Mounting of a shaft within a housing with a preloaded bearing

Abstract: An angular contact bearing is mounted within a housing (26) and a shaft (24) is positioned within the bearing such that an annular space is provided between the bearing and the shaft. A mounting ring (32) of elastomeric polymer is positioned over the shaft and against a bearing inner ring (34) such that a portion of the mounting ring is between the bearing inner ring and the shaft, centring the shaft within the bearing and reducing radial freeplay. The mounting ring is compressed axially, against the bearing, such that the mounting ring deforms and resiliently spreads radially outwardly and provides a preload on the bearing balls.

Description: This invention relates generally to the mounting of a rotatable shaft within a housing and, more particularly, to a mounting suitable for a steering column shaft. Typically, automotive tilt steering columns require a spring preload to eliminate axial free play and a steel tolerance ring to eliminate radial free play. Currently, a steel coil spring or wave type spring is used in combination with a steel or plastic tolerance ring. This mounting arrangement requires a great amount of axial space and introduced variations in torque-to-rotate. Additionally, such mounting arrangements allow transmission of noise and vibration to or from the shaft, through the bearing. US-A-4 456 314 discloses a known way of mounting an inner bearing ring on a shaft. According to the present invention, there is provided a method of mounting a shaft within a housing, the method comprising mounting an angular contact bearing within the housing, the angular contact bearing having bearing balls between a bearing outer ring and a bearing inner ring, the annular contact bearing having an axis; and positioning a shaft within the bearing inner ring such that an annular space is provided between the bearing inner ring and the shaft; characterised by positioning a mounting ring formed of elastomeric polymer over the shaft and against the bearing inner ring such that a portion of the mounting ring is within the annular space between the bearing inner ring and the shaft such that the bearing inner ring is spaced from and in a non-contact position relative to the shaft, thereby centring the shaft within the bearing inner ring and reducing radial free play of the shaft with respect to the bearing inner ring; and compressing the mounting ring axially, against the bearing inner ring, such that the mounting ring deforms and resiliently spreads radially outwardly and provides a preload on the bearing balls. According to another aspect of the present invention, there is provided an assembly comprising a housing, an angular contact bearing having bearing balls between a bearing outer ring and a bearing inner ring, the bearing outer ring being mounted within the housing, the bearing inner ring having a central annular aperture; there being a shaft located concentrically within the central annular aperture of the bearing inner ring such that an annular space is provided between the bearing inner ring and the shaft and there being stop means mounted on the shaft; characterised by a mounting ring, formed of elastomeric polymer, having a portion located within the annular space between the bearing inner ring and the shaft, such that the bearing inner ring is spaced from and in a non-contact position relative to the shaft the mounting ring being compressed axially between the bearing inner ring and the stop means such that the mounting ring is resiliently spread radially outwardly and a preload is exerted on the bearing balls. For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example to the accompanying drawings, in which:- Fig. 1 is a sectional view of a shaft mounted within a housing illustrating the prior art; Fig. 2 is a sectional view of a shaft mounted within a housing, illustrating a first embodiment of the present invention; Fig. 3 is a sectional view of a shaft mounted within a housing, illustrating a second embodiment; Fig. 4 is a sectional view illustrating an elastomeric polymer mounting ring of the embodiments of Figs. 2 and 3 prior to axial compression of the mounting ring; and Fig. 5 is a sectional view of a shaft mounted within a housing, illustrating a third embodiment. Figure 1 illustrates a shaft 10 mounted within a housing 12 by angular contact bearings 14 and 16. A steel tolerance ring 18 is split or segmented so that it can close radially inwardly against shaft 10 and under a tapered portion of a bearing inner ring 20 of the angular contact bearing 14 to reduce radial free play between the