Not Applicable.
Not Applicable.
1. Field of the Invention
This invention pertains generally to automotive suspension components that undergo large strokes and axle articulations during on and off road conditions, more particularly to rear radius arms that connect an automotive frame to a rear axle to improve vehicle handling characteristics when at or lifted above the factory design, and still more particularly to chassis modifications that allow for aftermarket addition of rear radius arms.
2. Description of Related Art
Off road vehicles have developed the capacity for large-excursion wheel movements both on and off road. Typically, off road performance is traded off against on road performance. In the past, such trade off was common.
Front radius arms were first implemented by Rubicon Manufacturing, Inc. in 1997. These front radius arms allowed for improved on and off road performance improvements, without detracting from either.
United States patent application US 2006/0033298, entitled “Vehicle Suspension with Improved Radius Arm to Axle Attachment” is hereby incorporated by reference in its entirety.
An aspect of the invention is a rear axle radius arm that comprises: a frame on one side of an automobile; and means for linking a rear axle to the frame. The means for linking the rear axle to the frame may comprise: a bracket attached to the frame; the frame comprising: a medial side closer to a front-to-back medial plane of substantial symmetry in the automobile; a distal side further away from the medial plane than the medial side; a bottom side; and a radius arm movably attached to the bracket mount, wherein the radius arm movably connects the rear axle to the bracket.
By substantial symmetry, it is meant that frame rails are functional mirror images of each other, the doors and body panels substantially mirror each other (depending on the design), and the wheels are disposed equidistantly from the plane of substantial symmetry. The plane of substantial symmetry would ideally intersect the center of gravity of the vehicle. For example, with a 2, 4, or 6 seating vehicle, the driver and front passenger are substantially equidistant from the vertical plane of substantial symmetry between them. For 3, 6, or 9 seated vehicles, the middle seat would intersect the plane of substantial symmetry. This all assumes that the seating for each row of seats are equal. A less precise, but perhaps more informative notion of the plane of substantial symmetry would be the vertical front-to-back “middle” plane that would separate the driver side of the vehicle from the (front seat) passenger side.
The means for linking the rear axle to the frame may comprise: a movable joint that connects to the frame; a first compliant pivot that attaches to a first mount on the rear axle; and a second compliant pivot that attaches to a second mount on the rear axle. An intermediate compliant pivot may be disposed between the movable joint and the second compliant pivot. Alternatively, a substantially noncompliant intermediate attachment point may be disposed between the movable joint and the second compliant pivot, wherein the first compliant pivot, the second compliant pivot, and the movable joint are rigidly connected by a substantially rigid connection (aside from temporary recoverable deformations due to torsion and bending). These temporary recoverable deformations are insufficient to permanently yield the material into a permanent deformation.
The bracket above may comprise: a doubler plate attached to a first side of a frame; a cuff attached to a lower side of the frame and through a second side of the frame opposing the first side of the frame to the doubler plate; and a control arm mount attached to the cuff, comprising a shaft wherein a movable link may be rotationally or spherically movably attached to the shaft. When so assembled, the doubler plate, cuff, and control mount are removably mounted to the frame in an extremely stiff manner. Additionally, this arrangement of the doubler plate and cuff acts to distribute loads placed on the frame from the control arm mount, and stiffens the frame where attached.
One or more of the upper compliant pivot, the intermediate compliant pivot, and the lower compliant pivots may allow for both rotational and tilt movements out of a plane of nominal rotation.
Another aspect of the invention is that the radius arm may comprise: (1) a lower control arm that comprises: a lower compliant pivot that connects to a lower mount on the rear axle at one end; a movable joint that connects to the bracket mount located on the frame at the other end; and (2) an upper control arm bracket located between the lower compliant pivot and the movable joint; and an upper control arm that comprises: an upper compliant pivot that connects to an upper mount on the rear axle at one end, and an intermediate compliant pivot that connects to the upper control arm bracket.
The rear axle radius arm may comprise one rear axle radius arm on each side of the medial plane of the automobile; and a center of rear suspension rotation, comprising a line drawn between the two brackets attached to the frame that substantially intersects a center of rotation of a double Cardan joint, wherein the double Cardan joint is connected at one end to a drive shaft that connects a differential, and at the other end to an output of a rotational power source. The rotational power source may comprise either a transfer case or a transmission.
