CA1192919A

CA1192919A - Vehicle wheel suspension

Info

Publication number: CA1192919A
Application number: CA000407979A
Authority: CA
Inventors: Bernard J. Finn; Ming-Chih Yew
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1981-12-21
Filing date: 1982-07-23
Publication date: 1985-09-03
Also published as: GB2111922A; GB2111922B; JPS58112814A

Abstract

VEHICLE WHEEL SUSPENSION
Abstract of the Disclosure A vehicle wheel suspension includes trans-verse control arms for an opposed pair of road wheels and a primary suspension spring beam spaced longitudinally of the vehicle away from the control arms and interconnected therewith by torsion rods installed on axes located outboard of the swing axes of the transverse control arms.

Description

D-5,235 C-3369 VEHICLE WHEEL SUSPENSION
This invention relates to vehicle wheel suspensions and more particularly to such suspen-sions employing transversely oriented primary sus-pension spring beams.
The installation of a total drive aggre-gate in either a front or rear compartment of the modern vehicle, combined with the general trend to-ward reduction of volume and mass in those areas of the vehicle body, imposes substantial design limitations in the use o-f conventional chassis systems, particularly vehicle suspension elements.
Space and structure formerly available for locating such items as suspension control arms, vertical shock struts, coil springs and the like is needed for drive train components. Moreover, modern com-bined spring and shock strut suspensions of the so-called MacPherson type provide no completely satis-factory answer since they dictate high hood and quarter profiles resulting from the vertical stack-ing of the suspension elements typical in those arrangements.
The present invention provides vehicle wheel suspension affording greater latitude to the vehicle designer in both space utilization and body styling. It includes a pair of transversely ori-ented contro~ arms for the opposed road wheels and adapted to swing about longitudinal axes of the sprung mass in conventional manner. However, rather than connecting with such control arms a primary suspension coil or like spring at each side in the vicinity of each road wheel, such primary ~9~

suspension spring rather is comprised of a trans-verse elastic beam spaced longitudinally from the control arms and which may be in an area of the vehicle not required for other components. Substan-tial space is thus freed laterally between the con-trol arms such as for drive aggregate, as well as the space near and above the road wheels normally consumed by compressible coil springs on MacPherson struts or otherwise.
Such a longitu~i n~l ly spaced transverse primary suspension spring has been proposed on paper in the past but appears commercially unsatis-factory. Thus, Grosseau 3,701~542 and 3,831,966 show a suspension arrangement including a trans-verse primary spring beam, conventional quadri-lateral suspension linkage, and torsion bars extend-ing from the lower quadrilateral arms along their pivot axes to connect such control arms with the ends oE the suspension spring. Such an arrangement necessitates that the bending modes of the trans verse spring caused by normal vehicle ride and handling deflections of the road wheels can be accommodated only by specially proposed connecting systems between the ends of the transverse spring and the two torsion bars. Such proposals form the subject of the pa-tents and are clearly unsatis-factory from several functional and structural standpoints.
By the present invention a commercially superior arrangement of a transverse spring suspen-sion is provided. It has been found in the course of developing our invention that reinorced poly-meric material such as fiberglass filled polyester resin or the like exhibits superior properties Ior use in a spring beam. The present arrangement o~
the transverse spring beam makes effective use of a beam made of such material not only as the primary suspension spring but also as the principal or only anti-roll element for control of vehicle handling characteristics. We provide a practical arrange-ment which not only avoids elaborate prior art interconnection devices between the deflecting wheel control arms and the suspension beam but also eliminating functional deficiencies of the prior art.
Thus, the invention features the use of interconnection elements, such as torsion bars, which are simply fixed each at one end to a control arm and aligned along longitudinal axes of the chassis spaced outboard of the control arm pivot axes, and then simply fixed at their other ends to the transverse beam terminal ends in such fash-ion that control arm deflections cause the trans-verse beam to experience bending modes which arecharacterized by an inboard pair of nodal points within the beam at fixed locations o~ the sprung mass. ~his nodal point bending characteristic at once affords and is the result of the simple con-nections just described. With the Grosseau struc-tures, the interconnections at the ends of the transverse beam, while elaborate, still experience gross amounts of relative sliding motion between the beam ends and the interconnecting element as beam deflection occurs, and the torsion rods are loaded in bending modes as well as torsionally.
~ith the instant invention, the nodal point bending characteristic enables geometry wherein no apprec-iable such relative displacement will occur. ~nd, should long rods be chosen as an interconnecting element, as is true in the instant preferred embodi-ment, then further advantage is derived from the fact that no longitudinal bending of the torsion rod occurs and there need be no independent structural support of such rod on the chassis sprung mass as required in the prior art.
~ ore specifically, the nodal point beam bending characteristic of the present invention contemplates that the spacing between the control arm axis and the torsion rod axis may be so selected with reference to the material properties of the beam and the torsion rod, if such be used, that both the beam end and the control arm anchorages of the torsion rod ends describe generally identical arcu-ate paths in parallel planes in space during wheel de1ections. The torsion rod, or other intercon-necting device, acts to simply carry a pure force couple between the control arm and the respective beam end. To complete the system, reaction load elements are proyided on the chassis sprung mass at the nodal points of the beam to serve as spring con-straints during vehicle roll. The entire such sys-tem enables use of the lightweight polymeric spring above referred to as the sole or principal ride and anti-roll rate control element, and without any undue sacrifice in one function to favor the other.
We expect further advantage herein in that by judicious design of such nodal point reaction ele-ments, even expanded latitude will be afforded thedesigner in selection of the ride and the anti-roll behavior of the spring beam and -thus of the vehicle.
Employing all of the aforementioned realized ob~ectives and features of this invention results in a suspension package of light weight, high space utilization efficiency and simplicity of construction. The spring beam is even easily contained within a relatively shallow box section cross member of the vehicle where the spring is at a low position giving space for engine aggrega-tes yet is protected from road hazards. The suspen-sion may additionally feature design height adjust-ment provisions wherein the torsion rods of the exemplary embodiment are connected to the respective control arms via adjustable lever arm devices suit-able to variable prestressing of the torsion rod and spring beam to support the vehicle mass at variable design heights.
The foregoing objects, features and advan tages of the invention will be readily apparent from the following specification and from the drawings wherein:
Figure 1 is a fragmentary, perspective view, partially in phantom, of a vehicle chassis sprung mass and wheel suspension therefor in accordance with the invention;
Figure 2 is an enlarged elevational view, partially in section, taken generally along the plane indicated by lines 2-2 of Figure 1 and indi-cating the wheel suspension in a plurality of wheel positions;
Figure 3 is a reduced sectional view taken generally along the plane indicated by lines 3-3 of Figure 2;
Figure 4 is a similar view taken generally along the plane indicated by lines 4-4 of Figure 3;
and Figures 5 through 7 are diagrammatic

