Steering wheel mounting assembly

A steering wheel mounting assembly comprising a stationary support carrier, first and second drive rings, and a drive roller assembly. The stationary support carrier defines first and second ring receiving areas. The first drive ring has a first cylindrical raceway, is supported in the first ring receiving area, and is adapted for connection to a steering wheel. The second drive ring has a second cylindrical raceway, is positioned in the second ring receiving area, and is adapted for connection to a steering shaft. The drive roller assembly is supported within the first and second cylindrical raceways and comprises first and second roller planets, a sun roller supported in frictional engagement with the first and second roller planets, a first loading planet frictionally positioned between the sun roller and the first cylindrical raceway, and a second loading planet frictionally positioned between the sun roller and the second cylindrical raceway.

BACKGROUND

The present invention relates to a steering assembly. More particularly, the present invention relates to a steering assembly having a static hub with a steering wheel rotatable thereabout.

Referring toFIG. 1, a prior art steering assembly10is shown. The steering assembly10includes a steering wheel12mounted on a radial frame14. The radial frame14includes a central hub16that is mounted on a steering column18. Rotation of the steering wheel12is translated through the frame14, and thereby the hub16, to cause rotation of the steering column18.

A mounting frame20is attached to and rotates with the radial frame14. The mounting frame20is configured to support an air bag assembly22and other components. The air bag assembly22is fixed to the mounting frame20, and therefore, rotates with the steering wheel12. Since the orientation of the air bag assembly22continuously changes with rotation of the steering wheel12, the air bag assembly22must have a substantially symmetrical design so that the air bag thereof will deploy with a known configuration no matter the orientation of the air bag assembly22at the time of deployment.

Furthermore, it is not desirable to mount driver controls and displays on the mounting frame20since the mounting frame20rotates with the steering wheel12.

SUMMARY

The present invention relates to a steering wheel mounting assembly. The assembly comprises a stationary support carrier defining first and second ring receiving areas and adapted to be fixed to a vehicle frame. A first drive ring having a first cylindrical raceway is supported in the first ring receiving area and is adapted for connection to a steering wheel. A second drive ring having a second cylindrical raceway is positioned in the second ring receiving area and is adapted for connection to a steering shaft. The second cylindrical raceway is concentric with the first cylindrical raceway. A drive roller assembly is supported within the first and second cylindrical raceways. The drive roller assembly comprises first and second roller planets, each roller planet having raceways configured to engage the first and second cylindrical raceways. A sun roller is supported in frictional engagement with the first and second roller planets. The sun roller is eccentric to the first and second cylindrical raceways. A first loading planet is frictionally positioned between the sun roller and the first cylindrical raceway, and a second loading planet is frictionally positioned between the sun roller and the second cylindrical raceway.

DETAILED DESCRIPTION

The present invention will be described with reference to the accompanying drawing figures wherein like numbers represent like elements throughout. Certain terminology, for example, “top”, “bottom”, “right”, “left”, “front”, “frontward”, “forward”, “back”, “rear” and “rearward”, is used in the following description for relative descriptive clarity only and is not intended to be limiting.

Referring toFIGS. 2-6, a mounting assembly50that is a first embodiment of the present invention is shown. The mounting assembly50generally comprises a stationary support carrier60, a first drive ring100, a second drive ring120and a drive roller assembly140. The stationary support carrier60is configured for mounting to the vehicle frame (not shown). The first and second drive rings100and120are mounted within the stationary support carrier60. The drive roller assembly140provides rotational torque between the first drive ring100and the second drive ring120such that rotation of a steering wheel (not shown) attached to the first drive ring100would cause rotation of a steering shaft (not shown) attached to the second drive ring120. Cover plates170,170′ are provided to secure the drive roller assembly140within the stationary support carrier60. The front cover plate170is provided with means for supporting desired components, for example, an air bag assembly or driver controls and displays. In one embodiment, a wire tube190is provided to provide a wire passage from the stationary support carrier60through the front cover plate170.

An exemplary stationary support carrier60will be described with reference toFIGS. 2,4and7. The stationary support carrier60has a radial plate62. The radial plate62is provided with a plurality of threaded holes64for fastening the stationary support carrier60to the vehicle frame (not shown). The radial plate62is provided with a central opening66for receiving the drive roller assembly140. Three supporting columns, a lower column70and two side columns76and76, are attached to the radial plate62within the central opening66. Each of the supporting columns70,76,76has an axial width approximately equal to the width of the drive roller assembly140elements. The lower column70has a concave radially inner surface72. An open space83for the sun roller142is defined above the concave surface72. As shown inFIG. 4, the sun roller142is positioned in the open space83such that the sun roller142is eccentric to the axis A of the stationary support carrier60and the first and second drive rings100,120.

