FORM 2
The Patent Act 1970
(39 of 1970)
AND
The Patent Rules, 2005
COMPLETE SPECIFICATION (SEE SECTION 10; RULE 13)
TITLE OF THE INVENTION
STEERING LINKAGE FOR INDEPENDENT SUSPENSION WITH STEERING TRAY AND T-LINK
APPLICANT
APPLICANTS
TATA MOTORS LIMITED
an Indian company having its registered office at Bombay house,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001,
Maharashtra, India.
AND
HENDRICKSON TRUCK COMMERCIAL VEHICLE SYSTEMS
a US Company having address
Hendrickson USA, L.L.C.,
500 Park Boulevard,
Suite 1010, Itasca,
Illinois 60143-1285,
U.S.A.
The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
[0001] The present invention relates to vehicle steering apparatus. More particularly to a vehicle steering apparatus for steering front axles of a vehicle with independent suspension having ladder type chassis design.
BACKGROUND OF THE INVENTION
[0001] Conventional personal automotive vehicles are known to suffer significant deficiencies in steering and general handling capability due to the steering and suspension systems typically employed therein. More particularly, heavy-duty vehicles with independent suspension have to cater to high load requirements and high articulation requirements due to off-road conditions. In addition to high loads, the high articulations also lead to high Bump steer values on such vehicles. This is particularly hazardous to steering kinematics of such vehicles. As is well known, during the turning of such vehicle, centrifugal force acts upon the vehicle radially outwardly of the turn creating a tendency of the vehicle to roll about an axis extending longitudinally of the vehicle.
[0002] FIG. 1 illustrates a perspective view of a conventional steering linkage for twin-steer independent suspension vehicle, according to the prior art. The vehicles comprises dual pivots, one each on Left-hand (LH) and Righ-hand (RH) long member of chassis. It can be clearly referred from the FIG. 1 that if there is a requirement to increase frame width to accommodate bigger engines/transmission, the steering linkage of the vehicle will lead to reduction in length of tie-rods, thus increasing the bump steer. This deteriorates the steering kinematics of vehicle and leads to more tyre wear during wheel articulations. In addition, as the pivots are mounted on long members, these will be in vicinity of tyres during turn, thus reducing the lock angles and increasing Turning Circle Diameter (TCD).

[0003] Therefore, the Bump steer Kinematics can be improved by increasing the length of tie-rods for individual wheels and carefully selecting the tie-rod hard points. Same can be achieved for lighter vehicles with smaller engines as the chassis width can be conveniently reduced to push the tie-rod mounting on chassis inboard. But, these days, heavier vehicles capable of off-road mobility have to be provided with heavier engines. Thus, a wider chassis is required to accommodate the same, particularly in the region of first axle. Thus, it is desired to address the above mentioned disadvantages or other shortcomings or at least provide a useful alternative.
OBJECT OF THE INVENTION
[0004] The principal object of the present invention is to provide a vehicle steering apparatus for steering front axles of a vehicle with independent suspension having higher chassis width in front with better steering kinematics and lower a Turning Circle Diameter (TCD).
[0005] Yet another object of the present invention is to provide better steering kinematics especially lower Bump steer, lower tyre wear, simplified wheel lock bolt arrangement and lower the TCD for the vehicle.
SUMMARY OF THE INVENTION
[0006] In accomplishing the objects of the invention, there has been provided, according to one aspect of the invention, a vehicle steering apparatus for steering front axles of a vehicle with independent suspension. The vehicle steering apparatus includes a steering gearbox, a left-hand (LH) tie-rod and a right-hand (RH) tie-rod, a pair of idler arms connected to the LH tie-rod and the RH tie-rod, a common T-link connected to the pair of idler arms to drive the LH Tie-rod and the RH Tie-rod, a pitman arm connected to the steering gearbox to provide motion to the common T-link, and a steering Tray to provide an inboard mounting for the

idler arms. The idler arms rotate the steering tray providing motion to the LH and RH tie-rods of RH and LH wheels of the vehicle.
[0007] In an embodiment, the inboard mounting for the idler arms maximizes steering angles and minimizes bump steer.
[0008] In an embodiment, the steering tray is mounted on both sides of a chassis of the vehicle using a rigid mounting bracket and facilitates the inboard mounting for the idler arms.
[0009] In an embodiment, wherein the idler arms are mounted on the steering tray connected to the LH tie-rod and the RH tie-rod using the rigid mounting brackets.
[0010] In an embodiment, the steering tray is equipped with integrated a RH steering lock and a LH steering lock for full LH and RH turns.
[0011] In an embodiment, the RH tie-rod arms is connected to RH wheel end to provide steering to the RH wheel and the LH tie-rod arms is connected to LH wheel to provide steering to RH wheel of the vehicle.
[0012] In an embodiment, the common T-link connects to the Idler arms to the input through drag link from Pitman arm and tie-rods that connect Idler arms to wheels of the vehicle.
[0013] In an embodiment, the idler arms are mounted away from the wheels to increase wheel lock angles without interfering with the idler arms.
[0014] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however,