shaft 10 and bearing inner ring 20. Steel coil spring 22 provides an axial preload on the angular contact bearings 14 and 16 by pressing axially against the steel tolerance ring 18. Figure 2 illustrates a first embodiment of the present construction having a shaft 24 mounted within a housing 26 by angular contact bearings 28 and 30 that form a clearance fit with the shaft. A mounting ring 32, formed of an elastomeric polymer, is located against a bearing inner ring 34 of the angular contact bearing 28, such that a wedge-shaped portion of the mounting ring 32 is between the bearing inner ring 34 and shaft 24. As a result of this positioning of the mounting ring 34, radial free play of the shaft is reduced and the shaft is centred and isolated from contact with the housing and bearings, reducing transmission of noise and vibration to or from the shaft. Preferably, the angular contact bearings 28 and 30 are mounted within the housing 26 before inserting (or sliding) the shaft 24 into position within the bearings. Various mounting means may be used; for example, bearing outer rings 36 and 38 may be press-fit into housing 26 axially inwardly against a shoulder of housing 26. For convenience, angular contact bearings 28 and 30 may include bearing retainers 40 with radially extending flanges or tabs 42 and 44 that hold the bearings together as a subassembly prior to mounting of the shaft 24 and application of a preload. In the embodiment of Figure 2, the shaft 24 has a radially outwardly tapered annular shoulder 46 that engages a mating tapered inner surface of the bearing inner ring 48 of the angular contact bearing 30. An annular washer 50, held by a snap ring 52, or other stop means compresses the mounting ring 32 axially, against the bearing inner ring 34. As a result of this axial compression, the mounting ring 32 deforms and resiliently spreads radially outwardly and provides a preload on bearing balls 54 of angular contact bearings 28 and 30, acting through the housing 26 and resisted by engagement of the bearing inner ring 48 with annular shoulder 46. Figure 3 illustrates a second embodiment of the present construction including an optional wedge-shaped isolator 56, formed of elastomeric polymer, between the bearing inner ring 48 and the annular shoulder 58 of a shaft 60. The annular shoulder 58 and the radial surface engaging wedge-shaped isolator 56 to force the point of the wedge between the bearing inner ring 48 and shaft 60 to centre the shaft and present contact between angular contact bearing 30 and the shaft. This isolation of the shaft 60 provides further reduction of transmitted noise and vibration to or from the shaft. Other elements of this embodiment are similar to those of the first embodiment. The mounting member 32 is shown in its undeformed cylindrical sleeve configuration 62 in Figure 4. Figure 5 illustrates a third embodiment similar to the second embodiment and including the wedge-shaped isolator 56. A shaft 60 has an annular shoulder 66 similar to the annular shoulder 58 and includes a reduced diameter portion forming step 60 located radially inwardly of the bearing inner ring 34. The step 72 allows mounting ring 70 to have a thicker radial section than the mounting ring 32 while providing a wedge-shaped portion for engaging a radially outwardly tapered surface of the bearing inner ring 34. When held by a snap ring 74 as shown, the mounting ring 70 is axially compressed and resiliently spread radially outwardly to provide a preload on the angular contact bearings 28 and 30. Although other elastomeric polymers may be used, urethane is particularly suited as a material for this use because it is not readily compressible but resiliently deforms within changing its volume and without creep or relaxation under load. When the mounting member 32 or 70 is "compressed axially", as described above, the volume remains substantially the same as it is deformed radially outwardly while maintaining contact with the shaft. As a result of this resilient deformation, a desired torque-to-rotate is maintained with less variation than can be obtained with known mounting arrangements while accommodating large axial displacements of the shaft and housing. It will be appreciated that the present construction provides substantial improvements with respect to reduction of noise and vibration and maintenance of uniform torque-to-rotate of the shaft relative to the housing, making it ideal for mounting automotive tilt steering columns. In addition, the present construction requires fewer parts than known mounting arrangements, resulting in simpler assembly and requires less axial space.

