CA2176318A1 - Vehicle suspension system - Google Patents

Abstract

The suspension for an axle of a vehicle such as a motor coach includes a rigid transverse axle which is suspended relative to a frame of the vehicle by springs and control links. The control links include a V-shaped link with an apex of the V connected to the axle and legs of the V extending rearwardly for connection to the frame at ends of the legs. Forwardly of the axle is provided a pair of arms each connected at a rear end to the axle at a forward end to the frame. The V link is inclined from the apex at the top of the axle downwardly and rearwardly. The arms are inclined from a bottom of the axle upwardly and forwardly. When the axle includes steered wheels, the steering system includes a steer rod parallel to the axle, a drag rod substantially at right angles to the axle and an idler drive member mounted on the axle for pivotal movement about substantially vertical axis such that forward and rearward movement of the drag rod effects side to side movement of the steer rod.

Description

~ ~ 2i7~3~
VEHICLE SUSPENSiON SYSTEM
BACKGROUl~n OF THE INVF~TION
This invention telates to a vehicle suspension system includin~
a vehicle body having frame members, an axle having ground wheels 5 mounted at respective ends of the axle, suspension springs i"le(~onne~ ~i"g the sxle and the frame members allowins suspension movement of the axle relative to the body and a control link system connected between the vehicle body and the axle for co"l,~ ~g the suspension movement.
The vehicle suspension of the present ~nvention is particularly 10 but not exclusively designed for the steering axle of a vehicle such as a motor coach.
It is well known in vehicle suspension systems that the control links conlle~ Lt:d between the vehicle body and the axle can include two ~enerally parallel radius rods which have one end con,~ Led to the axle and 15 the opposed end connected to the vehicle body. It is also known that a V-link system includin~ an apex connected to the axle and a pair of legs the end of which is attached to the vehicle body can be used. Various configurations of these links have been proposed including an all trailing arran~ement in which the trailing ends of the links are attached to the axle 20 and the links both extend forwardly from the axle for e,LIach"~enL to the body. Other proposed linkage arran~ements have included an all leading arran8ement in which the leadin~ end of the links is attached to the axle and the links trail from the axle to the vehicle body.
In this field, the term "trailing" is used to define a link which 25 has a forward end sttached to the vehicle body and trails therefrom to the axle and conversely the term "leading~ is used to define a link which has a rearward end attached to the vehicle body and leads therefrom ~o the axle.

1~ ~17~318 SUMMARY OF THE INVENTION
it is one object of the present invention, however, to provide an improved configuration of the control links which provides advantages in the handling cllaracleri~lics of the vehicle.
According to one aspect of the invention there is provided a vehicle suspension comprising: a vehicle body; a horizonta~ axle ~L~ 8 transversely across the vehicle body; two ground wheels each mounted on a respective end of the axle on a respective side of the vehicle body for rotation about a horizontal rotation axis longitudinal of the axle and transverse to the vehicle body; the vehicle body having frame members thereon for transmitting forces from the body to the axle; spring means interconnecting the axle and the frame members allowing suspension movement of the axle relative to the body; and control links connected between the vehicle body and the axle for cor,LI( " ,9 suspension movement;
th~ control links including: a first link system defined by a V-link system which is sulJ5Ldl~ y V-shaped in plan view having an apex connected to tha axle adjacent a mid point thereon by at least one mounting bushing and a pair of legs each extending away from the axle and outwardly toward a rcspective side of the vehicle body and each conne.,Led to the vehicle body by a respective mounting bushing; and a second link system defined by two link arms each haYing an end connected to the axle by a mounting bushing at a position on the axle spaced outwardly to a respective side of the apex and each extendin~ away from the axle to an end thereof connected to the vehicle body by a respective mounting bushing; one of the first and second link systems being leading and the other being trailing; and the connection to the axle of the trailing link system being at a hei~ht on the axle which is lower than the connection to the axle of the leading link system.