that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF FIGURES
[0015] This method and system is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0016] FIG. 1 illustrates a perspective view of a conventional steering linkage for twin-steer independent suspension vehicle, according to the prior art;
[0017] FIG. 2 illustrates a perspective view of a vehicle steering apparatus for steering front axles of a vehicle with independent suspension, according to an embodiment as disclosed herein;
[0018] FIG. 3 illustrates an isometric view of the vehicle steering apparatus with all integrated components, according to an embodiment as disclosed herein;
[0019] FIG. 4 illustrates a top view of a first axle steering linkage with high frame width, according to an embodiment as disclosed herein;
[0020] FIG. 5 illustrates steering linkage in RH steered condition along with wheel positions, ,according to an embodiment as disclosed herein;

[0021] FIG. 6 illustrates steering linkage in LH steered condition along with wheel positions, according to an embodiment as disclosed herein; and
[0022] FIG. 7 illustrates a Bump Steer Graph for vehicle steering apparatus, according to an embodiment as disclosed herein.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments. The term “or” as used herein, refers to a non-exclusive or, unless otherwise indicated. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein can be practiced and to further enable those skilled in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0024] Embodiments herein discloses a vehicle steering apparatus for steering front axles of a vehicle with independent suspension. The vehicle steering apparatus includes a steering gearbox, a left-hand (LH) tie-rod and a right-hand (RH) tie-rod, a pair of idler arms connected to the LH tie-rod and the RH tie-rod, a common T-link connected to the pair of idler arms to drive the LH Tie-rod and the RH Tie-rod, a pitman arm connected to the steering gearbox to provide motion to the common T-link, and a steering Tray to provide an inboard mounting for the idler arms. The idler arms rotate the steering tray providing motion to the LH and RH tie-rods of RH and LH wheels of the vehicle.

[0025] Unlike the conventional systems, the proposed vehicle steering apparatus is reliable and provides effective solution for steering of vehicles with independent suspension having higher chassis width in the front. The proposed vehicle steering apparatus provides better steering kinematics especially lower Bump steer, lower tyre wear, simplified wheel lock bolt arrangement and lower Turning Circle Diameter (TCD).
[0026] Unlike the conventional systems, the vehicle steering apparatus not only provides a rigid structure for mounting of the idler arms on the chassis but also shifts the tie-rod connections for wheel-ends towards vehicle center thus leading to higher length of tie-rods and lower bump steer. The steering tray is mounted on both sides of the chassis long members with the help of rigid mounting brackets and facilitates inboard (close to vehicle center) mounting for the idler arms. The steering tray is also equipped with integrated lock bolt arrangement for full LH and RH turns. The idler arms rotate on the steering tray providing motion to independent tie-rods of the two wheel ends. This inboard mounting of idler arms provides enough space for having long tie-rods. Combining this with proper kinematic study and arrangement of hard-points leads to lower bump steer and better Steering kinematics. In addition, with inboard mounting of the idler arms, there is less interference with wheels in steered conditions and thus higher lock angles can be maintained to achieve the lower TCD.
[0027] The accompanying drawings are used to help easily understand various technical features and it should be understood that the embodiments presented herein are not limited by the accompanying drawings. As such, the present disclosure should be construed to extend to any alterations, equivalents and substitutes in addition to those which are particularly set out in the accompanying drawings. Although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are generally only used to distinguish one element from another.

[0028] Referring now to the drawings, and more particularly to FIGS. 2 through 7, there are shown preferred embodiments.
[0029] FIG. 2 illustrates a perspective view of a vehicle steering apparatus, according to an embodiment as disclosed herein for steering front axles of a vehicle with independent suspension. It can be clearly referred from the FIG. 2 that chassis width is low at a second axle and high at a first axle. This is due the fact that off-road mobility vehicles require highly powered engines that are typically packaged at front of the vehicle under cabin. The proposed arrangement in the vehicle steering apparatus helps in better steering kinematics, lower the TCD and integrated lock bolt arrangement on steering tray.
[0030] FIG. 3 illustrates an isometric view of the vehicle steering apparatus with all integrated components, according to an embodiment as disclosed herein. The vehicle steering apparatus comprises a steering gearbox (1) connected to a pitman arm (2) that provides motion to a common T-link (4). The T-link (4) is connected to a pair of idler arms (8, 9) that drive a LH Tie-rod (10) and a RH Tie-rod (11). In an embodiment, the common T-link (4) connects to the idler arms (8, 9) to through a drag link (3) from the pitman arm (2) and the LH Tie-rod (10) and the RH Tie-rod (11) that connect the idler arms (8, 9) to LH and RH wheels of the vehicle.
[0031] The Idler Arms (8, 9) are mounted on a steering tray (5) connected to LH and RH long member with mounting LH bracket (6) and RH bracket (7). This steering tray (5) is designed to provide an inboard mounting for the idler arms (8, 9) to maximize steering angles and minimize bump steer. The steering tray (5) is also equipped with integrated RH steering lock (12) and LH steering lock (13) in a particular arrangement to simplify wheel ends. The tie-rod arms (10, 11) are connected to LH and RH wheel ends (not shown) to provide steering to the RH and LH wheels of the vehicle. The idler arms (8, 9) rotate the steering tray (5)