Each side surface74of the lower column70is also concave. Each lower column side surface74is opposed by a concave side surface77of a respective side column76. Each set of opposed side surfaces74,77defines a respective open space82configured to receive a respective one of the planet rollers150. The two side columns76have opposed concave surfaces79that define an open area84configured to receive the loading planets160. As shown inFIG. 4, the open space84is larger than the diameter of the loading planets160such that the loading planets160can move within the open area84as will be described hereinafter. As shown inFIG. 7, the lower column70and side columns76each have annular steps73and78, respectively, configured to position and support the cover plates170,170′ as will be described hereinafter.

The stationary support carrier60has a first annular wall86extending from the radial plate62to define an area88for receiving the first drive ring100. An annular step87at the conjunction of the radial plate62and the first annular wall86defines the axial position of the first drive ring100within area88. Once the first drive ring100is positioned within area88, it is further secured in the axial direction by a snap ring (not shown) or by roll forming the free end of the annular wall86, for example.

The stationary support carrier60has a second annular wall90extending from the other side of the radial plate62to define an area92for receiving the second drive ring120. An annular thrust bearing surface91is provided on the radial plate62to axially position the second drive ring120within the area92. An annular step93at the end of the wall90is configured to receive a thrust ring95, seeFIG. 3, to confine the axial position of the second drive ring120within the area92.

Referring toFIG. 8, an exemplary first drive ring100is shown. The first drive ring100includes an inner race ring102, a set of rolling elements114and an outer race ring110. The bore of the inner race ring102defines the cylindrical raceway104of the first drive ring100. There are through holes108on the body of the inner race ring102for connection with the steering wheel (not shown). The outer surface of the inner race ring102is provided with a rolling element raceway106, and the inner surface of the outer race ring110is provided with a rolling element raceway112. In the illustrated embodiment, the rolling elements114are balls and each of the raceways106,112is a circumferential groove configured to receive the balls. Other rolling elements and corresponding raceways may also be utilized. As shown in FIGS.3and5-6, the first drive ring100is positioned in the area88with the outer race ring110supported by the first annular wall86. The rolling elements114allow the inner race ring102, and the interconnected steering wheel (not shown), to rotate freely relative to the outer race ring110and thereby the stationary support carrier60.

Referring toFIG. 9, an exemplary second drive ring120is illustrated. The second drive ring120has an annular body122. The bore of the annular body122defines the cylindrical raceway123of the second drive ring120. The second drive ring120is radially supported and positioned by the engagement of the cylindrical raceway123with the drive roller assembly140as will be described hereinafter. The annular body122has two planar surfaces124and126for axial thrust bearing surfaces. Radially outer surface127extending between the planar surfaces124and126is configured to be spaced from the inner surface of the second annular wall90of the stationary support carrier60when the second drive ring120is positioned within the area92.

A shaft connector128is connected to the annular body122through a set of spokes134. The shaft connector128is provided with a through hole130, seeFIG. 3, and splines or keyways132for facilitating connection of a steering shaft or the like to the shaft connector128. Other connection arrangements may also be provided.

An exemplary drive roller assembly140will be described with reference toFIGS. 2-4and10-13. The drive roller assembly140generally comprises a sun roller142, a pair of planet rollers150and a pair of loading planets160. Referring toFIG. 10, an exemplary sun roller142has two cylindrical raceways144and146that are separated by a rib148. Referring toFIG. 11, exemplary planet rollers150each have two cylindrical raceways152and154separated by a recess156. At each end surface, there is a journal shaft158that lies in the same axis as the raceways152and154. By providing two raceways144,146and152,154on each of the sun and planet rollers142,150, the two drive rings100,120are compounded, having at least one common planet or sun roller, to communicate rotational movement and transfer torque from one ring member100to the other ring member120. While the sun roller142can be formed as a unitary component with a pair of raceways144,146, and the planet rollers150can be formed as unitary components with pairs of raceways152,154, it is possible to make one or two of these components as separated components with separate raceways. In an exemplary implementation, the sun roller142and planet rollers150are manufactured from a rigid material.

Referring toFIG. 12, each loading planet160has a cylindrical body162with an opening164therethrough. Each loading planet body162is flexible relative to the planet rollers150and the sun roller142. The loading planets160deform in a diametric direction when assembled between the first and second drive rings100,120and the sun roller142. This provides a preload that pushes the sun roller142downward as will be described hereinafter.

Referring toFIGS. 2-5and13, the sun roller142, planet rollers150and the loading rollers160are retained axially within the stationary support carrier60by attachment of cover plates170,170′ to the supporting columns70,76,76. Each cover plate170,170′ is provided with two bearing sleeves176configured to respectively receive the journal shaft158extending from the planet rollers150. As shown inFIG. 13, the front cover plate170is provided with mounting features, for example, connection holes180,182, for mounting an air bag assembly, instrument panels or displays. The front cover plate170is also provided with a primary through hole174and a secondary through hole178. The secondary through hole178is configured to receive and support a portion of the wire tube190as will be described hereinafter. The rear cover plate170′ can be formed in the same configuration as the front cover plate170to minimize manufacturing. However, the rear cover plate170′ can be formed without mounting features and the secondary through hole178.