The rear axle radius arms on each side of the medial plane may be substantially mirror images of each other.
The lower mount on the rear axle may previously have been attached to a factory installed rear lower control link. Similarly, the upper mount on the rear axle may previously have been attached to a factory installed rear upper control link.
The rear axle radius arm bracket may comprise: an aftermarket bracket attached to the frame. By aftermarket, it is meant that the bracket is generally not originally supplied by the original equipment manufacturer. The bracket may be attached to the distal side of the frame, the medial side of the frame, or the bottom side of the frame.
The bracket above may comprise a stamped locator that precisely locates the bracket by a factory frame precision reference locator.
Additionally, the bracket may be attached to the bottom side of the frame. In fact, it may be attached to the distal side, bottom side, and medial side of the frame, and may further curve to the top of the frame for additional support. The bracket may attach to the frame with components that comprise: (a) a cuff comprising a lower lip; (b) the bracket attached to the cuff; (c) a doubler plate; (d) wherein the radius arm attaches to the bracket; and (e) wherein the cuff bolts through the frame to the doubler plate; and (f) wherein the cuff lower lip attaches through the bottom side of the frame to a plate with retained fasteners.
The rear axle radius arm upper compliant pivot, the intermediate compliant pivot, and the lower compliant pivots may all allow for both rotational and translational movements, either rotational or translational movements, or no movement. Each of the upper compliant pivot, the intermediate compliant pivot, and the lower compliant pivots may comprise: a housing; a thick-walled tubular compliant bushing disposed within the housing; two caps that protrude into the inner diameter of the tubular compliant bushing that allow passage of a central shaft, wherein the housing and caps limit translational movement of the central shaft within the housing through limited deformation of the compliant bushing.
The vehicle stroke and articulation movements are possible with the rear axle relative to the vehicle frame. Stroke is allowed through rotation of the movable joint, where, if both radius arms simultaneously identically rotate, the rear axle moves up and down. Differential movements of the radius arms require axle articulation, which is accomplished through spherical motion of the movable joint, and through deformations in the compliant pivots that allow off-axis tilts of the pivots. A still further aspect of the invention is a method for retrofitting a rear axle connection to a frame with a set of two radius arms, the method for retrofitting each of the radius arms may comprise: providing a rear axle, the rear axle comprising: an upper control link mount and a lower control link mount, wherein both upper and lower control link mounts respectively connect to rear lower and rear upper control links that are in turn connected to the frame, such that the upper control link, the lower control link, the axle, and the frame form a moveable four-bar linkage wherein the axle moves relative to the frame; removing the upper control link and the lower control link; attaching a radius arm bracket mount to the frame on the distal side of the frame; installing a radius arm, the radius arm comprising: a lower radius control arm that spherically mounts to the frame bracket mount and the lower axle bracket mount; an upper radius arm that pivotally mounts to the upper radius arm bracket on the lower radius arm on one end, and pivotally attaches to the axle upper control link mount at the other end. In this manner a retrofitted vehicle may be built.
Another aspect of the invention may comprise: a frame on one side of an automobile, wherein: the automobile has a medial plane, and the frame has medial side closer to the medial plane, and a distal side further away from the medial plane than the medial side; and means for linking a rear axle to the frame.
The means for linking the rear axle to the distal side of the frame may comprise: a bracket mount located on the distal side of the frame; and a radius arm movably attached to the bracket mount, wherein the radius arm movably connects the rear axle to the bracket mount.
In still another aspect of the invention, a serviceable rear axle radius arm mount, may comprise: a vehicle chassis in a vehicle; and means for mounting two rear axle radius arms to the chassis. The means for mounting may further comprise: (a) a rear axle radius arm mount attached to the chassis; and (b) a separately removable section that may be separately removed from the rear axle radius arm mount; (c) wherein the rear axle radius arm has a substantially constant alignment both prior to and after removal of the separately removable section.
In another aspect, the serviceable rear axle radius arm mount may comprise: (a) two frames substantially bilaterally disposed about a medial plane of substantial vehicle symmetry; (b) two frame mounts bilaterally disposed about a separately removable section; (i) wherein each frame mount attaches to the vehicle chassis through one of the frames on one side, and to the separately removable section on the other side; (ii) wherein each frame mount has a pivot connection to a rear axle radius arm; and (c) each rear axle radius arm substantially radially connects the rear axle to the vehicle chassis.