2~7&3~8 The configuration of the necessary control links for a vehicle suspension requires an extremely co" ,, " - ~ed " ,eclla~ ' engineering analysis~ The analysis involves the ~ ala~ s of the suspension in various modes including bump-steer, roll-steer and compliance-steer. In addition it is desirable to provide a control link system which has anti-dive a,a~leli~lics in br2king. These cl~là,,lerblics of a suspension system involve complex calculations and imperical analysis since the cl~a,~ ri:ilics ar~ interdependent. The selection therefore of a particular linkage arrangement must be supported by a series of calculations and analysis to confirm that the linkage will operate to provide the required characteristics.
While the individual elements of the system including the link arms and the V-link are themselves known, the compleity of suspension systems in general mean that it is not possible to simply move one element from one position to another without completely changin~q the characteristics of the system.
The description herein will not set out in detail the calculations and the particular cha,al,~e~ ics which are obtained but will instead describe the structure which results from this complex analysis.
The arrangement has the following preferable features:
Preferably the pair of legs of the V-link system are rigidly co,llle~,~ed to~ether to form a rigid V-link and are col-ne.,led to the axle by a single bushing at the apex. Alternatively, the V-link can be formed by two separate arms which are individually mounted on the axle by a separate bushing but the bushings are sufficiently close together to define in effect a single pivot location.
Preferably the first link system is leading and the second link system is trailing.

~7~3~8 Preferably the connection to the axle of the trailing link system is arranged at a height on the axle which is lower than the horizontal rotation axis of the axle and the connection to the axle of the leading link system is arranged at a height above the horizontal rotation axis of the axle.
P~rt:lably the connection to the axle of the leading link system is arranged forwardly of a vertical plane of the axle containin3 the rotation axis.
Preferably the connection to the axle of the trailir~g link system is arranged rearwardly of a vertical plane of the axle containing the rotation 1 0 axis.
Preferably, in an equilibrium position of the vehicle body and the axle, the V-link system is inclined from the apex downwardly so that the ends of the legs are at a height lower than that of the apex.
Each of the ground wheels is preferably mounted on the axle for steering movement about a vertical steering axis adjacent the respective end of tho axle, each of the ground wheels being connected with a tie rod extending parallel to the axle and including steering means for effecting said steering movement of the ground wheels, the steering means including a steer rod parallel to the axle, a drag rod substantially at right angles to the axle and extending substantially hori~o~ 'y forwardly therefrom and an idler drive member mounted on the axle for pivotal movement about a sub ~la~ a:~y vertical axis such that forward and rearward movement of the dra3 rod effects side to side movement of the steer rod and a pitman arm at a forward end of the drag rod for effecting said forward and rearward movement of the drag rod. The pitman arm is mounted for pivotal movement about a vertical axis. The idler drive member is mounted adjacent a mid point of the axle with the dra~q rod extending forwardly therefrom at a position between the frame members of the vehicle body.
.