providing motion to the LH and RH tie-rods (10. 11) of the RH and LH wheels of the vehicle.
[0032] FIG. 4 illustrates a top view of a first axle steering linkage with high frame width, according to an embodiment as disclosed herein. Due to high width of the chassis, the linkage, if mounted as per the typical arrangement of the idler arms (8, 9) mounting directly on the LH and RH long member, will lead to small length of the tie-rod arms (10, 11) and high bump steer. This effects the steering kinematics of the vehicles that becomes hazardous to drive in the off-road conditions that encounter frequent suspension articulations. The proposed invention illustrates the new steering tray design for inboard mounting of the idler arms (8, 9). This will not only improves the packaging feasibility of the linkage but also enhances the steering performance due to higher length of the tie-rod arms (10, 11) and leads to better steering kinematics.
[0033] FIG. 5 illustrates steering linkage in RH steered condition along with wheel positions, according to an embodiment as disclosed herein.
[0034] Another advantage of this linkage is that this enables to achieve higher lock angles of the wheels that in turn enables to get the lower TCD for the vehicle. This is another very critical performance criterion to drive the vehicle in the off-road conditions. As the idler arms (8, 9) are mounted away from the steered wheels, it provides more freedom to increase the wheel lock angles without interfering with the Idler arms (8, 9). For maintaining Ackerman of the steering, higher lock angles are required on the first axle than the second axle that makes the first axle linkage design more critical. The proposed invention also boasts of this advantage of lower TCD in addition to improved steering kinematics and improved packaging. The steering tray (5) is also equipped with the integrated lock bolt arrangement that simplifies the wheel-ends to a great extent. As the wheel-ends also undergo bump and rebound articulations in

addition to steering articulations, lock bolt integration on wheel ends becomes a tedious task.
[0035] FIG. 6 illustrates steering linkage in LH steered condition along with wheel positions with RH lock-bolt engagement, according to an embodiment as disclosed herein; and
[0036] FIG. 7 illustrates a bump steer graph for vehicle steering apparatus, according to an embodiment as disclosed herein. A toe change graph of the steering linkage with respect to wheel articulations showing the improved steering kinematics of the first axle is illustrated in the FIG. 7. As bump is the more frequent phenomenon in the off-road mobility, a lower bump steer is preferred in these vehicles. The linkage achieves a bump steer of less than 0.1° in all wheel articulations.
[0037] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

We Claim:
1. A vehicle steering apparatus for steering front axles of a vehicle with
independent suspension, comprising:
a steering gearbox;
a left-hand (LH) tie-rod and a right-hand (RH) tie-rod;
a pair of idler arms connected to the LH tie-rod and the RH tie-rod;
a common T-link connected to the pair of idler arms to drive the LH Tie-rod and the RH Tie-rod;
a pitman arm connected to the steering gearbox to provide motion to the common T-link; and
a steering Tray to provide an inboard mounting for the idler arms, wherein the idler arms rotate the steering tray providing motion to the LH and RH tie-rods of RH and LH wheels of the vehicle.
2. The apparatus of claim 1, wherein the inboard mounting for the idler arms maximizes steering angles and minimizes bump steer.
3. The apparatus of claim 1, wherein the steering tray is mounted on both sides of a chassis of the vehicle using a rigid mounting bracket and facilitates the inboard mounting for the idler arms.
4. The apparatus of claim 2, wherein the idler arms are mounted on the steering tray connected to the LH tie-rod and the RH tie-rod using the rigid mounting brackets.
5. The apparatus of claim 1, wherein the steering tray is equipped with integrated a RH steering lock and a LH steering lock for full LH and RH turns.

6. The apparatus of claim 1, wherein the RH tie-rod arms is connected to RH wheel end to provide steering to the RH wheel and the LH tie-rod arms is connected to LH wheel to provide steering to RH wheel of the vehicle.
7. The apparatus of claim 1, wherein the common T-link connects to the Idler arms to the input through drag link from Pitman arm and tie-rods that connect Idler arms to wheels of the vehicle.
8. The apparatus of claim 1, wherein the idler arms are mounted away from the wheels to increase wheel lock angles without interfering with the idler arms.