In this aspect, removal of the separately removable section does not change the location or alignment of the rear axle radius arms, thus facilitating servicing by reducing removal and realignment time.
In another aspect of the invention, a serviceable transmission mount with front radius arm mounts may comprise: (a) a vehicle frame; (b) means for mounting two front radius arms, the means for mounting attached to the vehicle frame; and (c) means for supporting a transmission attached to the means for mounting the two front radius arms.
The means for supporting the transmission may be separately removable from the means for mounting the two front radius arms. Furthermore, the means for mounting the two front radius arms may comprise means for mounting two rear radius arms. In this instance, there may be a total of four radius arms mounted, and removal of the separately removable means for supporting the transmission does not affect the alignment of any of the radius arms or other suspension component.
The means for supporting the transmission may comprise: a structural member bolted to the transmission and removably bolted to the means for mounting the two front radius arms.
In still another aspect of the invention, the vehicle front end (that comprises front radius arms) remains in substantially identical front wheel alignment before removal and after replacement of the means for supporting the transmission.
Further aspects of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon.
The invention will be more fully understood by reference to the following drawings which are for illustrative purposes only:
Referring more specifically to the drawings, for illustrative purposes the present invention is embodied in the apparatus generally shown in
Lifting
In off road motorized sports, a frequent object is to be able to take a vehicle over increasingly rugged terrain. Even though factory off highway vehicles (OHVs) are designed and sold with some degree of off road capability, the aftermarket manufacturer is attempting to make the vehicle perform with higher capability off road, while retaining the comfort and handling characteristics of highway driving. Thus, the factory configuration of the vehicle chassis is perhaps not sufficiently high to clear particularly difficult rock climbing terrain, such as the Rubicon Trail.
The Rubicon trail is also known as the McKinney-Rubicon Springs Road, which is located in the California High Sierras due west of Lake Tahoe. This particular trail is rated as a “10” as being “most difficult” on a scale of 1-10. It is referred to as the “Granddaddy of all off highway trails” it is about. 12 miles of incredibly scenic but extremely challenging rocky road.
In order to successfully challenge such difficult trails, where rocks are strewn across the trail to heights of three feet or more, one attempts to raise the chassis of their OHV every little bit in order to gain more clearance. This process of raising the chassis (which is basically everything above the wheels) is referred to as “lifting”. “Ordinary” lifts are perhaps 2.5″ to 4″, with lifts exceeding 10″ not infrequent.
There are at least two major difficulties that accompany lifting: 1) vehicle handling deteriorates markedly, and 2) the factory designed drive train (everything from the transmission or transfer case to the axles) are sufficiently changed so as to engender excessive drive-train-induced vibrations as well as exceed the allowable design departure angles (angles of bend in the joint) of various U-joints, constant velocity joints, and the like.
One aspect of this invention seeks to ameliorate or eliminate the various limitations that result from the practice of lifting, whether done at a factory, or done as an aftermarket modification. This will be further described below.
Rear Axle Radius Arm
Refer now to
A bracket 108 is attached to the frame 104. The bracket 108 provides a rotational attachment point for the rear axle radius arm 102 through a movable joint 110, which may either be principally a rotational with a small amount of spherical compliance, or a more preferably a spherical joint that has at least a portion of its range of mobility capable of spherical rotation.
The frame 104 has a side closer to a front-to-back medial plane of substantial symmetry (not shown) in the vehicle (known as a medial side 112), a further away side (known as a distal side 114) from the medial plane than the medial side 112, a bottom side 116, and the radius arm 102 that is movably attached to the bracket 108, wherein the radius arm 102 movably connects the rear axle 106 to the bracket 108.
