F O R M 2
THE PATENTS ACT, 1970 (39 of 1970)
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION
FRONT RIGID AXLE WITH FIVE-LINK SUSPENSION
2. APPLICANT(S)
(a) NAME FORCE MOTORS LIMITED
(b) NATIONALITY INDIAN Company
(c) ADDRESS MUMBAI-PUNE ROAD,
AKURDI, PUNE 411 035, MAHARASHTRA, INDIA

FIELD OF INVENTION
The present invention relates to a multi-link style suspension system utilized in utility vehicles equipped with a steerable front rigid axle. More particularly, the present invention relates to multi-link style suspension including an upper control arm, a lower control arm, and a lateral panhard rod enabling the axle to articulate in accordance to road inputs and terrain conditions.
BACKGROUND OF THE INVENTION
A vehicle's suspension system plays a vital role in both serving to isolate the occupants of the vehicle from the irregularities of the road surface, and aiding to improve the stability of the wheels by managing relative position of the wheels with respect to the vehicle body whilst ensuring consistent contact of the tyres with the terrain.
In the prior art U.S. Pat. No. US 3239235, discloses a vehicle suspension system wherein a pair of laterally spaced front road wheels are mounted on spindle members. Yoked spindle support members are pivotally connected to the spindle members so that they are free to pivot about a vertical axis for steering purpose. A solid axle is provided that has its end portions secured to each spindle support while its centre support is raised to extend in a transverse direction over the driveline of the vehicle. The centre of the solid axle is universally connected by a ball and socket joint to one end of a hinge plate. The other end of the hinge plate is connected to the vehicle body so that it pivots about an axis which extends transversely to the vehicle and is longitudinally spaced rearward from the spindle members. The principal objective of this invention is to provide a solid axle suspension system for an automotive vehicle that eliminates body roll, improves manoeuvrability and permits reduction in wheel rates.
In another prior art, an U.S. Pat. No. US 5820147 discloses steerable solid axle suspension for a vehicle, capable of eliminating the need for steering dampers includes a solid axle suspended from a vehicle frame by leaf spring assemblies and right and left shock absorbers. The suspension also includes a track bar laterally connecting the solid axle to the frame. The

suspension also includes a steering gear having a pitman arm connected to a drag link. The drag link extends downwardly to connect a tie rod which extends between and interconnects first and second steering knuckles.
In another prior art, U.S. Pat. Application No.US 2002/0067016 A1 discloses a four-link suspension system provides an almost infinite amount of adjustments to compensate for changing weather and road conditions. The suspension system includes a main support bracket with a plurality of holes formed therein for engaging a respective one of the plurality of holes formed in the main support bracket. The particular placement and combination of the holes in the main support bracket and each link, the size of each hold and slot, the shape of each link, the shape of the main support bracket, and the engagement of the links to the main support bracket permit the four-link suspension system to have hundreds of possible instant centre choices and locations. The assortment of configurations available allows the user to have an ideal-link suspension system for any particular application.
In yet another prior art, U.S. Pat. No. US 9096110 B1 discloses solid axle steering and suspension system. Accurate steering throughout suspension travel is satisfied with mechanical linkages that include a unique flexible joint-mounted bell crack. The suspension system comprises two pairs of links, each pair occupying opposite sides of a solid axle, this opposed configuration offering the axle centering capability of without the packaging constraints of a triangulated four-link suspension system, thereby facilitating its installation on production-based front solid axle vehicles.
OBJECT OF INVENTION
Steerable rigid axles are commonly used in heavy payload vehicles such as commercial trucks. They exhibit great load-bearing capacity while requiring fewer parts to manufacture. However, since most rigid axles are designed to be suspended via leaf springs, the setup inhibits the terrain handling capability of the vehicle. The predominant solution is to enhance the articulation and travel of the axle.
Therefore, the proposed design includes a suspension system with five-link suspension for a vehicle having a steerable front rigid axle. The frame of the vehicle is suspended above the