' ~ 217~31~

One important aspect of the suspension system is to limit or prevent axle yaw that is pivotal movement about a vertical axis tendin~ to effect a steerin~ action of the wheels on the axle, in rsspons~ to vehicle roll while usin~ a link arm system in which the link arms are inclined upwardly 5 from the axle in the equilibrium or rest position of the axlc on the vehicle.
Accordin~ to a second aspect of the invention there is provided a vehicle suspension co",l,ri~;"~: a vehicle body; a horizontal axle extending transversely across the vehicle body; two ~round wheels each mounted on a respective end of the axle on a respective side of the vehicle body for 10 rotation about a horizontal rotation axis longitudinal of the axle and transverse to the vehicle body; the vehicle body havin~ frame members thereon for llarl:,llli~Lill~ forces from the body to the axle; sprin~ means interconnectin~ the axle and the frame members allowing suspension movement of the axle relative to the body; and control links connected 15 between the vehicle body and the axle for controllin~ suspension movement;
the control links including two link arms each havin~ an end connected to the axle by a mountin~ bushing at a position on the axle spaced outwardly to ~ respective side of a mid point of the axle and each extendin~ away from the axle to an end thereof connected to the vehicle body by a 20 respective mountin~j bushin~; wherein in an equilibrium position of the vohicle body and the axle: the link arms are inclined at a rake angle upwardly from the ends thereof connected to the axle so that the ends thereof co,-,le~;led to the vehicle body are arran~ed at a hei~ht aboYe the ends conne~ilffd to the axle; and the link arms are arran~qed at a taper angle 25 to a vertical plane containin~ the ends conne. ~d to the axle such that a horizontal spacin~ between the ends connected to the axle is different from the horizontal spacin~ between the ends conne~ l~d to the vehicle body; the ~ '~17~318 taper angle and the rake angle being arranged such that axle yaw in response to roll of the vehicle body is reduced.
One e"~bod~."e"L of the invention will now be described in conJunction with the accor"panying drawings in which:
5 B~IFF DESCRIPTION OF THE DRAWINGS
Figure 1 is a computer generated side view of the suspension of 8 vehicle.
Figure 2 is a top plan view of the suspension of Figure 1.
Figure 3 is an isometric view of the suspension of Figures 1 and 10 2.
Figure 4 is a top plan view of the same suspension showing the steering arran~ement with part of the suspension and the vehicle frame and the vehicle frame structure omitted for convenicnce of il~ustration.
In the drawings like characters of reference indicate 15 co-~spond;~lg parts in the different figures.
DETAI~ED DESCRIPTION
The vehicle and suspension of the present invention includes a vehicle 10 which is shown only schematically since the main structure of the frame of the vehicle will be well known to one skilled in the art and can 20 be modified in accordance with requirements. The vehicle with which the present suspension system is intended to be used is a highway coach but the suspension system can of course be used for other vehicles.
The only elements of the vehicle frame which are shown comprise an arched support structure 11 and 12 located part way across 25 the vehicle together with a rear support plate 13 and a front support p~ate 14 which are conne. l~d to the longitudinal main frame of the vehicle.
The arched support elements 11 and 12 each include a vertical tear leg 15, a horizontal main beam and a vertlcal front leg 17. On the ' ~ 217~18 beam 16 is mounted a l~cepla.,ld 19 for an upper end of a support spring which transmits a vertical load from the arch support to a horizontal axle 20 of the vehicle. The spring elements are not shown for convenience of illustration and again these will be well known to one skilled in the art and 5 generally comprise coi"",e,~,iâlly available gas sprin~s. The axle 20 includesa pair of support pads 21 and 22 each in the form of a rectangular plate on an upper su~face of the ax~e for engaging the bottom of the gas spring.
The axle 20 as best shown in Fi~ure 3 comprises a cast elongatc axle member with two outer sections 23 and 24 outwardly of the pads 21 and 22 and a central dropped section 25 between the pads 21 and 22. Thus the dropped section is inclined downwardly and inwardly just inside the pads 21 and 22 and then has a horizontal beam defined in the dropped sQction 25 which is dropped by a distance of the order of six inches relative to the two outer sections 23 and 24. At the outer end of 15 each outer section is provided a king pin steering mount 26 of a conventional nature for receiving a steetable ground wheel 27.
The cast axle member includes orl the underside of each of the outer members 23 and 24 aligned with the p8~ 21, 22 a vertical dependin~
portion 28 carryin~ a mounting structure for a bushing genera~ly indicated at 20 29.
At a center of the drop section 25 is provided a mounting tower 31 having a bushing 32 mounted thereon.