The rear axle radius arm 102 constrains movement of the rear axle 106 relative to the radius arm 102 through the movable joint 108 that connects to the frame 104, a first compliant pivot 118 (hereafter referred to for convenience as the upper compliant pivot 118 without loss of generality) that attaches to a first mount 120 (hereafter referred to for convenience as the upper mount 120 without loss of generality) on the rear axle 106, a second compliant pivot 122 (hereafter referred to for convenience as the lower compliant pivot 122 without loss of generality) that attaches to a second mount 124 (hereafter referred to for convenience as the lower mount 124 without loss of generality) on the rear axle 106; and an intermediate compliant pivot 126 disposed between the movable joint 110 and the second compliant pivot 122, where the pivot 126 attached to the lower control arm 128.
The movable joint 110 is preferably a spherical joint, allowing a spherical range of motion within a limited solid angle of motion for rear axle 106 strokes and articulation.
The upper 120 and lower 124 mount designations are merely used here as a convenience in referring to the drawings, as the upper and lower positions may be rotated about the rear axle 106 as design needs dictate, so long as the functionality of the radius arm 102 is not compromised. Thus, they may be move to less than opposing angles, be made parallel to the ground, or otherwise located. Additionally,
It should be pointed out in particular that these upper 120 and lower 124 mounts may in fact be factory mounts that originally were used for rear axle connection to other suspension components. Alternatively, the mounts may be generic to a specific rear axle build. Still another option would be that the rear axle mounts were specially fabricated for one of the rear radius links disclosed here. Regardless of the purpose or origin, the mounts may be used for attachment to some form of the rear radius arm disclosed herein.
Nowhere in this application is a limitation required where a mount serves only as a suspension mounting location for rear radius arms; they may additionally be mounts for shock absorbers, brake lines, or other components conveniently attached to a mount. The only restriction would be that the mount would allow movement of the rear radius arm within its envelope of operation without interference with other components.
The rear axle radius arm 102 may comprise: a lower control arm 128 that comprises: (1) a lower compliant pivot 122 that connects to a lower mount 124 on the rear axle 106 at one end; and (2) a movable joint 110 that connects to the bracket 108 located on the frame 104 at the other end; and (3) an upper control arm bracket 130 located between the lower compliant pivot 122 and the movable joint 110, on lower control arm 128; and an upper control arm 132 that comprises: (1) an upper compliant pivot 118 that connects to an upper mount 120 on the rear axle 106 at one end, and (2) an intermediate compliant pivot 126 that connects to the lower control arm 128 at the upper control arm bracket 130.
The lower control arm 128 may have a lower control arm length adjustment 134. Similarly, the upper control arm 132 may have an upper control arm length adjustment 136. These length adjustments are made to correctly position the rear axle 106 to a specific location and angle of inclination relative to the frame 104, as well as a position the rear axle 106 substantially orthogonally to a vertical plane that passes through the front-to-back medial plane of substantial symmetry (not shown) in the vehicle. The rear axle 106 may additionally be correctly positioned relative to a drive shaft and rotational power source, as further described below.
The rear axle radius arm 102 may be disposed as one rear axle radius arm 102 on each side of the medial plane of the automobile. A line may be drawn between the centers of the two rear axle radius arms 102 movable joints 110 to form a center of rear suspension rotation. The rear axle radius arms 102 disposed as above on each side of the medial plane may be substantially mirror images of each other, or may otherwise be identical, depending on the application. This center of rear suspension rotation may alternatively be drawn between the two brackets 108 attached to the frame 104.
An even simpler implementation occurs when the rear axle 106 is just a free wheeling (i.e. undriven) rear axle 106 in a front wheel drive vehicle, in which case there is no differential, and no drive shaft connection to the rear axle 106.
Refer now to
In
In
One implementation of the sliding upper control arm is shown in inset 142, where a threaded portion 144 allows for an initial length adjustment, and a spline 146 slides into a receiving spline 148, surrounded by a helical or other type spring 150. The sliding action of the spline 146 allows for axle stroke
In all of the rear axle radius arm implementations of
Refer now to
Referring back to
Comparing
Refer now to
However, even if the rotational velocity of the pinion 304 relative to the output shaft 314 is constant, the drive shaft 306, of non-negligible rotational inertia, will undergo sinusoidally varying rotational rates during every revolution simply as a consequence of the rotational linkage between two U-joints. To a person occupying the vehicle driven by the drive shaft 306, this is experienced as a drive shaft 306 induced vibration. This induced vibration is typically managed by replacing U-joints 310 and 312 with constant velocity joints (CV-joints).
