Flex coupling assembly with restrictive bending feature

A flex coupling assembly for coupling a first shaft to a second shaft of a shaft assembly. The flex coupling assembly includes a lower housing having a housing wall bounding a cavity between a first end having an end face and an open second end. A first shaft is fixed to the end face and extends along an axis. An upper flange, spaced from the lower housing, has a second shaft fixed thereto extending along the axis. A retention member, disposed in the cavity, is operably fixed to the upper flange. A resilient flex coupling, disposed between the end face and the flange, is operably fixed to the upper flange and the retention member and to the lower housing. The lower housing and the flange are moveable axially toward and away from one another and rotatably about the axis via flexing of the resilient flex coupling which dampens noise and vibrations between the first and second shafts.

FIELD OF THE INVENTION

The present disclosure generally relates to shaft assemblies for motor vehicles, and more specifically, to flex coupling assemblies for joining shafts of a shaft assembly together.

BACKGROUND OF THE INVENTION

Automotive shaft assembly applications, such as steering shaft applications, commonly join shafts of a shaft assembly to one another with a dampening coupler. The dampening coupler is provided between the shafts of the steering shaft to dampen noise and vibration to isolate a driver from unwanted noise and vibrations coming from the engine bay and road. Although known dampening couplers can prove effective in reducing the amount of noise and vibration that reaches the driver, they typically reduce the bending stiffness of the shaft assembly. Increased bending stiffness requirements for shaft assemblies are being required by manufacturers, thereby causing the overall effectiveness of the dampening coupler to be compromised in its ability to dampen noise and vibration in order to meet the bending stiffness requirements. Accordingly, the noise and vibration dampening characteristics of flex couplers is being sacrificed in order to meet the bending stiffness requirements. Accordingly, what is needed is a dampening coupler that meets or exceeds both the increased demands for bending stiffness, while at the same time providing the level of noise and vibration dampening desired to prevent noise and vibration from reaching the driver.

SUMMARY OF THE INVENTION

It is an object of the present disclosure to provide a flex coupling assembly for coupling a first shaft of a shaft assembly to a second shaft of the shaft assembly that overcomes at least some of the drawbacks discussed above with known dampening couplers.

It is a further object of the present disclosure to provide a flex coupling assembly that is robust and durable in use, and economical in manufacture and assembly.

It is a further object of the present disclosure to provide a flex coupling assembly that decouples axial and torsional stiffness from bending stiffness, thereby allowing more freedom in design to tune the performance of the decoupling between first and second shafts.

It is a further object of the present disclosure to provide a flex coupling assembly that provides an ability to adjust the bending stiffness of the flex coupling assembly without affecting the torsional stiffness and the axial stiffness and noise and vibration dampening performance of the flex coupling assembly.

It is a further object of the present disclosure to provide a flex coupling assembly that provides an ability to adjust the torsional stiffness of the flex coupling assembly without affecting the bending stiffness and the axial stiffness and noise and vibration dampening performance of the flex coupling assembly.

It is a further object of the present disclosure to provide a flex coupling assembly that provides an ability to adjust the axial stiffness of the flex coupling assembly without affecting the bending stiffness and the torsional stiffness and noise and vibration dampening performance of the flex coupling assembly.

According to the objects and advantages, an aspect of the present disclosure provides a flex coupling assembly for coupling a first shaft of a shaft assembly to a second shaft of the shaft assembly. The flex coupling assembly includes a lower housing having a generally cylindrical housing wall extending along an axis and bounding a cavity between a lower housing first end and a lower housing second end. The lower housing first end has an end face extending generally transversely to the axis to generally closing off the cavity. The lower housing second end is generally open to the cavity. A first shaft is fixed to the end face of the lower housing and extends along the axis away from the cavity. An upper flange is spaced axially from the lower housing. A second shaft is fixed to the upper flange and extends along the axis. A retention member is disposed in the cavity of the lower housing and is fixed to the upper flange by a plurality of retention fastener members. A resilient flex coupling is sandwiched between the end face of the lower housing and the flange. The resilient flex coupling is fixed to the upper flange and to the retention member by the plurality of retention fastener members. The resilient flex coupling is fixed to the lower housing by a plurality of coupling fastener members. The lower housing and the flange are moveable relative to one another axially in opposite axial directions along the axis and rotatably about the axis via flexing of the resilient flex coupling.