2~

representations of various bending modes of the spring beam of the suspension.
Referring particularly now -to Figure 1 of the drawings, the same illustrates the front portion of an automotive vehicle chassis and front suspension r in accordance with this invention, for the steerable front road wheels as indicated in phantom at 10. Such road wheel is adapted for connection via a drive shaft assembly 12 to a front drive aggregate which may be located in the front compartment of the vehicle body or sprung mass, all as well known in the art. The present invention is directed to the packaging and body styling challenges arising with such front-drive design but it should be noted that this invention is equally well adapted to vehicles with rear drive aggregates or otherwise where space utilization efficiency is a problem.
In the front drive vehicle shown, the vehicle sprung mass or chassis/body may comprise a drive aggregate cradle 1~ including a preassembled combination of stamped sheet metal welded box sec-tion rails 16 and fore and a~t spaced box section cross members only generally indicated at 18 and 20. Such cradle assemblies support the vehicle drive aggregate, not shown, and are conventionally bolted to the remainder of the vehicle body via isolation mounts.
~ vehicle wheel suspension in accordance with this invention is, in the instant preferred embodiment, structured to include members presently found in ver-tical strut/shock suspensions but it should be understood that the principles of the invention are not thus limited. A vertical strut/
shock 22 comprises an outer shock cylinder 24 and a telescoping piston rod 26 suitably anchored to an upper sheet metal tower structure 28 of the vehicle body sprung mass, as via a conventional isolation coupling indicated at 30 in Figure 2. As well known, such strut/shock 22 may further include a saddle bracXet 32 welded or otherwise fixed to cylinder 24 and including ears for reception o-E a spaced pair of through-bolt and nut assemblies 34 which attach the strut/shock 22 to an upper portion of the usual wheel support or knuckle 36. As is known, such knuckle, in the case of driven or live axle road wheels, includes provision for passage of the drive shaft 12 through the knuckle as a live spindle as here shown. The space utilization ad-vantages of the invention, while generally directed to the problems of drive aggregate packaging, may equally apply to dead spindle suspensions remote from the drive aggregate, or to older forms of propeller shaft rear drive vehicles.
The suspension of this invention includes for wheel 10 a transverse control arm 38 swingably mounted on the vehicle chassis sprung mass, as at rail 16. The control arm is thus mounted to swing on an axis A, at the center of an aligned pair of pivot assemblies which may be conventionally struc-tured of rubber bushed sleeves 40 seated in spaced legs of the control arm and affixed to bracke-ts 42 of the rail 16 via bolt/nut fasteners 44, Figures 3 and 4. At the outboard end of such control arm 38 there is provided a conventional ball joint 46 in-stalled within a lower portion of knuckle 36. ~s is known, such ball joint cooperates with strut/