Further, in
When the double U-joint has differing angles of declination and inclination, a sinusoidal surging through each revolution is transmitted to the rear axle 106. This is another reason that the auto industry has adopted the utilization of constant velocity (CV) joints instead of the U-joints of former years.
Even traditional CV joints have difficulties with accommodating the geometries of an OHV, where the drive train may experience extreme angle changes that bend into a very acute geometry. Even when CV-joints replace the U-joints 310 and 312, disparate inclination and declination angles cause phasing errors that result in surging vibrations originating in the drive shaft 306 and rear axle 106. One solution to this is described below.
Refer now to
Refer now to
The compliant pivots 500 may each comprise: a housing 502; a thick-walled tubular compliant bushing 504 assembled and disposed within the housing 502; two metal caps 506 that protrude into the inner diameter 508 of the tubular compliant bushing 504 that allows for a passage of a central shaft 510 into a nut 512, wherein the housing 502 and caps 506 limit translational movement of the central shaft 510 within the housing 502 through constrained deformation of the tubular compliant bushing 504.
The thick-walled tubular compliant bushing 504 may be comprised of a compliant material, such as a 75 durometer nitrile-butadiene rubber (NBR) or other such compliant material. Each of the bushings may have a different size and durometer, as optimized by vehicle dynamic modeling codes, as well as actual on and off road performance testing.
A first example of the underbody of a first representative off road vehicle is modified in
Refer now to
The cross member 602 traditionally provides support to the transmission 604. The cross member 602 is suitable for aftermarket modifications as explained further below.
In the factory configuration, the rear axle 106 is supported by the rear lower control arm 202 and the rear upper control arm 206 that both medially attach to the frame 104.
Refer now to
Also shown in
Refer now to
Removal of the central section 616 may allow access to other underbody components that may otherwise be quite inaccessible.
A second example of the underbody of a second representative off road vehicle is modified in
Refer now to
The cross member shield 702 traditionally provides support to the transmission 704. The cross member 702 is suitable for aftermarket modifications as explained further below.
In the factory configuration, the rear axle 106 is supported by the rear lower control arm 202 and the rear upper control arm 206 that both medially attach to the frame 104.
Refer now to
Referring again to
The first lateral support 708 comprises a first pivot mount 714 that provides a pivotal support to the rear axle radius arm 102. The first pivot mount 714 may either be an integral component of the first lateral support 708, or may be removably attached. Similarly, the second pivot mount 716 may either be an integral component of the second lateral support 712, or may be removably attached. Generally, both pivot mounts would be either integral or attached, but would unlikely be one of each.
The removable center section 710 may be detached from the first lateral support 708 and the second lateral support 712, and may also support either a transmission 704 or transfer case 308. When servicing of the transfer case 308, or other supported component (not shown), the transfer case 308 may be removed along with the removable center section 710. It should be noted that removal and replacement of the removable center section 710 and transfer case 308 does not require realignment of the rear axle radius arms 102.
The removability of the center support section 710 allows for the servicing of driveline components (transmission 704 or transfer case 308) without the additional labor required to remove and replace the rear axle radius arms 102, followed by an entire rear end alignment due to suspension dimensional changes in the mounting of the rear axle radius arms 102.
The aftermarket transmission and radius arm mount 706 (comprised of the first lateral support 708, the center support 710, and the second lateral support 712) may additionally have strengthening gussets (not shown for clarity, but in reality such gussets could be both in front and back of the radius arm mounts, and on both driver and passenger sides of the vehicle) that increase the overall strength of the aftermarket transmission and front radius arm mount 706, stiffen the vehicle frame 104, and additionally provide an extremely rugged shield for rock scraping in challenging off road rock climbing and bouldering activities.
Similar to the mounting locations 716 for the rear radius arms 102, there may be front radius arm mounts 718 for mounting of front radius arms 720. Again, removal of the removable center section 710 allows for work to be done beneath the center section 710 without consequent realignment of the rear axle radius arms 102 or front radius arms 720.
