Bearing assembly for supporting the rotation of a shaft in a turbocharger

Abstract

Bearing assembly (34) for supporting the rotation of a shaft (12) in a turbocharger (10), wherein the bearing assembly (34) comprises the following: an inner ring (36, 106, 108) extending along an axis (A) and configured to be coupled to the shaft (12), a first outer ring (88) which is radially spaced from the inner ring (36, 106, 108), a first cage (90) arranged radially between the inner ring (36, 106, 108) and the first outer ring (88), and a first rolling element (92) which is arranged radially between the first outer ring (88) and the inner ring (36, 106, 108) and is arranged within the first cage (90) to assist the rotation of the shaft (12), a second outer ring (96) which is spaced apart from the first outer ring (88) along the axis (A) and radially spaced from the inner ring (36, 106, 108), a second cage (98) arranged radially between the inner ring (36, 106, 108) and the second outer ring (96), a second rolling element (100) which is arranged radially between the second outer ring (96) and the inner ring (36, 106, 108) and is arranged inside the second cage (98) to assist the rotation of the shaft (12), characterized in that the first outer ring (88) defines a primary lubricant passage (74) configured to direct lubricant towards the first cage (90), and that the first outer ring (88) defines a secondary lubricant passage (76), which is spaced apart from the primary lubricant passage (74) along the axis (A).

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The invention generally relates to a turbocharger, including a bearing assembly. 2. Description of the state of the art

[0002] Turbochargers take exhaust gas from an internal combustion engine and deliver pressurized air to the internal combustion engine. Turbochargers are used to increase the power output of the internal combustion engine, reduce the fuel consumption of the internal combustion engine, and reduce emissions produced by the internal combustion engine. The delivery of pressurized air to the internal combustion engine by the turbocharger allows the internal combustion engine to be smaller, yet capable of developing the same or a similar amount of horsepower as larger naturally aspirated internal combustion engines. Having a smaller internal combustion engine for use with a vehicle reduces the mass and aerodynamic frontal area of ​​the vehicle, which helps to reduce the fuel consumption of the internal combustion engine and improve the vehicle's fuel economy.

[0003] Typical turbochargers include a turbine housing defining a turbine housing interior, a turbine wheel disposed within the turbine housing interior for receiving exhaust gas from the internal combustion engine, and a shaft coupled to and rotatable thereby. Typical turbochargers also include a compressor housing defining a compressor housing interior, and a compressor wheel disposed within the compressor housing interior and coupled to the shaft. The compressor wheel is rotatable by the shaft to deliver compressed air to the internal combustion engine. Specifically, energy from the exhaust gas from the internal combustion engine, which would normally be wasted, is used to rotatably drive the turbine wheel, which is used to rotatably drive the shaft and, in turn, rotatably drive the compressor wheel to compress air and deliver compressed air to the internal combustion engine.

