Note: Descriptions are shown in the official language in which they were submitted.
~ ~ 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.
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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.
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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
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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
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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
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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
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~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.