rigid axle, constrained with a pair of upper and lower control arms, each pair occupying opposing sides of the axle, that define the motion of the axle; a panhard rod assembled between the front rigid axle and the underbelly of the front section of the frame in a transverse direction; a pair of coil springs placed on either ends of the axle and is rigidly arrested to the frame via mounting brackets; dampers placed at either sides in the suspension system and are bolted at the mounting bracket; and an anti-roll bar positioned longitudinally ahead of the axle via a linkage pivoted in an axis that is parallel to the axis of the front axle; and wherein all the reaction loads on the front rigid axle is directly transmitted to the coil springs and wherein the weight of vehicle is solely supported by the wheels and the axle casing.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an isometric view of the suspension system in accordance with the present invention;
Figure 2 is a top view of suspension five-link suspension layout in accordance with the present invention;
Figure 3 is an assembly layout of suspension and steering components in accordance with the present invention;
Figure 4 is a front view of suspension assembly in accordance with the present invention;
Figure 5 is side view of suspension assembly in accordance with the present invention;
Figure 6 is an isometric view of the front axle and wheel/uprights in accordance with the present invention;
Figure 7 is a front view of the suspension arrangement in accordance with the present invention;
Figure 8 is a side view of the suspension arrangement in accordance with the present invention;
Figure 9 is top view of the steering system in conjunction with the suspension in accordance with the present invention;

DETAILED DESCRIPTION OF THE INVENTION
The multi-link style suspension system offers a compliant and a well-functioning method of suspending the axle of a vehicle and involves numerous links in different orientations in space as shown in Fig 1 and 2. This includes a pair of upper and lower control arms, and usually a lateral stabilizing device such a panhard rod. The combination of these linkages enables the axle to travel and articulate in accordance to road inputs and terrain conditions, whilst still providing a reasonably stable platform for the vehicle to be suspended on.
As shown in Fig 3 - 6, all the reaction loads on the front rigid axle [13] is directly transmitted to the two coil springs that are placed on the either ends of the axle and is rigidly arrested to the frame via mounting brackets [16]. Dampers are included at either sides in the suspension system and are bolted at the damper mounting bracket [7]. The axle encloses the drive shafts that transmit engine torque to the front wheels via CV joints that are enclosed within the axle casing. The differential sits directly within the axle casing, the weight of which is solely supported by the axle casing. The wheel uprights in this arrangement are bolted directly to the casing of the front rigid axle [13].
An anti-roll bar [10] is included in the assembly and is positioned longitudinally ahead of the axle. The anti-roll [10] bar is circular in its cross-section and is assembled with the aid of ball joints on the axle. This linkage is made to pivot in its lateral axis using two support bushes enclosed in mounting sleeves which are rigidly bolted to a transverse frame [1] member.
The arc of articulation the front axle is determined by the spacial orientation of a pair of upper [8] and lower control arms [9] that constraint the motion of the axle, in essence, forming a leading-arm to the axle. The lower control arm [9] in the system determines the location of the instantaneous centre of rotation of the axle along its lateral axis and the upper control arm [8] determines the lateral restraint point of the suspension system. Furthermore, the spacial arrangement of the upper [8] and the lower control arms [9] determines of the front suspension roll centre. In order to cater to lateral forces arising in the system, a panhard rod [11] is assembled between the front rigid axle [13] and the underbelly of the frontal section of the frame [1] in a transverse direction.

In this arrangement, the rotation input from the steering wheel is transferred the drop arm [4] via the re-circulating ball steering gearbox [3] that results into the translation of the tie rod [5]. The translatory motion of the tie rod [5] pivots the LH side wheel [2] about its steering axis and results in the lateral shift of the drag link [12] that rotates the RH side wheel [2]. A steering damper [14] is placed directly on the tie rod [5], the force on which is reacted by a mounting bracket on the frame [1].
The depicted arrangement of the present invention comprises of a system of linkages which governs vehicle steering as well as locates the axle throughout its full range of suspension travel. The system consists of four control arms, viz. two upper control arms and two lower control arms in a four-link arrangement as depicted in Figure 7 and Figure 8.
The links collectively act to position the axle throughout it's suspension travel. The link configuration represents a pair of upper links and a pair of lower arms; each pair occupying opposing sides of the axle, whereby the orientationof the upper arms keeps the axle centred beneath the vehicle throughout the suspension travel, thereby restricting the lateral movement of the axle whilst permitting vertical articulation.
The upper control arms are crucial in determination of roll axis of the vehicle and its anti – dive geometry. All loads that occur between the sprung and unsprung masses are reacted through the coils springs and the control arms. The longitudinal loads of braking and acceleration are coupled through the side view instant centre and the lateral loads are couple through the roll axis.
The suspension system also includes an anti-roll bar that is connected to either ends of the axle and is pivoted beneath the frame member, thus enabling the system to articulate the wheels without inducing excessive roll in the sprung mass. A panhard rod mounted transverse to the vehicle frame works in coherence with the upper control arms to cater to lateral loads that the axle is subjected to whilst negotiating corners. The link is designed and positioned to offer minimal hindrance to the articulation of the rigid axle and to reduce the effect of bump steer that is associated with installation of lateral stabilizing bars on rigid axles.