[0004] Turbochargers generally include a bearing assembly arranged around the shaft. Bearing assemblies are known to support shaft rotation. CN 111 648 983A discloses a turbocharger with a ball bearing. The ball bearing comprises an outer ring with oil inlet holes. WO 2017 / 095 690 A1 relates to an asymmetric ball bearing system for a turbocharger. DE 10 2012 206 556 A1 describes a bearing arrangement for a turbocharger. Further reference is made to: BÖGE, Gert; BÖGE, Wolfgang: Roller Bearings, in: BÖGE, Alfred (ed.), et al.: Handbook of Mechanical Engineering. Fundamentals and Applications of Mechanical Engineering Technology. 23rd, revised edition, Wiesbaden: Springer, 2017. pp. 884–908, ISBN 978-3-658-12529-5, DOI: 10.1007 / 978-3-658-12529-5. Reference is also made to POLL, G.: Rolling Bearings, in: GROTE, Karl-Heinrich (ed.), et al.: Dubbel, Handbook for Mechanical Engineering. 25th, revised and updated edition, Berlin: Springer, 2019. pp.G80-G95, ISBN 978-3-662-54805-9, DOI: 10.1007 / 978-3-662-54805-9. Further bearing arrangements are specified in DIN 611 2010-05-00 Rolling bearings. WO 2016 / 086 933 A1, DE 90 17 861 U1, DE 10 2014 215 739 B4, DE 10 2016 222 415 B4 and DE 10 2018 201 827 A1. Furthermore, the bearing assemblies known in the art typically include various components that require lubrication with a lubricant. However, bearing assemblies known in the art may fail due to an inadequate supply of lubricant to the various components of the bearing assemblies. More specifically, an inadequate supply of lubricant to the various components of the bearing assemblies may lead to the degradation of the small amount of lubricant present on the various components of the bearing assemblies due to increased heat generated by friction between various components of the bearing assemblies during operation of the turbocharger.Furthermore, repeated wear on various components of the bearing assemblies can be due to inadequate lubrication. Repeated wear on various components of the bearing assemblies can also increase turbocharger noise, vibration, and harshness (NVH). Repeated wear on various components of the bearing assemblies can also lead to failure of the bearing assemblies to support shaft rotation. Failure of the bearing assemblies to support shaft rotation will damage the turbocharger.

[0005] Therefore, there remains a need for an improved bearing assembly for a turbocharger, and in particular one that enables improved lubricant delivery. SUMMARY OF THE INVENTION AND ADVANTAGES

[0006] The present object is achieved by a bearing assembly for supporting the rotation of a shaft in a turbocharger according to claim 1, as well as a turbocharger for delivering compressed air to an internal combustion engine with such a bearing assembly according to claim 11. The dependent claims define preferred embodiments of the bearing assembly. The bearing assembly for supporting the rotation of a shaft in a turbocharger includes an inner ring configured to be coupled to the shaft, a first outer ring radially spaced from the inner ring, and a first cage radially disposed between the inner ring and the first outer ring. The bearing assembly also includes a first rolling element radially disposed between the first outer ring and the inner ring. The first rolling element is disposed within the first cage to support the rotation of the shaft.The bearing assembly further includes a second outer ring spaced from the first outer ring along the axis and radially spaced from the inner ring, a second cage radially disposed between the inner ring and the second outer ring, and a second rolling element radially disposed between the second outer ring and the inner ring and disposed within the second cage to assist in rotation of the shaft. The first outer ring defines a primary lubricant passage configured to direct lubricant toward the first cage. The first outer ring defines a secondary lubricant passage spaced from the primary lubricant passage along the axis.

[0007] Because the lubricant passage is configured to direct lubricant toward the cage, the cage is adequately lubricated with the lubricant. Adequate lubrication of the cage with the lubricant prevents failure of the bearing assembly. Specifically, the lubricant reduces friction between the rolling element, outer ring, inner ring, and cage, and also limits degradation of the lubricant surrounding the cage, which would result from heat generated by friction between the rolling element, outer ring, inner ring, and cage during turbocharger operation.Since the lubricant passage is configured to direct lubricant toward the cage, the rolling element, outer ring, inner ring, and cage are also provided with cooling resulting from an increased amount of lubricant surrounding the cage, which further prevents degradation of the lubricant as well as heat that may result from friction between the rolling element, outer ring, inner ring, and cage during operation of the turbocharger.

[0008] Furthermore, wear on the rolling element, outer ring, inner ring, and cage is limited because the cage is adequately lubricated with the lubricant supplied to the cage through the lubricant passage. Since wear on the rolling element, outer ring, inner ring, and cage is limited, noise, vibration, and harshness (NVH) of the turbocharger is also limited. Functional failure of the bearing assembly supporting shaft rotation is also prevented because wear on the rolling element, outer ring, inner ring, and cage is limited. This prevents damage to the turbocharger. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which: Fig. 1 is a schematic representation of a turbocharger including a shaft extending along an axis, a compressor wheel coupled to the shaft, and a turbine wheel coupled to the shaft, Fig. 2 a cross-sectional view of the turbocharger of Fig. 1, wherein the turbocharger includes a bearing assembly for supporting the rotation of the shaft, and wherein the bearing assembly includes an inner ring, a first outer ring, a second outer ring, a first cage, a second cage, a first rolling element, a second rolling element, a first biasing element, and a second biasing element, Fig. 3A is a cross-sectional view of the first outer ring, the first cage, the first rolling element and the inner ring, and Fig. 3B is a cross-sectional view of the second outer ring, the second cage, the second rolling element and the inner ring. DETAILED DESCRIPTION OF THE INVENTION

