential wall or ridge. The internal stop may comprise a plurality of circumferentially distributed internal stop elements. There may be more than 6, more than 8, or more than 10 circumferentially distributed internal stop elements. The internal stop elements may be substantially equally distributed around the circumference. The tubular body may extend from the second end of the bearing carrier. The internal stop may extend from the tubular body at or adjacent the second end of the bearing carrier and may extend circumferentially around and radially towards the carrier axis. The tubular body comprises a deformable portion which is resiliently axially deformable to allow axial movement of the internal stop relative to the external stop to provide a bearing pre-load. The deformable portion may comprise at least a portion of a circumferential wall which defines the tubular body such that axial deformation of the deformable portion causes the internal stop to move relative to the external stop which may alter the axial length of the bearing carrier. The deformable portion may comprise an element which carries the internal stop and can allow the internal stop to move relative to the external stop without changing the overall axial length of the bearing carrier. A part of the deformable portion may be resiliently stretched, or may be resiliently compressed, to provide the bearing pre-load. In use, a part of the deformable portion may be resiliently compressed, and another part may be resiliently stretched to provide the pre-load. The deformable portion may be deformable by at least 0.1mm, at least 0.2mm or at least 0.3mm. The deformable portion may be deformable by up to 1mm, up to 1.5mm, or up to 1.75mm, for example by stretching, to provide a bearing pre-load of between 5N and 200N, for example between 7N and 150N, or between 10N and 100N. This may allow a convenient, consistent pre-load force to be applied to the bearing during assembly and may take account of variations in dimensions due to manufacturing tolerances. The deformable portion may include features, for example weakened or removed portions, that facilitate the axial deformation of the deformable portion and determine the force required to cause the resilient deformation of the deformable portion, which may determine the pre-load force. The deformable portion of the tubular body may include axially and I or circumferentially offset apertures therethrough such that the deformable portion of the tubular body comprises a lattice structure. Altering the geometry of the aperture and the lattice may facilitate the creation of a suitable bearing pre-load force for an intended resilient deformation during installation. The deformable portion may comprise substantially the entire axial length of the tubular body, or may comprise a portion of said length, for example at least 50% or at least 70%. The bearing engaging portion is arranged adjacent the internal stop such that a bearing arranged in contact with the internal stop is arranged within the bearing engaging portion. The bearing engaging portion comprises an inner engaging surface to engage an external circumferential wall of an outer ring of a bearing. The outer engaging surface is to engage an inner wall of a housing. The bearing engaging portion is resiliently radially deformable to 5 allow relative radial movement between the inner engaging surface and the outer engaging surface as this may allow the bearing engaging portion to act as a bearing damper. The bearing engaging portion may include a bearing end support to radially support an end of a bearing arranged therein. The bearing end support may comprise a pair of bearing end support elements, with one bearing end support element at or adjacent each axial end of the bearing engaging portion. The bearing end support may radially support the bearing along substantially the full axial length of the bearing. The deformable portion of the tubular body may be separate from the bearing engaging portion. The deformable portion of the tubular body may include at least some of the bearing engaging portion. The bearing engaging portion of the tubular body may include a plurality of radial deformations which extend in the radial direction from or towards the carrier axis. The plurality of radial deformations may be substantially evenly distributed about the circumference of the tubular body. In this way, at least one of the inner engaging surface and the outer engaging surface comprises a discontinuity and will make intermittent contact with the outer surface of the bearing and / or housing. The radial deformations may be in any suitable form, for example projections such as raised hills or depressions such as dimples. The radial deformations may be in the form of axial ridges and / or valleys formed in a wall of the tubular housing which may result in a corrugated