In accordance with another aspect of the disclosure, the lower housing end face has a plurality of through openings and the plurality of retention fastener members extend through the plurality of through openings in clearance relation therewith. The plurality of through openings act as positive stops to limit the degree of relative rotation between the lower housing and the upper flange. The size of the through openings can be optimized, as desired, to provide the degree of relative movement desired for the specific application.

In accordance with another aspect of the disclosure, the lower housing has a plurality of fastener receptacles extending in parallel relation to the axis in the cavity. The plurality of fastener receptacles receive the plurality of coupling fastener members therethrough. The retention member has a plurality of slots sized for a clearance fit with the plurality of fastener receptacles, wherein said plurality of slots act as positive stops to limit the degree of relative rotation between the lower housing and the upper flange. The circumferentially extending width of the slots can be optimized, as desired, to provide the degree of relative movement desired for the specific application.

In accordance with another aspect of the disclosure, the plurality of through openings and the plurality of slots are circumferentially offset from one another to allow the axially extending package size of the flex coupling assembly to be minimized.

In accordance with another aspect of the disclosure, a plurality of spacer members are provided to receive the plurality of retention fastener members therethrough. The plurality of spacer members extend through the plurality of through openings in clearance relation therewith into engagement with the retention member and the resilient flex coupling.

In accordance with another aspect of the disclosure, the generally cylindrical housing wall and the retention member are spaced radially from one another by a gap and at least one bushing disposed in the gap, wherein the at least one bushing can be provided having a radial thickness, as desired, to regulate the bending stiffness across the flex coupling assembly between the first and second shafts, and wherein the material of at least one bushing can be provided, as desired, to optimize the amount friction against an inner surface of the cylindrical housing wall.

In accordance with another aspect of the disclosure, at least one bushing can be provided as a pair of bushings arranged diametrically opposite one another.

In accordance with another aspect of the disclosure, at least one bushing is fixed to one of the generally cylindrical inner housing wall and the retention member.

In accordance with another aspect of the disclosure, the resilient flex coupling can be provided having a metal core overmolded with an elastomeric body.

In accordance with another aspect of the disclosure, the resilient flex coupling has a first side with a plurality of first protrusions extending axially outwardly therefrom into engagement with the end face of the lower housing and a second side with a plurality of second protrusions extending axially outwardly therefrom into engagement with the upper flange. The first and second protrusions provide pivot locations for axial deflection of the resilient flex coupling thereabout to allow for axial movement between the first and second shafts, as desired. The axial height of the first and second protrusions can be provided as desired to regulate the amount of axial deflection, as desired for the intended application.

In accordance with another aspect of the disclosure, the plurality of first protrusions includes a pair of first protrusions arranged diametrically opposite one another and the plurality of second protrusions includes a pair of second protrusions arranged diametrically opposite one another, said first pair of protrusions being arranged in circumferentially offset relation with said second pair of protrusions.

In accordance with another aspect of the disclosure, a flex coupling assembly for coupling a first shaft of a shaft assembly to a second shaft of the shaft assembly includes, a lower shaft subassembly, an upper shaft subassembly, and a flex coupling sandwiched between the lower shaft subassembly and the upper shaft subassembly and operably connecting the lower shaft subassembly to the upper shaft subassembly. The lower shaft subassembly includes a lower housing having a generally cylindrical housing wall extending along an axis and bounding a cavity between a lower housing first end and a lower housing second end. The lower housing first end has an end face extending generally transversely to the axis and a lower housing first shaft is fixed to the end face. The first shaft extends along the axis away from the cavity. The upper shaft subassembly includes an upper flange and an upper second shaft fixed to the upper flange, with the second shaft extending along the axis, and a retention member fixed to the upper flange by a plurality of retention fastener members. The resilient flex coupling that operably couples the lower shaft subassembly to the upper shaft subassembly allows the lower housing and the flange to move relative to one another axially along the axis and rotatably about the axis via flexing of the resilient flex coupling. The resilient flex coupling is fixed between the upper flange and the retention member by the plurality of retention fastener members. The resilient flex coupling is fixed to the lower housing by a plurality of coupling fastener members.

These and other objects, advantages and features will become readily apparent to one possessing ordinary skill in the art in view of the following description taken in conjunction with the drawings.