[0010] Referring to the figures, wherein like numerals indicate like parts throughout the several views, a turbocharger 10 for delivering pressurized air to an internal combustion engine includes a shaft 12 extending along an axis A between a first shaft portion 14 and a second shaft portion 16 spaced from the first shaft portion 14 along the axis A. The turbocharger 10 includes a compressor wheel 18 coupled to the first shaft portion 14 of the shaft 12 and a turbine wheel 20 coupled to the second shaft portion 16 of the shaft 12. The turbocharger 10 may include a compressor housing 22 defining a compressor housing interior 24 in which the compressor wheel 18 is disposed, and a turbine housing 26 defining a turbine housing interior 28 in which the turbine wheel 20 is disposed. The turbocharger may also include a bearing housing 30 defining a bearing housing interior 32.The turbocharger 10 also includes a bearing assembly 34 to support the rotation of the shaft 12. The bearing assembly 34 may be arranged in the bearing housing interior 32.

[0011] The bearing assembly 34 includes an inner ring 36 coupled to the shaft 12, an outer ring 38 radially spaced from the inner ring 36, and a cage 40 radially disposed between the inner ring 36 and the outer ring 38. The bearing assembly 34 also includes a rolling element 42 radially disposed between the outer ring 38 and the inner ring 36. The rolling element 42 is disposed within the cage 40 to assist in the rotation of the shaft 12. The outer ring 38 defines a lubricant passage 44 configured to direct lubricant toward the cage 40.

[0012] Because the lubricant passage 44 is configured to direct lubricant toward the cage 40, the cage 40 is adequately lubricated with the lubricant. Adequate lubrication of the cage 40 with the lubricant prevents failure of the bearing assembly 34. More specifically, the lubricant reduces friction between the rolling element 42, the outer ring 38, the inner ring 36, and the cage 40, thus limiting degradation of the lubricant surrounding the cage 40, which would result from heat generated by friction between the rolling element 42, the outer ring 38, the inner ring 36, and the cage 40 during operation of the turbocharger 10.Thus, since the lubricant passage 44 is configured to direct lubricant toward the cage 40, the rolling element 42, the outer ring 38, the inner ring 36, and the cage 40 are also provided with cooling resulting from an increased amount of lubricant surrounding the cage 40, which further prevents degradation of the lubricant, as well as heat that may result from friction between the rolling element 42, the outer ring 38, the inner ring 36, and the cage 40 during operation of the turbocharger 10.

[0013] Furthermore, wear on the rolling element 42, outer ring 38, inner ring 36, and cage 40 is limited because the cage 40 is adequately lubricated with the lubricant supplied to the cage 40 through the lubricant passage 44. Since wear on the rolling element 42, outer ring 38, inner ring 36, and cage 40 is limited, the noise, vibration, and harshness (NVH) of the turbocharger 10 is also limited. Failure of the bearing assembly 34 to support the rotation of the shaft 12 is also prevented because wear on the rolling element 42, outer ring 38, inner ring 36, and cage 40 is limited. Thus, damage to the turbocharger 10 is also prevented.