or wave-like wall structure. The radial deformations may extend over some, or all, of the bearing engaging portion and may extend over some, or all, of the bearing carrier. The radial deformations, for example the axial ridges and / or valleys, may extend from the first end to a second end of the bearing carrier and may be distributed substantially evenly around the circumference of the tubular body. These radial deformations may assist in altering the mechanical properties in the radial direction in the bearing engaging portion, it may make manufacturing and I or assembly easier if the deformations extend beyond the bearing engaging portion, for example it may make installing the bearing into the bearing carrier easier if there is a consistent internal surface design along the length of the tubular body. The radial deformations result in a variation in the radial distance of interior and or exterior of the tubular body from the carrier axis within the bearing engaging portion which may be at least 0.1mm, at least 0.2mm or at least 0.3mm. For example, the radial distance between the peaks and troughs in the corrugated structure may be at least 0.2mm. The material from which the bearing carrier is made may be any suitable material for the intended use scenario. The bearing carrier may be made from a metal, a plastic, a polymer, a laminate, or a fibre reinforced resin, or may be a combination of these. The bearing carrier may be formed by any suitable technique, or combination of techniques, including, for example, casting, moulding, pressing, machining, or additive manufacturing. The invention also provides a bearing carrier assembly comprising a bearing and a bearing carrier, the bearing carrier being as described above, and the bearing comprising an inner ring, an outer ring and rolling elements, the inner and outer rings defining a track within which the rolling elements are arranged to support rotation of the inner ring relative to the outer ring, the bearing located within the bearing carrier such that an axial end of the outer ring is in contact with the internal stop and an external circumferential wall of the outer ring is in contact with the inner engaging surface of the bearing engaging portion. The bearing may be as described above. It may comprise spherical rolling elements and may include a bearing cage to control the position of the rolling elements. The invention also extends to a method of creating a shaft assembly, the shaft assembly comprising a rotatable shaft, a bearing carrier assembly and a housing, the bearing carrier assembly being as described above and the housing including a wall with a cavity therein, the method comprising: arranging the rotatable shaft in the bearing such that a shoulder of the rotatable shaft is in contact with the inner ring of the bearing; arranging the tubular body of the bearing carrier within the cavity such that that the external stop is arranged against the wall and the outer engaging surface engages an inner wall of the cavity; applying a force along the rotatable shaft such that the deformable portion of the bearing carrier is axially deformed, and a preload force is applied across the bearing from the inner ring to the outer ring. The rotatable shaft may be any sort of rotatable shaft. The rotatable shaft may be intended, in use, to rotate at speeds of over 5000rpm, over 7500rpm, or over 10,000rpm. The rotatable shaft may be the shaft of an electric motor, compressor or turbocharger, for example the shaft of an electric compressor or turbocharger. The rotatable shaft may pass though the housing, or terminate at, or in, a wall of the housing. The housing may be, or may form part of, a mounting component, and provide structural support to locate the bearing carrier assembly and thereby rotatable shaft in a predetermined location. The bearing facilitates the rotation of the rotatable shaft relative to the housing. The invention will now be described by way of example only with reference to the following figures in which: Figure 1 shows an exploded cross section view of a bearing carrier assembly comprising a bearing carrier and a bearing; Figure 2 shows an end view of the bearing carrier of Figure 1; Figure 3 shows a cross section of a shaft assembly comprising the bearing carrier assembly of Figure 1; Figure 4 shows an end view of a second bearing carrier; Figure 5 shows a cross section through a bearing carrier assembly comprising the bearing carrier of Figure 4; Figure 6 shows an end view of a third bearing carrier; Figure 7 shows a bearing carrier assembly comprising the bearing carrier of Figure 6; and Figures 8, 9 and 10 show a perspective, cross section, and a perspective view of a bearing carrier. Figure 1 shows an exploded cross section view of a bearing carrier assembly 1 comprising a bearing carrier 2 and a bearing 4. The bearing carrier 2 is supporting