The system also consists of a drag link having first end connected to the first steering knuckle and extending to a second end connected to the second steering knuckle. The LH side wheel assembly is pivoted around its steering axis with the aid of a tie rod which is translated in conjunction with a re-circulating-ball steering gearbox mounted on the frame as depicted in Figure 9.
Advantageously, the positioning of these connections permits the decoupling of the steering mode from tilt motion generated by typical driving and road inputs to the suspension system.

List of Reference Numerals Utilized in the Drawings
1. Frontal section of vehicle frame
2. Tyre
3. Recirculating ball steering gearbox
4. Drop arm
5. Tie rod
6. Coil spring mounting bracket
7. Damper mounting bracket
8. Upper control arm of suspension linkage
9. Lower control arm of mounting bracket

10. Anti-roll bar
11. Panhard rod / Stabilizing bar
12. Drag link
13. Front rigid axle
14. Steering damper
Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. It will be apparent to those having ordinary skill in the art that a number of changes, modifications, variations, or alterations to the invention as described herein may be made in complete specification, none of which depart from the spirit or scope of the present when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

WE CLAIM:
1. A suspension design with five-link suspension for a vehicle having a steerable front
rigid axle;
the frame of the vehicle is suspended above the rigid axle, constrained with a pair of
upper and lower control arms, each pair occupying opposing sides of the axle, that
defines the motion of the axle;
a panhard rod assembled between the front rigid axle and the underbelly of the front
section of the frame in a transverse direction;
a pair of coil springs placed on either ends of the axle and is rigidly arrested to the
frame via mounting brackets;
dampers placed at either sides in the suspension system and are bolted at the damper
mounting bracket;
and an anti-roll bar positioned longitudinally ahead of the axle via a linkage pivoted in
an axis that is parallel to the axis of the front axle;
and wherein all the reaction loads on the front rigid axle is directly transmitted to the
coil springs and wherein the weight of vehicle is solely supported by the wheels and
the axle casing.
2. The front rigid axle with five-link suspension, according to claim 1, wherein, the said wheel uprights in this arrangement are attached directly to the casing of the axle.
3. The front rigid axle with five-link suspension, according to claim 1, wherein, the said axle casing encloses the drive shafts that transmit engine torque to the front wheels via CV joints.
4. The front rigid axle with five-link suspension, according to claim 1, wherein, the said linkage is made to pivot about a lateral axis with two support bushes enclosed in mounting sleeves which are rigidly bolted to a transverse frame member.
5. The front rigid axle with five-link suspension, according to claim 1, wherein, the spacial orientation of the said pair of upper and lower control arms determines the arc of articulation the front axle and the front suspension roll centre.

6. The front rigid axle with five-link suspension, according to claim 1, wherein, the said lower control arm determines the location of the instantaneous centre of rotation of the axle along its lateral axis.
7. The front rigid axle with five-link suspension, according to claim 1, wherein, the said upper control arm determines the lateral restraint point of the suspension system.
8. The front rigid axle with five-link suspension, according to claim 1, wherein, the rotation input from the steering wheel is transmitted to the drop arm via the recirculating ball steering gearbox resulting in the translation of the tie rod.
9. The front rigid axle with five-link suspension, according to claim 8, wherein, the translatory motion of the tie rod pivots the left hand side wheel about its steering axis and results in the lateral shift of the drag link that rotates the right hand side wheel.
10. The front rigid axle with five-link suspension, according to claim 1, wherein, the steering damper is placed directly on the tie rod, the force on which is reacted by the said mounting bracket on the frame.
11. The front rigid axle with five-link suspension, according to claim 1, further includes a drag link having first end connected to the first steering knuckle and extending to a second end connected to the second steering knuckle.