[0014] The turbocharger 10 may further include an electric machine 46, such as an electric motor and / or an electric generator, disposed about the shaft 12. The electric machine 46 may be disposed within the bearing housing interior 32 of the bearing housing 30. The electric machine 46 may include a rotor 48 coupled to the shaft 12 and configured to rotate with the shaft, a stator 50 radially spaced from the rotor 48 and including a plurality of windings that can be energized to impart rotational energy to the rotor 48, and thus to the shaft 12. The electric machine 46 may assist the turbocharger 10 in delivering pressurized air to the internal combustion engine by increasing the speed of the shaft 12 when the exhaust gas from the internal combustion engine is insufficient in transferring rotational energy to the turbine wheel 20.

[0015] Although not required, the cage 40 may have an inner cage surface 52 facing the rolling element 42, and the inner cage surface 52 of the cage 40 defines a cage interior 54. As discussed above, the rolling element 42 may be disposed within the cage 40. More specifically, the rolling element 42 may be disposed within the cage interior 54 defined by the inner cage surface 52 of the cage 40. It should be understood that the rolling element 42 need not be entirely disposed within the cage 40, and the rolling element 42 need not be entirely disposed within the cage interior 54 defined by the inner cage surface 52 of the cage 40. Instead, the rolling element 42 need only be partially surrounded by the cage 40 to be within the cage 40.Additionally, the cage 40 may include a coating or surface treatment applied to harden the cage 40 and further reduce wear on the cage 40. The rolling element 42 of the bearing assembly 34 may be a ball bearing. However, it should be understood that the rolling element 42 may have any number of geometric shapes, including cylindrical, and may be bushings or roller bearings.

[0016] The cage 40 may extend from a first cage end 56 at a first location 58 along axis A to a second cage end 60 at a second location 62 along axis A, different from the first location 58. A distance (D) may be defined between the first location 58 along axis A and the second location 62 along axis A.

[0017] Although not required, the lubricant passage 44 may be located within a lubricant boundary (LB) defined as between 25% of the distance D from the first location 58 along axis A and 25% of the distance from the second location 62 along axis A. In other words, the lubricant passage 44 may be located within 25% of the distance D from the first location 58 and / or the lubricant passage 44 may be located within 25% of the distance D from the second location 62 along axis A.It should be understood that the lubricant passage 44 may be located within 20% of the distance D from one of the first location 58 along axis A and the second location 62 along axis A, within 15% of the distance D from one of the first location 58 along axis A and the second location 62 along axis A, within 10% of the distance from one of the first location 58 along axis A and the second location 62 along axis A, and / or within 5% of the distance from one of the first location 58 along axis A and the second location 62 along axis A.It should also be understood that in embodiments where the lubricant passage 44 is located within 20%, 15%, 10%, and / or 5% of the distance D from one of the first location 58 along axis A and the second location 62 along axis A, the lubricant passage 44 may still be located between the first location 58 along axis A and the second location 62 along axis A. In other words, the lubricant passage 44 being within 20%, 15%, 10%, and / or 5% of the distance D from the first location 58 along axis A and the second location 62 along axis A defines the lubricant boundary LB for the lubricant passage 44 as an outermost boundary and does not preclude the lubricant passage 44 from being defined equidistant between the first location 58 along axis A and the second location 62 along axis A, in one non-limiting example.

[0018] The outer ring 38 may have an inner surface 64 facing the inner ring 36. The outer ring may also have an outer surface 66 facing away from the inner ring 36. The outer ring 38 may also have a radial surface 68 defined extending radially away from the axis A1. The inner surface 64 of the outer ring 38 may define an outlet 70 in fluid communication with the lubricant passage 44. The outer surface 66 of the outer ring 38 may also define an inlet 72 in fluid communication with the lubricant passage 44. However, it should also be understood that the radial surface 68 may define the inlet 72 in fluid communication with the lubricant passage 44. Lubricant may flow through the outer ring 38 by entering the inlet 72, flowing through the lubricant passage 44, and dispensing from the outlet 70. The outlet 70 may be configured to direct the lubricant toward the cage 40 of the bearing assembly 34.It is understood that the inlet 72 may be defined as a groove extending at least partially about the axis A. Alternatively, it is understood that the inlet 72 may be defined as a counterbore.