The aftermarket transmission and radius arm mount 706 is useful even when the frame 104 is accessible for mounting the rear axle radius arms 102, because the mount and shield allows for the rear axle radius arm 102 mounts 714 and 716 to be shifted significantly forward. In vehicle handling characteristics, even a one or two inch shift forward lengthens the effective wheel base of the rear axle, in many cases dramatically improving handling characteristics. Here, the mount and shield may be moved far forward. The resultant dual radius arms and transmission mount would allow for frame 104 stiffening, as well as the opportunity for very long radius arm lengths.
Refer now to
Removal of the central section 710 may allow access to other underbody components that may otherwise be quite inaccessible.
Refer now to
A precision semi-pierced geometric feature 810 aligns with matching precision points on the frame 104 (again not shown), and will vary in geometry depending on the geometry of the precision points on the frame 104. A lower lip 812 folds under the cuff 802 to better distribute loads to the frame 104 without undue concentrations of stress leading to premature fatigue and breakage of either the frame 104 or the mount 800.
A doubler plate 814 additionally assists in mounting to the frame 104. Another semi-pierced precision feature 816 allows for precise locating of the doubler plate 814. Both this feature 816 and the previously discussed feature 810 may either be in fact semi-pierced, or may be completely punched, and replaced and welded into a semi-pierced position. Such a weld semi-pierced feature is in fact much stronger than a strictly punched semi-pierced feature, and results in a much more reliable feature.
A plurality of high strength carriage bolts 818 pass through the double plate 814, into a cylindrical spacer 820, through the cuff 802, and into a lock washer 822 and finally a nut 824. The cylindrical spacer 820 may either be treaded to engage the bolt 818, or may permit passage of the bolt 818 without treaded engagement.
Additional flat head screws 826 are countersunk into the lower lip 812, and pass through the lower lip 812, through a clearance hole in the frame 104, and are secured by a plate 828 that has PEM or other such fasteners 830 attached thereto. As the plate 828 is fixed into place within the hollow rectangular beam that comprises the frame 104, it is passed from a convenient place outside the frame, and pulled into position so as to align with the plurality of flat head screws 826. This may be simply accomplished by bending a piece of wire to pass within the threaded diameter of the fastener 830.
Additional flat head screws 832 pass through the doubler plate 814 to be threaded into cylindrical spacer 834, which in this case is threaded to receive the flat head screws 832. On the other side of the cylindrical spacer 834, another set of flat head screws 836 pass through the cuff 802, through a clearance hole in the frame 104, and finally threads into the cylindrical spacer 834.
Refer now to
This view more clearly points out the radius arm bracket 108, which is welded to the cuff 802. Radius arm pivot bolt 808 is seen to pass through the bracket 108, and secures onto the welded nut 804 (shown here in dashes, as it is hidden in this view).
All components of the bracket 108, cuff 802, and doubler plate 814, and miscellaneous hardware are steel or other high-strength material, suitable for the loads being placed upon them by the radius arm (not shown), as applied through the radius arm pivot bolt 808.
Lower Control Arm Section of Rear Radius Arm
Refer now to
An intermediate compliant pivot mount 910 is placed along the body 908, with bends 912 and 914 occurring as necessary to avoid other factory parts during the designed stroke and articulation of the rear axle 106 (not shown here).
Finally, at the terminal end of the control arm body 908, the lower compliant pivot housing 916 is placed.
Although the control arm body 908 is shown as tubular, it may be any suitable cross section, and may even be pieced together with one or more differing cross sections.
The treaded shaft 906 allows for lengthening or shortening the overall distance between the centers of the movable joint 110 and lower compliant pivot housing 916
Radius Arm Partial Spherical Pivot Refer now to
First, a clip ring 918 is placed into a land (not shown) in the spherical housing 920 from one side of the spherical housing 920. Following the clip ring 918 installation, the following components are installed as a stacked from the side opposite that of the clip ring 918: a retention washer 922, a first spherical race 924, a partial spherical bearing 926 (partial due only limited range of motion in a spherical sense), a second spherical race 928 (that may be identical to the first spherical race 924), and finally a threaded adjustment retainer 930. When assembled as indicated, the inner diameters of the retention washer 922 and threaded adjustment retainer 930 place a limit the amount of spherical motion allowed to the spherical bearing 926. Any pivot shaft (not shown) passing through and attaching the partially spherical bearing 926 would also tend to limit the amount of spherical motion allowed by the rear axle radius arm (102 in
Further Chassis and Assembly Drawings
Refer now to
For instance,
Here, the rear axle 106 connects to the rear radius arm 102 through the upper compliant pivot 118 and the lower compliant pivot 122. The upper compliant pivot 118 and the intermediate compliant pivot 126 connect with a length adjustment 136. Continuing up the control arm body 908, a threaded section 906 threads into a bolt 904 welded to a neck 902 where a movable joint 110 mounts to the bracket 108. As may be seen from the drawing, bracket 108 mounts to the distal side 114 (outside) of the frame 104.