shock 22 to define a steer axis for steerable road wheel 10 under actuation of conventional steering linkage, not shown.
Referring again to Figure 1, in accord-ance with the principles of the invention, thereis provided a transverse spring beam ~8. The spring is contained within the confines of the front box section cross member 20 and extends com-pletely therethrough to have symmetry about the vehicle centerline and identical connection with the opposite steerable road wheel 10 in the same manner as to that now to be described ~or the road wheel 10 shown. Thus, the descriptions given above and hereinafter to the structure illustrated are identically applicable to the other mirror half of the instant suspension embodiment. As to beam ~8, while the invention is in no way limited to a selection of spring material it has nevertheless been found that the invention is best embodied with a beam constructed of reinforced polymeric material such as a fiberglass reinforced polyester resin.
Such a spring beam achieves light weight while still absorbing high amounts of strain energy, and exhibits a modulus of elasticity well adapted to use for both ride and vehicle roll rate control as applied in the manner now to be described.
As seen in Figures 2 through 4, the spriny beam 48, in accordance with this invention, is arranged to have its terminal ends extend substan-tially laterally beyond vertical planes B containingthe swing axes A of the opposite control arms 3a.
In the instant e~bodiment, control arms 38 are con-nected to those extended ends of spring beam 48 by a pair of torsion rods 50. The torsion rods each ~2g~

- ~ -lie along an axis C, Figures 3 and 4, which lie outboard of the swing axes A of the control arms.
Each terminal end o~ the spring beam 48, indicated by the numeral 52, carries a clamp assembly 54 com-prised of mated upper and lower sections envelopingthe end of the beam and joined by fasteners 56 extending through apertures in the beam end 52, and further fasteners 58. A rubber or like material isolation sleeve 60 intervenes beam end 52 and the clamp assembly. The upper part of the clamp assembly includes a boss 62 suitably aper-tured and provided therein with internal splines mated with external splines on the forward ends of torsion rods 50, thereby to establish torque-carrying connection of each torsion rod to thespring beam 48 at axis C.
At its other end, the torsion rod carries similar external splines and is received within a design height adjustmeni device for control arm 38.
Such device comprises an elongated tubular lever member 64 having its rearward end rotatably carried within a pocket of the control arm as shown in Figures 3 and 4. The lever member has an arm or crank portion 66 extending transversely toward the ball joint 46. As seen best in Figure 2, the end of such crank portion is apertured and threaded to receive the threaded shank of a design height adjusting stud 68 which projects through an aper-ture of the control arm 38 and rests upon a beveled bolt head seat 70 fixed thereon. Thus, the torsion rods 50 are placed in torque-carrying relationship bet~een the control arms, which swing about axes A, and the elastic spring beam 48. As seen in Figure 5, with the front end weight of the vehicle sprung _g_ mass imposed in shares W/2 upon the bushings 40 at each axis A, the ground reaction W/2 on each road wheel lO creates a force couple M within each con-trol arm 38 representative of vehicle weight only, and tending toward counterclockwise rotation of the control arm viewed in Figure 2. Such force couple M is carried via the torsion rods 50 at axes C to the beam ends 52 thereby to cause the beam 48 to be stressed and deflected in accordance with its modu-lus of elasticity and torsion rods 50 are torsion-ally deflected in accordance with their elasticity.
The result is a specific angular position of con-trol arm 38 defining a so-called "design height"
for a particular sprun~ mass at so-called "design loading", e.g., 2 passengers and a quantity of cargo. The lever member 64 provides a convenient adjustment of the position of each control arm 38 about swing axis ~ in the presence of such deflec-tions under the weight of that particular sprung mass. The design height of the latter is simp~y adjusted by threaded rotation of stud 68 to vary the angular relationship of the contro:L arm, and thus the sprung mass, in relation to the crank por-tion 66 of the loaded torsion rod 50.
The result of the interassociation of parts thus far described is to cause spring beam 48 to have defined therein a spaced pair o~ neutral or nodal deflection points as at axis D, Figures 1, 2 and 4. Thus, as viewed in Figure 2, dynamic road forces causing deflection of road wheel lO in an upward direction to the broken line position shown, causes the torsion rod to impose an increased force couple at terminal beam end 52 in such a manner as g~