[0019] In one embodiment, at least a portion of the lubricant passage 44 is located between the first location 58 along axis A and the second location 62 along axis A. In other words, the entire lubricant passage 44 need not be located between the first location 58 along axis A and the second location 62 along axis A. In one non-limiting example, the inlet 72 and the outlet 70 may be located outside of the first location 58 along axis A and the second location 62 along axis A, however, the portion of the lubricant passage 44 may nonetheless be located between the first location 58 along axis A and the second location 62 along axis A.

[0020] Although not required, at least a portion of the outlet 70 may be located between the first location 58 along axis A and the second location 62 along axis A. In other words, a portion of the outlet 70 may be located outside of between the first location 58 along axis A and the second location 62 along axis A, and the portion of the outlet 70 may be located between the first location 58 along axis A and the second location 62 along axis A. Because the portion of the outlet 70 is located between the first location 58 along axis A and the second location 62 along axis A, the lubricant passage 44 is assisted in directing lubricant toward the cage 40.It is also to be understood that the entire outlet 70 may be located between the first location 58 along axis A and the second location 62 along axis A, further assisting the lubricant passage 44 in directing lubricant toward the cage 40.

[0021] Furthermore, at least a portion of the inlet 72 may be located between the first location 58 along axis A and the second location 62 along axis A. In other words, a portion of the inlet 72 may be located outside of between the first location 58 along axis A and the second location 62 along axis A, and the portion of the inlet 72 may be located between the first location 58 along axis A and the second location 62 along axis A. Because the portion of the inlet 72 is located between the first location 58 along axis A and the second location 62 along axis A, the lubricant passage 44 is assisted in directing lubricant toward the cage 40.It is also to be understood that the entire inlet 72 may be located between the first location 58 along axis A and the second location 62 along axis A, further assisting the lubricant passage 44 in directing lubricant toward the cage 40.

[0022] Although not required, it should be understood that the entire inlet 72 can be located between the first location 58 along axis A and the second location 62 along axis A, the entire lubricant passage 44 can be located between the first location 58 along axis A and the second location 62 along axis A, and the entire outlet 70 can be located between the first location 58 along axis A and the second location 62 along axis A. Further, it should be understood that the lubricant passage 44 can be defined radially through the outer ring 38 perpendicular to axis A. In other words, the inlet 72 and the outlet 70 can be defined at the same location along axis A, and the lubricant passage 44 can be defined as a straight passage immediately between the inlet 72 and the outlet 70.

[0023] The inlet 72 may have an axial width of between about 0.1 and about 2 millimeters, between about 0.2 and about 1.8 millimeters, between about 0.3 and about 1.6 millimeters, between about 0.4 and about 1.4 millimeters, between about 0.5 and about 1.2 millimeters, between about 0.6 and about 1 millimeter, and about 0.8 millimeters. Furthermore, the outlet 70 may have an axial width of between about 0.1 and about 2 millimeters, between about 0.2 and about 1.8 millimeters, between about 0.3 and about 1.6 millimeters, between about 0.4 and about 1.4 millimeters, between about 0.5 and about 1.2 millimeters, between about 0.6 and about 1 millimeter, and about 0.8 millimeters. In addition, although not required, the lubricant passage 44 may be further defined as a lubricant jet. Furthermore, the lubricant passage 44 may have a nozzle configuration.

[0024] The lubricant passage 44 is defined as a primary lubricant passage 74, and the outer ring 38 defines a secondary lubricant passage 76. The secondary lubricant passage 76 is spaced from the primary lubricant passage 74 along the axis A. The secondary lubricant passage 76 need not be configured to direct lubricant toward the cage 40; however, it should be understood that the secondary lubricant passage 76 may be configured to direct lubricant toward the cage 40 and may optionally selectively include any combination of features of the primary lubricant passage 74 as described herein. The secondary lubricant passage 76 may assist in providing lubricant to components of the bearing assembly 34 other than or in addition to the cage 40.