The suspension system for controlling the movement of the axle relative to the vehicle frame comprises a leading V-link 33 and a pair of 25 trailin~ link arms 34 and 35.
The leading V-link shown in plan in Figure 2 includes a front apex 36 and a pair of trailing legs 37 and 38 which extend from the apex ~sarvJa~dly and outwardly. The trailing link arms 34 and 35 each comprise a ~ ~1763~ 8 separate link arm which is SUIJ~"~ Y straight and extends forwardly and slightly inwardly from the axle. Each of the suspension members provided by the trailing link arms and the V-link is mounted on the axle at one end and on the Yehicle frame at the opposed end. Each mounting point 5 comprises a conventional bushing of the type comprisins a central shaft 40 which is mounted either on the axle or on the vehicle, a rubber or flexible bushing surroundin~ the shaft and a collar 41 carried on the respective suspension member. Such bushings are of course well known and therefore do not need to be illustrated in detail. Each bushing basically allows rotation 10 of the suspension element about the axis of the shaft while allowing some flexin~ or twisting of the collar relative to the shaft due to col"pres,ion of the bushing.
The apex of the V-link is located on a bridge 31 at a top of the axle and above an axis 43 of rotation of the ground wheels 27 The bridge 31 connects across the towers 21 and 22 and thus forms part of the elements attached to the towers as part of the sprin~ mountin~ elements rat~er than a part of the axle itself leavin~ a space underneath the bridge for the idler 53 described her~i"drler. The axis of the shaft of the bushin~ of the apex is also forward of the axis 43 so that the legs extend from that 20 position forward of the axis rearwardly of the axis to the rear bushings 44 and 45 at the rear end of the trailing legs 37 and 38. The rear bushin~s 44 and 45 are mounted on support brackets inside the main arch supports 11 and 12 with those bushings located slightly downwardly of the bushing at the apex so that the trailing legs extend rearwardly, outwardly and also 25 sllghtly downwardly.
As best shown in Figure 1, the trailing link arms 34 and 35 have a rear bushing 29 at the bottom of the axle below and rearwardly of th~ axis 43. The link arms 34 and 35 have a forward bushing 46 and 47 ~ 2176318 which Is mounted on the bottom of the front leg 17 of the arch supports 11 and 12. The bushings 46 and 47 are slightly above the bushings 29 so that each trailing link arm trails from the bushing 46, 47 rearwardly together with slightly outwardly and slightly downwardly. These angles define a rake 5 angle R as shown in Figure 1 relative to a hor~zontal plane H and a taper an~le T relative to a vertical plane V.
The specific angles R and T of the trailing legs and the trailing link arms relative to the horizontal can be selected in accorda,)ce with calculated or empirical determination of the various characteristics of 10 movement of the axle relative to the frame to provide the required inherent steering effects discussed hereinbefore. In particular, the selection of the angles can be arranged so that the tendency of the axle to steer, that is to pivot about a vertical axis, in response to rolling movement of the vehicle body is reduced or prevented by the use of the positive angles T and V.
The steering system shown in Figure 4 includes a pitman arm 50 mounted on a vertical drive shaft 51 of the steering system for mcvement of the pitman arm 50 in a horizontal plane. The pitman arm is attached to a drag link 52 which extends horizontally rearwardly from an outer end of the pitman arm in the trailing direction from a position forwardly of the axle 20 to a position at the axle for effecting a steering action.
An idler drive member 53 is mounted for pivotal movement about a vertical pivot shaft 54 carried on the drop portion 25 of the axle so that forward and rearward movement of tha dra~ rod 52 causes side to side ~liding movement of a shaft 55 of thQ idler drive member 53. The shaft 55 carrles a steering link rod 56 which extends from the shaft 55 outwardly to a steering link 57 of one of the ground wheels 27. That steering link 57 is ~ 217~318 ~o connected to the steering link 58 of the other ground wheel by 8 tie rod 59 extendin~ parallel to the axle 20.
In an alternative a"ange",~"~ (not shown) the tie rod 59 can be omitted and instead a second steering rod similar to the rod 56 is connected 5 from the idler 53 to the steering link 58.
In the arrangement as shown, the V-link is leading while the arms are trailing. This can be reversed provided one is trailing and the other is leading and provided the trailing system is connected to the axle at a point thereon which is lower than the leading system.
Since various ,,,odificc,lions can be made in m~ invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without departing from such spirit and scope, it is intended that all matter contained in the accompanying speciriGalion shall be i,1lerp"d~ as illustrative only and not in 15 a limiting sense.