DETAILED DESCRIPTION

Referring now to the Figures, where the invention will be described with reference to specific embodiments, without limitation,FIG.1illustrates a motor vehicle10having a flex coupling assembly12(identified inFIGS.2-5) arranged in accordance with one aspect of the disclosure for coupling a first shaft14of a shaft assembly15to a second shaft16of the shaft assembly15. In the non-limiting, exemplary embodiment illustrated, the flex coupling assembly12is integrated into a steering system18of the motor vehicle10, although it is contemplated herein that the flex coupling assembly12could be integrated into other shaft assemblies, including a drive shaft assembly20, axle assembly22, or otherwise. The flex coupling assembly12, as discussed further hereafter, provides an ability to regulate the bending stiffness of the shaft assembly15without affecting the torsional stiffness, axial stiffness and dampening performance of the flex coupling assembly12. Thus, it is to be recognized that the bending stiffness across the flex coupling assembly12is isolated and decoupled from the axial and torsional stiffness of the flex coupling assembly12, thereby providing an ability to adjust the bending stiffness, as desired, without affecting the torsional stiffness, axial stiffness and dampening performance of the flex coupling assembly12.

The flex coupling assembly12has an upper shaft subassembly24(FIG.7), a lower shaft subassembly26(FIGS.8,9A and9B), and a flex coupling42sandwiched between the upper shaft subassembly24and the lower shaft subassembly26and operably connecting the upper shaft assembly24to the lower shaft assembly26. The lower shaft subassembly26includes a lower housing28having a generally cylindrical housing wall30extending along an axis A. The housing wall30bounds a cavity32that extends between a lower housing first end34and a lower housing second end36. The lower housing first end34has a lower housing end wall, also referred to as end face38, extending along a plane generally transversely to the axis A. The lower housing end face38has at least one, and shown as a plurality, and more particularly a pair of diametrically opposite through openings39shown being diametrically opposite one another, by way of example and without limitation. The lower housing end face38further at least one, and shown as a plurality, and more particularly a pair of diametrically opposite fastener receptacles, also referred to as fastener openings41, shown being diametrically opposite one another, by way of example and without limitation. The fastener openings41and the through openings39are arranged in circumferentially offset relation with one another, shown as being offset by about 90 degrees with one another. The lower housing second end36is open, shown as having the generally cylindrical inner housing wall30terminating a circular free edge. The lower shaft subassembly26further includes a lower housing first shaft40fixed to the lower housing end face38, such as via a weld joint, by way of example and without limitation, with the first shaft40extending coaxially along the axis A away from the lower housing cavity32.

The resilient flex coupling42, as shown inFIG.6, has a resilient, relatively rigid core44, overmolded with an elastomeric body46. The core44can be formed from a metal material, such as a metal plate or wound wire, by way of example and without limitation. The elastomeric body46can be formed of rubber or some other polymeric material. The resilient flex coupling42has at least one, and shown as a plurality of fastener openings48extending through opposite sides50,52. The fastener openings48can be provided via crush resistant tubular inserts, also referred to as bushings49. The bushings49can be made of metal or a high crush strength polymeric material. One of the sides, referred to hereafter as first side50, has a pair of protrusions, also referred to as first bosses54a, extending axially outwardly therefrom. The first bosses54aare arranged diametrically opposite one another. The other of the sides, referred to hereafter as second side52, has a pair of protrusions, also referred to as second bosses54b, extending axially outwardly therefrom. The second bosses54bare arranged diametrically opposite one another. The first bosses54aand the second bosses54bare arranged in circumferentially offset relation with one another, shown as being offset by about 90 degrees with one another. The offset, out-of-phase relation facilitates axial flexing of the resilient flex coupling, as desired to reduce the transmission of noise and vibration between the first and second shafts14,16. The resilient flex coupling42is fixed to the lower housing28via a plurality of coupling fasteners56, shown as a pair of threaded fasteners56extending through a pair of the fastener openings48in the flex coupling42into threaded engagement with the threaded fastener openings41in the inner housing end face38. Upon being fixed to the lower housing28, the bosses54aare brought into engagement with an outer surface of the lower housing end face38and the first side50is spaced axially from the outer surface of the lower housing end face38by an axial height of the bosses54a. The bushings49function to prevent axial compression of the respective bosses54a,54b, while facilitating deflection of the resilient flex coupling42, as desired and as discussed herein to allow controlled and limited relative axial movement between the first and second shafts14,16.