[0025] The bearing assembly 34 may further include a squeeze film damper cup 78 that is rotationally fixed relative to the outer ring 38 such that the outer ring 38 is radially disposed between the squeeze film damper cup 78 and the inner ring 36. It should be understood that the squeeze film damper cup 78 and the outer ring 38 may be formed integrally with each other. Alternatively, the squeeze film damper cup 78 and the outer ring 38 may be separate components. In embodiments where the squeeze film damper cup 78 is a separate component from the outer ring 38, the outer ring 38 may be press-fitted into the squeeze film damper cup 78 or otherwise physically attached thereto. In embodiments with the squeeze film damper cup 78, the lubricant passage 44 may be defined by the squeeze film damper cup 78. The squeeze film damper pot 78 may also define the inlet 72 and may also define the outlet 70.

[0026] The cage 40 of the bearing assembly 34 may have an outer cage surface 80 facing the inner surface 64 of the outer ring 38. The outlet 70 may be configured to direct lubricant toward the outer cage surface 80 of the cage 40. It should be understood that the outlet 70 may be aligned with the outer cage surface 80 of the cage 40.

[0027] Furthermore, the cage 40 of the bearing assembly 34 may have a first outer portion 82 adjacent the first cage end 56. The first outer portion 82 of the cage 40 has a first radial height RH1. The cage 40 of the bearing assembly 34 may also have a second outer portion 84 adjacent the second cage end 60. The second outer portion 84 of the cage 40 has the first radial height RH1. In other words, the first outer portion 82 of the cage 40 and the second outer portion 84 of the cage 40 have the same radial height. The cage 40 of the bearing assembly 34 may further have a middle portion 86 axially disposed between the first outer portion 82 and the second outer portion 84. The central portion 86 of the cage 40 has a second radial height RH2 that differs from the first radial height RH2 of the first outer portion 82 and the second outer portion 84.More specifically, the second radial height RH2 of the central portion 86 may be less than the first radial height RH1 of the first outer portion 82 and the second outer portion 84. It should be understood that the first radial height RH1 and the second radial height RH2 do not refer to relative distances from the axis A, but rather are relative lengths of the components themselves. Therefore, the first radial height RH1 and the second radial height RH2 may extend to the same radial distance from the shaft 12.

[0028] Although not required, the outlet 70 may further be aligned with the first outer portion 82 of the cage 40 or the second outer portion 84 of the cage 40. The outlet 70 may be configured to direct lubricant to the first outer portion 82 of the cage 40 and / or the second outer portion 84 of the cage 40.

[0029] In addition, as in Fig. 3A and Fig. 3B, the outer cage surface 80 at the first outer portion 82 may extend a first radial distance RD1 from the axis A, and the outer cage surface 80 at the second outer portion 84 may extend the first radial distance RD1 from the axis A. The outer cage surface 80 at the central portion 86 may extend a second radial distance RD2 from the axis A. The second radial distance RD2 may be less than the first radial distance RD1. Therefore, in this embodiment, the outer cage surface 80 of the cage 40 defines an indentation that forms a gap between the central portion 86 of the cage 40 and the outer ring 38 of the bearing assembly 34.However, it should be understood alternatively that the outer cage surface 80 at the first outer portion 82, the second outer portion 84, and the central portion 86 may all extend the first radial distance from the axis A, while the first outer portion 82 and the second outer portion 84 have the first radial height RH1 and the central portion 86 has the second radial height RH2.