Claims: A method of mounting a shaft (24) within a housing (26), the method comprising mounting an angular contact bearing (28) within the housing, the angular contact bearing having bearing balls (54) between a bearing outer ring (36) and a bearing inner ring (34), the annular contact bearing having an axis; and positioning a shaft (24) within the bearing inner ring such that an annular space is provided between the bearing inner ring and the shaft; characterised by positioning a mounting ring (32) formed of elastomeric polymer over the shaft (24) and against the bearing inner ring (34) such that a portion of the mounting ring is within the annular space between the bearing inner ring and the shaft such that the bearing inner ring (34) is spaced from and in a non-contact position relative to the shaft (24), thereby centring the shaft within the bearing inner ring and reducing radial free play of the shaft with respect to the bearing inner ring; and compressing the mounting ring (32) axially, against the bearing inner ring (34), such that the mounting ring deforms and resiliently spreads radially outwardly and provides a preload on the bearing balls (54). A method according to claim 1, wherein the bearing inner ring (34) has an outwardly tapered radially inner surface corresponding to an outwardly tapered radially outward surface of the portion of the mounting ring (32) between the bearing inner ring and the shaft (24) such that positioning the mounting ring within the annular space between the bearing inner ring and the shaft is facilitated. A method according to claim 1 or 2, further comprising mounting of a second angular contact bearing (30) within the housing (26), the second angular contact bearing having bearing balls (54), and being engageable with a stop surface (58) on the shaft such that the axial compression of the mounting ring (32) provides a preload on the bearing balls (54) of the second angular contact bearing. A method according to claim 3, further comprising positioning a wedge-shaped isolator (56) formed of elastomeric polymer between the shaft (60) and the second angular contact bearing (30) and engageable with the stop surface on the shaft, thereby facilitating centring of the shaft and reducing radial free play of the shaft with respect to the second angular contact bearing. A method according to any one of the preceding claims, wherein the mounting ring (32) is formed of urethane. An assembly comprising a housing (26), an angular contact bearing (28) having bearing balls (54) between a bearing outer ring (36) and a bearing inner ring (34), the bearing outer ring being mounted within the housing, the bearing inner ring having a central annular aperture; there being a shaft (24) located concentrically within the central annular aperture of the bearing inner ring such that an annular space is provided between the bearing inner ring and the shaft and there being stop means (50) mounted on the shaft; characterised by a mounting ring (32), formed of elastomeric polymer, having a portion located within the annular space between the bearing inner ring (34) and the shaft (24) such that the bearing inner ring (34) is spaced from and in a non-contact position relative to the shaft (24), the mounting ring being compressed axially between the bearing inner ring and the stop means (50) such that the mounting ring is resiliently spread radially outwardly and a preload is exerted on the bearing balls. An assembly according to claim 6, wherein the central annular aperture of the bearing inner ring (34) has an outwardly tapered radially inner surface corresponding to an outwardly tapered radially outward surface of the portion of the mounting ring (32), between the bearing inner ring and the shaft (24). An assembly according to claim 6 or 7, further comprising a second angular contact bearing (30) mounted within the housing and a stop surface (58) on the shaft, the second angular contact bearing abutting the stop surface and having bearing balls (54) preloaded by the axially compressed mounting ring. An assembly according to claim 7, further comprising a wedge-shaped isolator (56) formed of elastomeric polymer between the shaft (24) and the second angular contact bearing (30) and abutting the stop surface (58) on the shaft such that centring of the shaft and reducing radial free play of the shaft with respect to the second angular contact bearing are facilitated. An assembly according to claim 6, 7, 8 or 9, wherein the mounting ring (32) is formed of urethane. An assembly according to any one of claims 6 to 10, wherein the shaft (52) has a reduced diameter portion forming a step (72) located radially inwardly of the bearing inner ring (34) and wherein the mounting ring (70) is located on the reduced diameter portion and against the step.

Inventors: BEAMAN MICHAEL D, BEAMAN, MICHAEL D.
Applicants: TORRINGTON CO, THE TORRINGTON COMPANY
Application year: 1998
Main classification: F16C25
IPC codes: F16C25, F16C35