to bend the spring beam to a condition such as indi-cated at 48'. This bending occurs with the beam r~m~;nlng essentially vibratorily undisturbed in space or relative to the sprung mass cross member 20 at the location of nodal axes D~ Such is also true for an opposite deflection of the road wheel 10 and deflection of spring beam 48 to a position as indicated at 48" in Figure 2. This beam bending nodal point characteristic is true whether the opposite front road wheels 10 are de1ected in the same direction, as during pure ride motion, or dur-ing a turning maneuver where a roll couple imposes forces producing opposite wheel deflections across the car. As seen in Figure 6, in the former case of pure ride motion, the beam is in "pure bending"
as the term is known, i.e. equal force couples ~M
alone acting counter-rotatiVely on the beam ends, and with no vertical reaction forces required to hold the beam fixed in space or relative the sprung mass. As seen in Figure 7, during roll motion, the bending is converted to some higher order sinuous curvature to accommodate within the beam the situation where the force couples are of the same sense tend-ing to displace the beam bodily in space relative the sprung mass. In such case vertical reaction forces F are required in space and the same are provided characteristically of this invention by appropriate spring reaction mounts, to be described, located at the spaced pair of nodal points at

3~ axes D. A variety of dynamic road force conditions may of course be induced in the suspension combin-ing some part of each of the two theoretically pure cases shown in Figures 6 and 7, but the beam ~ is expected to bend about its characteristic nodal points at axes D in any case.
It is a feature of such beam bending characteristic in any of these cases that all such bending may proceed with no significant relative motion between the beam ends 52 and the respective control arm 38 at either side of the vehicle.
Thus, as viewed in Figure 2, the point on control arm 38 in some transverse vertical plane there-through wherein torsion rod 50 is centered candescribe virtually the same arc of travel as will the point on the beam end 52 o~ the spring beam in a parallel transverse vertical plane therethrough where the other end of torsion rod 50 is centered.
These are identified by the single arc C at each beam end appearing in Figures 6 and 7. The curved paths of the beam ends 52 are essentially de-scribed around the nodal axes D, while the circu-lar arcs of travel of the rearward end of the tor sion rod 50 are of course described about axes A of the bushings 40. Some minute difference in curva-ture may exist, but by appropriate selection of theelasticity of the torsion rods and of spring beam 48, these paths in the two spaced transverse planes may be essentially such that there need be no bend-ing forces of any importance longitudinally along axes C in the torsion rods 50. Such torsion rods thus simply carry the pure force couples associated with deflections of road wheels 10 about axes ~.
There need be no independent support of -the torsion rods on the sprung mass. And the location of tor-sion rods 50 away from axes A inherently simplifies the construction of control arms 38 and the bushings 40 over prior practice, where -torsion rods are placed directly on such axes A and the control arm pivots must accordingly be specially modified.
As seen best in Figure 2, the reaction mounts at axes D for the system are indicated at 7~ and each simply comprises an opposed pair of rubber or like material tapered blocks lightly force fitted between interior surfaces of cross member 18 and beam 48. The hardness of the rubber is selected to best achieve isolation of road dis-turbances from the ~ehicle sprung mass without significantly softening within the free-body force situations represented in Figure 7, the vertical restraint of noda~ axes D under forces F. It is expected, however, that the shape of the blocks, or the material softness thereof, or some appropri-ate combination of selections thereof may very well prove to impart further advantage to the instant invention in allowing yet another area o~
design flexibility wherein the roll rate of the suspension, for example, might be readily adjusted without affecting ride rate, simply by alterations in the behavior of spring beam 48 at its nodal points.
Of course, due to the lateral.spa~ing between rotational axes,so to speak,of the terminal beam ends 52 at D and the control arms at A, there is a consequent mismatch of the angular deflection which the two ends of torsion rod 50 undergo during wheel deflection. Such mismatch induces torsional deflection in such rods 50 during the wheel deflec-tion and gives rise to the consideration of the material of the torsion rod, also for appropriate design of the ride and roll characteristic of the suspension system. As indicated hereinabove, the invention is however not limited to the use of actual such torsion rods inasmuch as other means, such as longitudinal extensions of stamped metal from control arms 38, for example, may provide acceptable results. A varie-ty oE concerns such as cost, weight, the desired location o~ the trans-verse spring beam longitudinally apart from the control arms for efficient space utilization, etc.
will all enter in makins such choices. It is mani-fest, that the principles of the invention give rise to a number of such possibilities enabling practical suspension constructions of the instant general type not heretofore available.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Wheel suspension for the sprung mass of a vehicle which includes a transversely opposite pair of road wheels, comprising, a pair of trans-verse control arms each carrying one of said wheels and swingably mounted at one side of the sprung mass on a generally longitudinally extending axis thereof, a primary suspension spring comprising an elastic beam extending transversely of the sprung mass proximate said control arms but spaced longi-tudinally of the sprung mass therefrom and having end portions projecting outboard of generally verti-cal planes containing the swing axes of said control arms, means interconnecting each control arm to a respective end portion of said beam at a location on the latter outboard the respective said vertical plane and operative to carry to said beam forces de-flecting said control arms relative the sprung mass, whereby the beam is adapted to bend under such forces about a spaced pair of nodal points located substantially inboard of said interconnection loca-tions, and reaction mount means on the sprung mass engaged with said beam at said nodal points thereof.