a bearing 4 within a housing (best shown in Figure 3). The bearing carrier 2 extends along a carrier axis 6 from a first end 8 to a second end 10. The bearing carrier 2 comprises a tubular body 12 to contain the bearing 4. The tubular body 12 is substantially cylindrical in shape and extends around and along the carrier axis 6. The tubular body 12 comprises a circumferential wall 14 which extends from the first end 8 to a second end 10 of the bearing carrier 2. The bearing 4 comprises an outer ring 20, an inner ring 22 arranged substantially coaxially within the outer ring 20 and a plurality of rolling elements 24, in this case substantially spherical ball bearings, arranged between the inner and outer rings 20,22 to allow and 9 support rotation of outer ring 2 relative to the inner ring 22. A bearing cage 26 is provided to retain and distribute the rolling elements 24 between the outer and inner rings 20,22. There is an external stop 16 to engage a housing (not shown) and to limit movement of the bearing carrier 2 relative to the housing along the carrier axis 6. The external stop 16 extends substantially perpendicular to the carrier axis 6 from the first end 8 of the bearing carrier 2. An internal stop 18 is provided to engage an axial end 28 of the outer ring 20 of the bearing 4. The internal stop 18 is to control movement of the bearing 4 relative to the tubular body 12 along the carrier axis 6. When the bearing 4 is arranged against the internal stop 18, the bearing is prevented from moving along the carrier axis 6 beyond the internal stop 18. The internal stop 18 extends substantially perpendicular to the carrier axis 6 from the tubular body 12 at the second end of the bearing carrier 2. The tubular body 12 comprises a deformable portion 30 which is resiliently axially deformable along the carrier axis 6 to allow axial movement of the internal stop 18 relative to the external stop 16 to provide a bearing pre-load force. The tubular body 12 also comprises a bearing engaging portion 32 adjacent the internal stop 18. The bearing engaging portion 32 comprises an inner engaging surface 34 configured to engage an external circumferential wall 36 of an outer ring 20 of a bearing 4 therein. An outer engaging surface 38 is provided to engage an inner wall of a housing (shown in Figure 3). The bearing engaging portion 32 is resiliently radially deformable to allow relative radial movement between the inner engaging surface 34 and the outer engaging surface 38. Figure 2 shows an end view of the bearing carrier 2 of Figure 1. In this example the outer stop 16 is a continuous wall around the outside 42 of the tubular body 12 and the internal stop 18 is a continuous wall around the inside 44 of the tubular body 12, but the outer stop 16 and I or internal stop 18 may comprise a plurality of elements distributed about the circumference of the tubular body 12. To assemble the bearing carrier assembly 1, the bearing 4 is pressed into the tubular body 12 of bearing carrier 2 along the carrier axis 6 as indicted by arrows 40. The bearing 4 is pressed into the tubular body 12 until an axial end 28 of the outer ring 20 reaches the internal stop 18 at which location the bearing 4 is arranged within the bearing engaging portion 32. The bearing 4 is a press-fit, or friction-fit, within the bearing engaging portion 32 10 such that the outer circumferential wall 36 of the outer ring 20 of the bearing 4 is in contact with the inner engaging surface 34. This arrangement is shown in Figure 3. Figure 3 shows a cross section of a shaft assembly 46 comprising the bearing carrier assembly 1. The shaft assembly 46 comprises a rotatable shaft 48 which extends from a rotating device 50, for example an electric motor. The bearing carrier assembly 1 is inserted into cavity 52 in a wall 54 of a housing 56 such that the outside 42 of the bearing carrier 2, at least the outer engaging surface 38, is engaged with an inner surface 58 of the cavity 52. The cavity 52 of this example is a substantially cylindrical hole through the wall 54, but could be closed at one end. The tubular body 12 of the bearing carrier 2 is arranged within the cavity 52 such that that the external stop 16 is arranged against the wall 54 adjacent the cavity 52. A portion 62 of the rotatable shaft 48 is inserted into the inner ring 22 of the bearing 4 such that a shoulder 60 of the rotatable shaft 48 is in contact with the inner ring 22 of the bearing 4. During assembly, the rotatable shaft 48 is moved along the carrier axis 6 such that the deformable portion 30 of the bearing carrier 2 is axially deformed. To deform the deformable portion 30 a force is applied along the rotatable shaft 48 and that force is transferred to the inner ring of the 22 and then to the outer ring 20 via the rotating elements 24. The outer ring 20 of the bearing 4 is arranged against the internal