Referring toFIGS. 4-6, the drive roller assembly140is positioned in the stationary support carrier60with the sun planet142in opening83, the roller planets150in respective openings82, and the loading planets160positioned in the opening84. The roller planets150are supported by the first and second drive rings100and120with the first raceways152bearing on the first drive ring cylindrical raceway104and the second raceways154bearing on the second drive ring cylindrical raceway123. Each journal shaft158is received in and supported by a respective bearing sleeve176.

The sun roller142is supported between and in frictional contact with the two roller planets150. The sun roller rib148is received in each planet roller recess156to maintain the sun roller142axially aligned with the planet rollers150. The planet roller raceways152bear against the sun roller raceway144and the planet roller raceways154bear against the sun roller raceway146. The sun roller142is supported below the axis A of the stationary support carrier60and first and second drive rings100,120such that the sun roller142is eccentric to the first and second drive rings100,120.

One of the loading planets160is positioned between sun roller raceway144and the first drive ring cylindrical raceway104and a second of the loading planets160is positioned between the sun roller raceway146and the second drive ring cylindrical raceway123. In an exemplary construction, the loading planets160have a diameter greater than the respective distances between the sun raceways144and146and the ring drive raceways104and123such that the loading planets160provide a preload on the sun roller142. The sun roller rib148axially positions the loading planets160as shown inFIG. 4.

A wire passage is provided by the wire tube190as shown inFIGS. 2-3and5-6. The wire tube190has a radial portion192that provides a radial passage194and an axial portion196that provides an axial passage198interconnected with the radial passage194. The axial portion196is provided with a mounting recess199configured to snap on to the secondary through hole178of the cover plate170. The axial portion196extends through the opening164of one of the loading rollers160and the radial portion192extends between an axial gap between the two loading rollers160and through an opening68cut in the stationary supporting carrier60.

Having described the components of the mounting assembly50according to an embodiment of the present invention, its operation will now be described with reference toFIGS. 4 and 14. The roller planets150back up the sun roller142. The downward force F0(loading force) from the loading planets160on the sun roller142is balanced by the backing forces Fb, from the roller planets150as shown inFIG. 14. The angle between the two backing forces, denoted as α, can be designed close to 180 degrees. Thus, a small loading force Focan result in large backing forces Fbwhich in turn cause large normal contact force between the roller planets150and the drive rings100,120. These large normal contact forces provide adequate friction force between the roller planets150and the drive ring100,120to ensure torque transfer between the two drive rings100,120.

As the operator steers the vehicle, the first drive ring inner race ring102turns with the steering wheel (not shown) in the same direction. Contact between the first drive ring inner ring raceway104and the roller planet raceways152and the loading planet160causes the roller planet raceways152and the loading planet160to rotate in the same direction as the first drive ring inner ring102. Motion of the first drive ring inner ring102pulls the loading planet160into a convergent gap formed between the first drive ring inner ring102and the sun roller142. This further increases the loading force F0for the first drive ring100. The roller planets150consequently drive the sun roller142in the opposite direction. As the sun roller142rotates, it also pulls the other loading planet160into a convergent gap formed between the second drive body122and the sun roller142. This, in a similar way, further increases the loading force Fofor the second drive ring120. As the roller planets150rotate, they drive the second drive ring120in the same direction as the planet rollers150and the first drive ring inner ring102. Therefore, the drive roller assembly140provides a 1:1 speed ratio between the two ring drives100and120. Any overturning moment on the first drive ring inner ring102from the steering wheel is taken directly by the rolling elements114to the stationary supporting carrier60. Co-owned U.S. patent application Ser. No. 10/298,762, filed Nov. 18, 2002 and incorporated herein by reference, further describes an exemplary embodiment of the drive roller assembly140.

Embodiments of the present invention provide substantially zero backlash at frictional contacts. For example, in implementations described above, there will be substantially no lash between the first drive ring100connected to a steering wheel and the second drive ring120connected to the steering shaft. Furthermore, the drive roller assembly140is smooth and quiet in operation. In general, embodiments of the friction drive disclosed herein eliminate the lash and variation in torque typically experienced during operation of gear-driven steering systems. Moreover, it can be appreciated that embodiments enable the integration of shaped airbags to improve vehicle safety, as well as the placing of vehicle gage(s), controls, and/or LCD display(s) in the center of the steering wheel without the need for clock springs.

The embodiments described above are merely exemplary embodiments, and other embodiments can be practiced that fall within the scope of embodiments of the invention.