2. Wheel suspension for the sprung mass of a vehicle which includes a transversely opposite pair of road wheels, comprising, a pair of trans-verse control arms each carrying one of said wheels and swingably mounted at one side of the sprung mass on a generally longitudinally extending axis thereof, a primary suspension spring comprising an elastic beam extending transversely of the sprung mass proximate said control arms but spaced longi-tudinally of the sprung mass therefrom and having end portions projecting outboard of generally verti-cal planes containing the swing axes of said control arms, a pair of torsion rods extending on axes gen-erally parallel but outboard said control arms swing axes and each connected at one end to a respective control arm and affixed at the other to an end of said beam, said rods being operative to carry to said beam forces deflecting said control arms rela-tive the sprung mass, whereby the beam is adapted to bend under such forces about a spaced pair of nodal points located substantially inboard of said interconnection locations, and reaction mount means on the sprung mass engaged with said beam at said nodal points thereof.

3. Wheel suspension for the sprung mass of a vehicle which includes a transversely opposite pair of road wheels, comprising, a pair of trans-verse control arms each carrying one of said wheels and swingably mounted at one side of the sprung mass on a generally longitudinally extending axis thereof, a primary suspension spring comprising a beam of elastic polymeric material extending trans-versely of the sprung mass proximate said control arms but spaced longitudinally of the sprung mass therefrom and having end portions projecting out-board of generally vertical planes containing the swing axes of said control arms, torsionally elastic means interconnecting each control arm to a respective end portion of said beam at a location on the latter outboard the respective said vertical plane and operative to carry to said beam forces deflecting said control arms relative the sprung mass, whereby the beam is adapted to bend under such forces about a spaced pair of nodal points each located substantially inboard of said interconnection locations, and reaction mount means on the sprung mass engaged with said beam at said nodal points thereof.

4. Wheel suspension for the sprung mass of a vehicle which includes a transversely opposite pair of road wheels, comprising, a pair of trans-verse control arms each carrying one of said wheels and swingably mounted at one side of the sprung mass on a generally longitudinally extending axis thereof, a primary suspension spring comprising an elastic beam extending transversely of the sprung mass approximate said control arms but spaced longitudinally of the sprung mass therefrom, and having end portions projecting outboard of generally vertical planes containing the swing axes of said control arms, a pair of torsion rods extending on axes generally parallel but outboard said control arm swing axes and each adapted for connection at one end to a respective control arm and affixed at the other to an end of said beam, sprung mass height adjustment means adjustably connecting said one end of each said torsion rod to a respective control arm, said rods being operative to carry to said beam forces deflecting said control arms relative the sprung mass, whereby the beam is adapted to bend under such forces about a spaced pair of nodal points located substantially inboard of said interconnection locations, and reaction mount means on the sprung mass engaged with said beam at said nodal points thereof.

5. Wheel suspension for the sprung mass of a vehicle which includes a transversely opposite pair of road wheels and a frame cross-member spaced longitudinally therefrom, comprising, a pair of transverse control arms each carrying one of said wheels and swingably mounted at one side of the sprung mass on a generally longitudinally extending axis thereof, a primary suspension spring comprising a beam of elastic polymeric material extending transversely of the sprung mass within said cross-member and having end portions project-ing outboard of generally vertical planes contain-ing the swing axes of said control arms, a pair of torsion rods extending on axes generally parallel but outboard said control arm swing axes and each connected at one end to a respective control arm and affixed at the other to an end of said beam, said rods being operative to carry to said beam forces deflecting said control arms relative the sprung mass, whereby the beam is adapted to bend under such forces about a spaced pair of nodal points located substantially inboard of said interconnec-tion locations, and reaction mount means on the sprung mass comprising an opposed pair of elastomer blocks seated on said cross-member and engaged with said beam at said nodal points thereof.