stop 18 of the bearing carrier 2 and the force from the rotatable shaft 48 is transferred to the internal stop 18 of the bearing carrier 2. Movement of the rotatable shaft 48 into the bearing carrier 2 causes the deformable portion 30 of the bearing carrier 2 to be resiliently axially deformed, or stretched. The first end 8 of the bearing carrier 2 is prevented from moving into the cavity 52 by the external stop 16 and the rotatable shaft 48 is applying a force to the internal stop 18. The resilient deformation of the deformable portion 30 results in a preload force is applied across the bearing between the inner ring 22 and the outer ring 20. The preload force applied to the bearing 4 ensures that the rotating elements 24 are in contact with the inner and outer rings 20,22 of the bearing 4. Figure 4 shows an end view of a bearing carrier 102. In this example the outer stop 116 comprises a plurality of outer stop elements 66, in this example the outer stop elements 66 are substantially triangular, but may be other shapes. The outer stop elements 66 are distributed evenly around the outside 142 of the tubular body 112. The internal stop 118 is a continuous wall around the inside 144 of the tubular body 112. The tubular body 112 comprises a wall 114 which is deformed into a zig-zag corrugation comprising a plurality of radially outwardly directed triangular peaks 68 and radially inwardly directed triangular troughs 70 forming axial ridges and valleys along the tubular body 112. In this example, an outer stop element 66 extends from each of the radially directed triangular peaks 68. The ridges and valleys are substantially evenly distributer around the tubular body 112. Figure 5 shows a cross section through a bearing carrier assembly 101 comprising the bearing carrier 102 of Figure 4. The tubular body 112 comprises a plurality of axially and circumferentially offset cutouts or apertures 72 which extend though the tubular wall 114 such that the deformable portion 130 of the tubular body 112 comprises a lattice structure. In this example, when the deformable portion 130 is not deformed the apertures 72 are rectangular in shape so that legs 74 which form the lattice structure are substantially straight. The dimensions, geometry and material of the lattice structure contribute to the resilient axial deformability of the deformable portion 130. In this example the deformable portion does not extend along the entire length of the tubular body 112 and the bearing engaging portion 132 is axially spaced apart from the deformable portion 130. By adjusting these features, the pre-load force provided to a bearing in a shaft assembly can be adjusted. Figures 6 and 7 show views similar to those shown in Figures 4 and 5, but showing a bearing carrier 202. In this example the outer stop 216 comprises a plurality of outer stop elements 266, in this example the outer stop elements 266 are a rounded substantially triangular shape. The outer stop elements 266 are distributed evenly around the tubular body 212. The internal stop 218 comprises a plurality of internal stop elements 76, in this example the internal stop elements 76 are a rounded substantially triangular shape. The tubular body 212 comprises a wall 214 which is deformed into a curved corrugation, or wave-like structure, comprising a plurality of radially outwardly directed peaks 268 and radially inwardly directed troughs 270 forming axial ridges and valleys along the tubular body 212. In this example, an outer stop element 266 extends from each of the radially directed peaks 268 and an internal stop element 76 extends inwardly from each of the radially directed troughs 270. The tubular body 212 comprises a plurality of axially and circumferentially offset cutouts or apertures 272 which extend though the tubular wall 214 such that the deformable portion 230 of the tubular body 212 comprises a lattice structure. In this example, when the deformable portion 230 is not deformed the apertures 272 are shaped so that the legs 274 extend at circumferentially and axially. Figures 8, 9 and 10 show a perspective, cross section and a perspective view of a bearing carrier 302. The bearing carrier 302 is similar in structure to the bearing carrier 202 with an axially corrugated tubular body 312 comprising a plurality of internal stop elements 376 and a plurality of outer stop elements 366 extending therefrom. A plurality of axially and circumferentially apertures 372 extend through the tubular body 312. In this example it can be seen that the deformable portion 330 of the tubular body 312 comprises substantially all of the tubular body 312 and that the radial deformations, in this case the axially extending ridges 368 and valleys 370 that define a corrugated structure around the circumference of the tubular body 312, extend for substantially the entire length of the tubular body 312.