As stated previously movable joint 110 allows for rotational and some limited degree of spherical compliance, as so the upper compliant pivot 118, the lower complaint pivot 122, and the intermediate compliant pivot 126. The compliances of these various pivots allow for purely rotational movements at the pivots so that the axle 106 may move through a radial arc centered about the movable joint 110.
Additionally, due to the compliant nature of the upper compliant pivot 118, the lower complaint pivot 122, and the intermediate compliant pivot 126, as well as the partially spherical nature of the movable joint 110, now the rear axle 106 may twist, so that one side of the axle is closer to the frame than the other. Such twisting action is known as articulation. In the absence of the compliant pivots, such articulation is not possible, and the rear axle, rear axle radius arm, and the frame would allow only a single degree of freedom rotation about movable joint 110, and no articulation would be possible.
Refer now to
When vehicles are raised beyond their factory or stock ride height (otherwise known as ‘lifted’), handling typically deteriorates, and driveline components suffer due to lifted operation outside of their design envelopes. The radius arm geometries disclosed here improves the handling of ‘lifted’ vehicles by reducing the chassis-induced roll-oversteer. The rear axle radius arm design is a departure from the factory geometry in two ways.
First, the rear axle radius arm is significantly longer than the stock configuration, which has the effect of reducing the change in wheelbase that occurs throughout the range of motion. The axle movement causes the change in wheelbase as the axle is constrained by the control arms. As the control arms become longer, the radius of the suspension stroke becomes larger, and the result is a reduced horizontal component within the vertical range of motion (commonly called suspension stroke). Changes in the horizontal component of the suspension stroke cause the vehicles wheelbase (distance between front and rear wheels) to change which results in a secondary turning component. The most common time to feel the effects of this secondary turning component are when intentionally turning the vehicle. The driver will turn the steering wheel an amount necessary to initiate a constant radius turn. The vehicle body will roll in relation to the suspension system as a result of centrifugal force. The compressed side of the vehicles suspension will increase the wheelbase on that side only, while the unloaded suspension will reduce the wheelbase on the opposite side of the vehicle. The result of this wheelbase asymmetry is a turning force that requires the driver to reduce the initial steering input in order to realize the turning radius that was originally input by the steering wheel. This effect is called chassis induced roll oversteer.
Secondly, the rear axle radius arms have a single point of frame attachment, instead of the relatively shorter factory four bar linkage, which reduces unwanted rear axle steer, relative to the suspension stroke. These two attributes work together to improve the handling of the lifted vehicle. The rear radius arm disclosed here accomplishes these handling improvements with a unique design that captures four mounting points (upper and lower on both sides) of the stock axle that were designed for the factory four bar linkage design, and adds another compliant bushing in the rear axle radius arm itself to provide the necessary movement in what would otherwise be a fully constrained rear axle suspension design. The use of this additional bushing is a design unique to this invention and is another reason why these rear axle radius arms improve vehicle handling so well.
Although the description above contains many details, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for.”
This application claims benefit of priority to U.S. provisional patent application Ser. No. 60/979,747 filed Oct. 12, 2007, hereby incorporated by reference in its entirety, U.S. provisional patent application Ser. No. 60/982,423 filed on Oct. 25, 2007, incorporated herein by reference in its entirety, U.S. provisional patent application 60/982,987 filed on Oct. 26, 2007, incorporated herein by reference in its entirety, and U.S. provisional patent application Ser. No. 60/983,152 filed Oct. 26, 2007, incorporated herein by reference in its entirety.
Number | Date | Country | |
---|---|---|---|
60979747 | Oct 2007 | US | |
60982423 | Oct 2007 | US | |
60982987 | Oct 2007 | US | |
60983152 | Oct 2007 | US |