The upper shaft subassembly24includes an upper flange60having a generally planar wall62, shown as being generally rectangular. The wall62has a plurality, and shown as a pair of fastener openings64configured for receipt of a plurality of retention fasteners72therethrough. The upper shaft subassembly24further includes a second shaft66fixed to the upper flange60, such as via a press fit within a central opening68, a weld joint, or an adhesive, by way of example and without limitation, with the second shaft66extending coaxially along the axis A. The upper shaft assembly24further includes a retention member70fixed to the upper flange60by the plurality, and shown as a pair, of retention fastener members72. The resilient flex coupling42that operably couples the lower shaft subassembly26to the upper shaft subassembly24and allows the lower housing28and the flange60to move relative to one another axially along the axis A and rotatably about the axis A via flexing of the resilient flex coupling42. The resilient flex coupling42is fixed between the upper flange60and the retention member70by the plurality of retention fastener members72, and the resilient flex coupling42is fixed to the lower housing28by the plurality of coupling fastener members56, wherein the resilient flex coupling42is sandwiched between the end face38of the lower housing28and the upper flange60.

The retention member70is disposed in the cavity32of the lower housing28and is fixed to the upper flange60by the plurality of retention fastener members72. The plurality, shown as a pair, of fastener members72extend through the through openings39of the end face38in clearance relation therewith, wherein the plurality of through openings39act as a positive stop to limit the degree of relative rotation between the lower housing28and the upper flange60. A plurality of spacer members74are configured to receive the plurality of retention fastener members72therethrough. The plurality of spacer members74extend through the plurality of through openings39in clearance relation therewith, shown as extending into the cavity32, into engagement with both the retention member70and the resilient flex coupling42. The spacer members74are illustrated, by way of example and without limitation, as having an enlarged head76at one end for engagement with the resilient flex coupling42so as to avoid locally deforming the resilient flex coupling42in the area of engagement therewith. The through openings39provide a clearance fit with the spacer members74and act as a positive stop upon coming into engagement with the spacer members74to limit, as predetermined by controlling the size of the clearance fit, the degree of relative rotation between the lower housing28and the upper flange60.

The fastener receptacles41are shown as elongate bosses extending along an inner surface of the wall30in the cavity32. The fastener receptacles41extend in parallel relation to the axis A, with the plurality of fastener receptacles41receiving the plurality of coupling fastener members56therethrough. The retention member70has a plurality, shown as a pair of diametrically opposite notches, also referred to as slots78(FIG.9B), sized for a clearance fit with the plurality of fastener receptacles41. The clearance fit can be controlled as desired to limit the degree of relative rotation between the lower housing28and the upper flange60. Accordingly, in addition to the through openings39, the slots78act as rotational positive stops, wherein the plurality of through openings39and the plurality of slots78are circumferentially offset from one another. Upon the enlarged heads76of the spacer members74engaging radially extending peripheries80of the through openings39(FIG.9A, illustrating that the enlarged heads76do not fit through the through openings39, thereby requiring a unidirectional assembly of retention fastener members72through the through openings39, as will be understood by one possessing ordinary skill in the art), and/or upon radially extending sides82of the slots78engaging the fastener receptacles41(FIG.9B), the first and second shafts40,66become rotationally locked in conjoint rotation with one another. Of course, it is to be recognized that upon the torque between the first and second shafts40,66being reduced, the resiliency of the resilient flex coupling42imparts a bias between the lower housing28and upper flange60causing a re-centering, relaxed positioning between the peripheries80with the spacer members74and between the sides82of the slots78and the fastener receptacles41.