Claims

1. A bearing carrier for supporting a bearing within a housing, the bearing carrier extending along a carrier axis from a first end to a second end, the bearing carrier comprising:a tubular body to contain a bearing, the tubular body extending around and along the carrier axis;an external stop to engage a housing and limit movement of the bearing carrier relative to the housing along the carrier axis;an internal stop to engage an axial end of outer ring of a bearing and control movement of said bearing relative to the tubular body along the carrier axis;the tubular body comprising a deformable portion which is resiliently axially deformable to allow axial movement of the internal stop relative to the external stop to provide a bearing pre-load; anda bearing engaging portion adjacent the internal stop and comprising an inner engaging surface configured to engage an external circumferential wall of an outer ring of a bearing therein and an outer engaging surface to engage an inner wall of a housing, the bearing engaging portion being resiliently radially deformable to allow relative radial movement between the inner engaging surface and the outer engaging surface.

2. A bearing carrier as claimed in claim 1, in which the tubular body extends from the first end of the bearing carrier, and the external stop extends from the tubular body at or adjacent the first end of the bearing carrier and extends circumferentially around and radially away from the carrier axis.

3. A bearing carrier as claimed in claim 2, in which the external stop comprises a plurality of circumferentially distributed external stop elements.

4. A bearing carrier as claimed in any preceding claim, in which the tubular body extends from the second end of the bearing carrier, and the internal stop extends from the tubular body at or adjacent the second end of the bearing carrier and extends circumferentially around and radially towards the carrier axis.

5. A bearing carrier as claimed in claim 4, in which the internal stop comprises a plurality of circumferentially distributed internal stop elements.

6. A bearing carrier as claimed in any preceding claim, in which the deformable portion of the tubular body includes axially and circumferentially offset apertures therethrough such that the deformable portion of the tubular body comprises a lattice structure.

7. A bearing carrier as claimed in any preceding claim, in which the external stop comprises a plurality of circumferentially distributed external stop elements.

8. A bearing carrier as claimed in any preceding claim, in which the deformable portion of the tubular body includes at least some of the bearing engaging portion.

9. A bearing carrier as claimed in any preceding claim, in which the bearing engaging portion of the tubular body includes a plurality of radial deformations such that at least one of the inner engaging surface and outer engaging surface comprise a plurality discontinuities therein.

10. A bearing carrier as claimed in claim 9, in which the radial deformations are in the form of axial ridges formed in a wall of the tubular housing.

11. A bearing carrier as claimed in claim 10, in which the axial ridges extend from the first end to a second end of the bearing carrier.

12. A bearing carrier as claimed in any preceding claim, in which the material from which the bearing carrier is made comprises a polymer material.

13. A bearing carrier as claimed in any preceding claim, in which the deformable portion provides a pre-load force of between 5N and 200N with an axial deformation of between 0.1 and 1.75mm.

14. A bearing carrier assembly comprising a bearing and a bearing carrier, the bearing carrier being as claimed in any preceding claim, and the bearing comprising an inner ring, an outer ring and rolling elements, the inner and outer rings defining a track within which the rolling elements are arranged to support rotation of the inner ring relative to the outer ring, the bearing located within the bearing carrier such that an axial end of the outer ring is in contact with the internal stop and an external circumferential wall of the outer ring is in contact with the inner engaging surface of the bearing engaging portion.

15. A method of creating a shaft assembly, the shaft assembly comprising a rotatable shaft, a bearing carrier assembly and a housing, the bearing carrier assembly being as claimed in claim 14 and the housing including a wall with a cavity therein, the method comprising:5 arranging the rotatable shaft in the bearing such that a shoulder of the rotatable shaftis in contact with the inner ring of the bearing;arranging the tubular body of the bearing carrier within the cavity such that that the external stop is arranged against the wall and the outer engaging surface engages an inner wall of the cavity;10 applying a force along the rotatable shaft such that the deformable portion of thebearing carrier is axially deformed, and a preload force is applied across the bearing from the inner ring to the outer ring.15

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