[0030] The outer ring 38 is defined as a first outer ring 88, the cage 40 is defined as a first cage 90, the rolling element 42 is defined as a first rolling element 92, and the primary lubricant passage 74 may further be defined as a first primary lubricant passage 94, as in Fig. 2 and Fig. 3A. As shown in Fig. 2 and Fig.3B, the bearing assembly 34 further includes a second outer ring 96 spaced from the first outer ring 88 along axis A and radially spaced from the inner ring 36. The bearing assembly 34 also includes a second cage 98 radially disposed between the inner ring 36 and the second outer ring 96. The bearing assembly 34 also includes a second rolling element 100 radially disposed between the second outer ring 96 and the inner ring 36. The second rolling element 100 is disposed within the second cage 98 to assist in rotation of the shaft 12. The second outer ring 96 can define a second primary lubricant passage 102 through the second outer ring 96. The second primary lubricant passage 102 is configured to direct lubricant toward the second cage 98. The second primary lubricant passage 102 provides the advantages of the first primary lubricant passage 94 as described above.The second primary lubricant passage 102 may optionally selectively include any combination of features of the first primary lubricant passage 94, as described above. Furthermore, the second outer ring 96, the second cage 98, and the second rolling element 100 may optionally selectively include any combination of features of the first outer ring 88, the first cage 90, and the first rolling element 92, as described herein. For example, in one non-limiting example, the second outer ring 96 may be rotationally fixed relative to a second squeeze film damper cup 104 such that the second outer ring 96 is radially disposed between the second squeeze film damper cup 104 and the inner ring 36.

[0031] The inner ring 36 of the bearing assembly 34 can have numerous designs. In one embodiment, the inner ring 36 is a unitary component. In other words, the inner ring 36 can extend approximately between the first and second shaft portions 14, 16 of the shaft 12 such that the inner ring 36 is a single piece between the first and second rolling elements 92, 100.

[0032] Alternatively, the inner ring 36 may include a first inner ring 106 disposed between the first outer ring 88 and the shaft 12, and may include a second inner ring 108 disposed between the second outer ring 96 and the shaft 12. In the embodiments having the first and second inner rings 106, 108, the first inner ring 106 and the second inner ring 108 are separate components. The first inner ring 106 may extend approximately from the first shaft portion 14 of the shaft 12 to the second inner ring 108. Similarly, the second inner ring 108 may extend approximately from the second shaft portion 16 of the shaft 12 to the first inner ring 106. The first and second inner rings 106, 108 may contact each other at a location approximately located between the first and second shaft portions 14, 16 of the shaft 12.The first and second inner rings 106, 108 may be mirrored symmetrically at the location approximately between the first and second shaft portions 14, 16 of the shaft 12.

[0033] In yet another embodiment, the bearing assembly 34 further includes a spacer 110 disposed between the first inner ring 106 and the second inner ring 108 to hold the first inner ring 106 between the first outer ring 88 and the shaft 12 and to hold the second inner ring 108 between the second outer ring 96 and the shaft 12. The spacer 110 may be disposed at the location approximately between the first and second shaft portions 14, 16 of the shaft 12. The spacer 110 is relatively inexpensive and allows the first and second inner rings 106, 108 to be smaller, thereby saving manufacturing costs of the first and second inner rings 106, 108. In the embodiments with the spacer 110, the first and second inner rings 106, 108 may also be mirrored symmetrically at the location located approximately between the first and second shaft portions 14, 16 of the shaft 12.