As mentioned above, the upper shaft assembly24and the lower shaft assembly26are able to move axially relative to another via axial translation and flexing of the resilient flex coupling42. An axial clearance “X” between radially extending positive stop surfaces88of the enlarged heads76and radially extending positive stop surfaces90of lower housing28, and an axial clearance “Y” between a radially extending positive stop surface92of retention member70and a radially extending positive stop surface94of first shaft40permits the lower housing28and the flange60, and thereby the lower shaft assembly26and upper shaft assembly24, to move axially relative to one another under an axial load applied to at least one of the first and second shafts40,66along axis A. It is to be recognized that the positive stop surface94of the first shaft40can be formed as a monolithic piece of material with the first shaft, or it can be provided as a separate piece of material fixed to the first shaft40, as will be understood by one possessing ordinary skill in the art. As such, axial telescopic dampening is provided between the first and second shafts40,66, wherein the dampening is facilitated and controlled by the axial flex rigidity provided by the resilient flex coupling42. Upon the respective positive stop surfaces88,90coming into engagement with one another (FIG.10A), the first and second shafts40,66become substantially fixed against compressive axial movement toward one another, and upon the respective positive stop surfaces92,94coming into engagement with one another (FIG.10B), the first and second shafts40,66become substantially fixed against tensile axial movement away from one another. Of course, it is to be recognized that upon the axial force between the first and second shafts40,66causing axial movement between the first and second shafts44,66being reduced, the resiliency of the resilient flex coupling42imparts an axial bias between the upper and lower shaft subassemblies24,26causing the lower housing28and upper flange60to return to their relaxed, as assembled axial positions (FIG.10). InFIG.10A, the upper and lower shaft subassemblies24,26are shown axially compressed toward one another with the positive stop surfaces88,90of the enlarged heads76and the lower housing28, respectively, engaging one another and with the resilient flex coupling42being resiliently flexed in a first axial direction, with the enlarged heads76and the upper flange60remaining engaged with opposite ends of the bosses54B, while inFIG.10B, the upper and lower shaft subassemblies24,26are shown axially extended away from one another with the positive stop surfaces92,94of the retention member70and the first shaft40, respectively, engaging one another and with the resilient flex coupling42being resiliently flexed in a second axial direction opposite the first axial direction ofFIG.10A, with the enlarged heads76and the upper flange60remaining engaged with opposite ends of the bosses54B, as will be understood by a person possessing ordinary skill in the art upon view the entirety of the disclosure herein.

The generally cylindrical housing wall30and the retention member70are spaced radially from one another by a uniform, constant gap G (FIG.9B) along diametrically opposite sides of the retention member70, over regions extending between the slots78in the retention member70. At least one bushing, and shown as a pair of diametrically opposite bushings86are disposed in diametrically opposite gaps G. The bushings86are fixed to one of an inwardly facing surface of the generally cylindrical inner housing wall30and an outwardly facing surface of the retention member70and free relative to the other of the generally cylindrical inner housing wall30and an outwardly facing surface of the retention member70. The bushings86are shown as being circumferentially discontinuous due to the presence of the fastener receptacles41. The bushings86can be fixed to the desired generally cylindrical inner housing wall30or outwardly facing surface of the retention member70via at least one of a press fit, a weld joint, an adhesive, or otherwise. To further facilitate retention of the bushings86to the respective generally cylindrical inner housing wall30or outwardly facing surface of the retention member70, the respective generally cylindrical inner housing wall30or outwardly facing surface of the retention member70could be provided with a lip, such as a curled lip (inwardly for the lower housing wall30and outwardly for the retention member70) to retain the bushings86against moving axially outwardly from its intended fixed position within the gap G. The bushings86can be formed of any desired material, including metal or plastic, with the selected material providing a reduced friction surface to facilitate the aforementioned relative torsional (rotational) and axial movement between the housing wall30and the retention member70. The bushings86can be provided to occupy the full gap G (slight interference to a line-to-line fit), or substantially the full gap G (substantially meaning that a slight gap of between about 0.0001-0.005 inches could remain). With the gap G being substantially reduced or eliminated, the bending stiffness between the lower housing28and the retention member70, and thus, between the respective first and second shafts40,66, is increased. The bending stiffness is further increased as a result of the resistance to bending, i.e. the interface between lower housing28and the retention member70, being spaced radially outwardly from the axis A along which a bending force would be generated. Accordingly, it will be recognized by one possessing ordinary skill in the art that the upper shaft subassembly24and the lower shaft subassembly26are able to rotate and translate relative to their common axis A along which first and second shafts14,16,40,66extend via flexing of resilient flex coupling42, as discussed above, while the lower housing wall30and the outer surface of the retention member70restrict bending between the upper shaft subassembly24and the lower shaft subassembly26, thereby restricting bending between the first and second shafts14,16,40,66.

While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. Accordingly, the invention is not to be seen as limited by the foregoing description.