Claims (14)

CLAIMS:

1. A vehicle suspension comprising:
a vehicle body;
a horizontal axle extending transversely across the vehicle body;
two ground wheels each mounted on a respective end of the axle on a respective side of the vehicle body for rotation about a horizontal rotation axis longitudinal of the axle and transverse to the vehicle body;
the vehicle body having frame members thereon for transmitting forces from the body to the axle;
spring means interconnecting the axle and the frame members allowing suspension movement of the axle relative to the body;
and control links connected between the vehicle body and the axle for controlling suspension movement;
the control links including:
a first link system defined by a V-link system which is substantially V-shaped in plan view having an apex connected to the axle adjacent a mid point thereon by at least one mounting bushing and a pair of legs each extending away from the axle and outwardly toward a respective side of the vehicle body and each connected to the vehicle body by a respective mounting bushing;
and a second link system defined by two link arms each having an end connected to the axle by a mounting bushing at a position on the axle spaced outwardly to a respective side of the apex and each extending away from the axle to an end thereof connected to the vehicle body by a respective mounting bushing;
one of the first and second link systems being leading and the other being trailing;

and the connection to the axle of the trailing link system being at a height on the axle which is lower than the connection to the axle of the leading link system.

2. The vehicle suspension according to Claim 1 wherein the pair of legs of the V-link system are rigidly connected together to form a rigid V-link and are connected to the axle by a single bushing at the apex.

3. The vehicle suspension according to Claim 1 wherein the first link system is leading and the second link system is trailing.

4. The vehicle suspension according to Claim 1 wherein the connection to the axle of the trailing link system is arranged at a height on the axle which is lower than the horizontal rotation axis of the axle and the connection to the axle of the leading link system is arranged at a height above the horizontal rotation axis of the axle.

5. The vehicle suspension according to Claim 1 wherein the connection to the axle of the leading link system is arranged forwardly of a vertical plane of the axle containing the rotation axis.

6. The vehicle suspension according to Claim 1 wherein the connection to the axle of the trailing link system is arranged rearwardly of a vertical plane of the axle containing the rotation axis.

7. The vehicle suspension according to Claim 1 wherein, in an equilibrium position of the vehicle body and the axle, the V-link system is inclined from the apex downwardly so that the ends of the legs are at a height lower than that of the apex.

8. The vehicle suspension according to Claim 1 wherein, in an equilibrium position of the vehicle body and the axle:
the link arms are inclined at a rake angle upwardly from the ends thereof connected to the axle so that the ends thereof connected to the vehicle body are arranged at a height above the ends connected to the axle;
and the link arms are arranged at a taper angle to a vertical plane containing the ends connected to the axle such that a horizontal spacing between the ends connected to the axle is different from the horizontal spacing between the ends connected to the vehicle body;
the taper angle and the rake angle being arranged such that axle yaw in response to roll of the vehicle body is reduced.

9. The vehicle suspension according to Claim 3 wherein the axle includes a dropped center part thereof at a height lower than ends thereof, wherein the axle includes two towers each for connection to a respective spring and wherein the apex is connected to a bridge portion bridging the towers and arranged at a height above the dropped center part.

10. The vehicle suspension according to Claim 1 wherein each of the ground wheels is mounted on the axle for steering movement about a vertical steering axis adjacent the respective end of the axle, each of the ground wheels including steering means for effecting said steering movement of the ground wheels, the steering means including a steer rod parallel to the axle, a drag rod substantially at right angles to the axle and extending substantially horizontally forwardly therefrom and an idler drive member mounted on the axle for pivotal movement about a substantially vertical axis such that forward and rearward movement of the drag rod effects side to side movement of the steer rod and a pitman arm at a forward end of the drag rod for effecting said forward and rearward movement of the drag rod.

11. The vehicle suspension according to Claim 10 wherein the axle includes a dropped centre part thereof at a height lower than ends thereof, the idler drive member being mounted on the drop portion of the axle.

12. The vehicle suspension according to Claim 10 wherein the pitman arm is mounted for pivotal movement about a vertical axis.

13. The vehicle suspension according to Claim 10 wherein the idler drive member is mounted adjacent a mid point of the axle with the drag rod extending forwardly therefrom at a position between the frame members of the vehicle body.

14. A vehicle suspension comprising:
a vehicle body;
a horizontal axle extending transversely across the vehicle body;
two ground wheels each mounted on a respective end of the axle on a respective side of the vehicle body for rotation about a horizontal rotation axis longitudinal of the axle and transverse to the vehicle body;
the vehicle body having frame members thereon for transmitting forces from the body to the axle;
spring means interconnecting the axle and the frame members allowing suspension movement of the axle relative to the body;
and control links connected between the vehicle body and the axle for controlling suspension movement;
the control links including two link arms each having an end connected to the axle by a mounting bushing at a position on the axle spaced outwardly to a respective side of a mid point of the axle and each extending away from the axle to an end thereof connected to the vehicle body by a respective mounting bushing;
wherein, in an equilibrium position of the vehicle body and the axle:

the link arms are inclined at a rake angle upwardly from the ends thereof connected to the axle so that the ends thereof connected to the vehicle body are arranged at a height above the ends connected to the axle;
and the link arms are arranged at a taper angle to a vertical plane containing the ends connected to the axle such that a horizontal spacing between the ends connected to the axle is different from the horizontal spacing between the ends connected to the vehicle body;
the taper angle and the rake angle being arranged such that axle yaw in response to roll of the vehicle body is reduced.