Claims

[1] A bearing assembly (34) for supporting the rotation of a shaft (12) in a turbocharger (10), the bearing assembly (34) comprising: an inner ring (36, 106, 108) extending along an axis (A) and configured to be coupled to the shaft (12), a first outer ring (88) which is radially spaced from the inner ring (36, 106, 108), a first cage (90) arranged radially between the inner ring (36, 106, 108) and the first outer ring (88), and a first rolling element (92) arranged radially between the first outer ring (88) and the inner ring (36, 106, 108) and arranged within the first cage (90) to assist the rotation of the shaft (12), a second outer ring (96) spaced from the first outer ring (88) along the axis (A) and radially spaced from the inner ring (36, 106, 108), a second cage (98) arranged radially between the inner ring (36, 106, 108) and the second outer ring (96), a second rolling element (100) arranged radially between the second outer ring (96) and the inner ring (36, 106, 108) and arranged within the second cage (98) to assist the rotation of the shaft (12), characterized by that the first outer ring (88) defines a primary lubricant passage (74) configured to direct lubricant toward the first cage (90), and that the first outer ring (88) defines a secondary lubricant passage (76), which is spaced from the primary lubricant passage (74) along the axis (A). [2] The bearing assembly (34) of claim 1, wherein the first cage (90) extends from a first cage end (56) at a first location (58) along the axis (A) to a second cage end (60) at a second location (62) along the axis (A) different from the first location (58), a distance (D) being defined between the first location (58) and the second location (62), and wherein the primary lubricant passage (74) is located within a lubricant boundary (LB) defined as being between 25% of the distance (D) from the first location (58) and 25% of the distance (D) from the second location (62). [3] The bearing assembly (34) of claim 1, wherein the first cage (90) extends from a first cage end (56) at a first location (58) along the axis (A) to a second cage end (60) at a second location (62) along the axis (A) different from the first location (58), and wherein at least a portion of the primary lubricant passage (74) is located between the first location (58) and the second location (62). [4] The bearing assembly (34) of claim 3, wherein the first outer ring (88) has an inner surface (64) facing the inner ring (36, 106, 108), the inner surface (64) of the first outer ring (88) defining an outlet (70) in fluid communication with the primary lubricant passage (74), at least a portion of the outlet (70) being located between the first location (58) and the second location (62), and optionally the entire outlet (70) being located between the first location (58) and the second location (62). [5] The bearing assembly (34) of claim 4, wherein the first cage (90) has an outer cage surface (80) facing the inner surface (64) of the first outer ring (88), and wherein the outlet (70) is configured to direct lubricant toward the outer cage surface (80) of the first cage (90). [6] Bearing assembly (34) according to one of claims 4-5, wherein the first cage (40, 90, 98) has a first outer portion (82) adjacent the first cage end (56) and having a first radial height (RH1), a second outer portion (84) adjacent the second cage end (60) having the first radial height (RH1), and a middle portion (86) axially disposed between the first outer portion (82) and the second outer portion (84), the middle portion (86) having a second radial height (RH2) less than the first radial height (RH1), and the outlet (70) is aligned with the first outer portion (82) of the first cage (90) or the second outer portion (84) of the first cage (90). [7] The bearing assembly (34) of claim 6, wherein the first cage (90) has an outer cage surface (80) facing the inner surface (64) of the first outer ring (88), the outer cage surface (80) extending at the first outer portion (82) at a first radial distance (RD1) from the axis (A), the outer cage surface (80) extending at the second outer portion (84) at the first radial distance (RD1) from the axis (A), the outer cage surface (80) extending at the middle portion (86) at a second radial distance (RD2) from the axis (A), the second radial distance (RD2) being less than the first radial distance (RD1), and the outlet (70) being aligned with the first outer portion (82) of the first cage (90) or the second outer portion (84) of the first cage (90). [8] Bearing assembly (34) according to one of claims 1-7, further comprising a squeeze film damper cup (78) which is rotationally fixed relative to the first outer ring (88) such that the first outer ring (88) is arranged radially between the squeeze film damper cup (78) and the inner ring (36, 106, 108). [9] The bearing assembly (34) of claim 8, wherein the primary lubricant passage (74) is defined by the squeeze film damper cup (78). [10] Bearing assembly (34) according to any one of claims 1-9, wherein the primary lubricant passage (74) is defined radially through the first outer ring (88) perpendicular to the axis (A). [11] Turbocharger (10) for supplying compressed air to an internal combustion engine, the turbocharger (10) comprising: A shaft (12) extending along an axis (A) between a first shaft portion (14) and a second shaft portion (16) spaced from the first shaft portion (14) along the axis (A), a compressor wheel (18) coupled to the first shaft portion (14) of the shaft (12), a turbine wheel (20) coupled to the second shaft portion (16) of the shaft (12), and the bearing assembly (34) according to any one of claims 1-10 for supporting rotation of the shaft (12).

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