FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, rule 13]
TITLE OF THE INVENTION "STEERING SYSTEM FOR A VEHICLE"
APPLICANT
TATA MOTORS LIMITED, an Indian company
having its registered office at
Bombay house, 24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001, Maharashtra, INDIA
INVENTORS
Dr Nikolaos Mantikas, A Greek National
and
Mr. Paul J Hillman, A British national
of Tata Motors European Technical Central plc
4th Floor International Automotive Research Centre
University of Warwick Coventry,
CV4 7AL
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed.

TECHNICAL FIELD
The present invention generally relates to steering systems for automotive vehicles, and more particularly it relates to a steering assembly system for an automotive vehicle having 'zero-turn' or 'near zero-turn' maneuvering capabilities.
BACKGROUND OF THE INVENTION
Automotive vehicles, such as cars, typically comprise an engine, a transmission suitably connecting the engine to driving wheels, and a set of steerable wheels. The steerable wheels are controlled by a steering wheel provided adjacent to the driver's seat. The maneuvering of the steering wheel moves the pair of steerable front wheels, thereby maneuvering the vehicle.
The vehicles are often required to be maneuvered in a congested environment, for example, during parking. Designers, therefore, strive to reduce the turning circle of a vehicle, balancing this with the constraining features of package and system geometry to ensure competitive comfort, safety, steering, ride and handling performance, however, hitherto, with limited success.
For conventional passenger car applications there are a number of aspects which restrict the design freedom for zero turn geometries, particularly: Drive line layout and orientation, Ergonomic package (including controls), Suspension and Steering geometry, and Vehicle Safety performance.
Front steering and wheel geometry, facilitating zero turn maneuvers, has been seen in off highway, slow moving vehicles. However, in these instances, a non-suspended rigid axle configuration is incorporated as opposed to independent suspension or suspended axle configuration.

OBJECTS OF THE INVENTION
The objective of invention is to provide a reliable, simple and cost effective, steering system.
Another objective of the invention is to allow a passenger vehicle with independent front suspension to rotate within the track of the rear axle.
Yet another of the invention is to provide steering system that enables zero turn of the vehicle without ignoring the key performance aspects of ride, handling, steering and the like.
Further objects and features of the invention will become apparent from the following detailed description when considered in conjunction with the drawings.
SUMMARY OF THE INVENTION
The various embodiments of the present invention disclose a steering system for a vehicle. The steering system comprising at least one steerable wheel mounted on a wheel hub, the at least one wheel is steerable by means of a gear set assembly connected to a steering mechanism of the vehicle, wherein the wheel hub is mounted on a steering pivot shaft. The gear set assembly further comprises a plurality of meshed gears having an input gear mechanically coupled to the steering mechanism and an output gear integrally connected to the steering pivot, such that the steering rotation from the steering mechanism is transferred to the steerable wheel through the plurality of meshed gears. In an embodiment of the present invention the input gear and steering pivot shaft are supported on an independent wheel suspension.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a perspective view of a steering system, according to an embodiment of the invention, and

FIG. 2A, 2B, and 2C illustrate various top views of a portion of the steering system of FIG. 1, according to an embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same.
FIG. 1 illustrates a perspective view of a steering system 100, according to an embodiment of the invention. The steering system 100 (also referred "steering module 100") is to be used for steering wheels of a vehicle which may be a car, an SUV (Sports Utility Vehicle), a commercial vehicle, or any other automobile, without deviating from the spirit of the invention. The vehicle, as would be apparent to those skilled in the art, includes a body (or frame/sub-frame) carrying a set of wheels, a prime mover driving the wheels, a steering wheel and other vehicle components. The set of wheels support the vehicle of a surface and typically are powered by the prime mover through a transmission system for moving the vehicle on a surface, such as a road. Further, the rotatable steering wheel 116 is mechanically linked with a steerable wheel, and the rotation of the steering wheel turns the wheel, thereby maneuvering the vehicle (Refer Fig 2a). The steerable wheel may be on the front axle of the vehicle. However, the steerable wheel may alternatively be on rear axle (or on both axles), without deviating from the spirit of the present invention.
Referring again to FIG. 1 and Fig 2a, a steering rack 117 is coupled with the steering wheel 116. The steering rack 117 is configured to move laterally with rotation of the steering wheel through a rack and pinion arrangement. In an alternative embodiment of the invention, the steering rack 117 may be replaced with a steering gear box, which may be configures to receive rotational input from the steering wheel. A tie rod 118 is connected with the steering rack 117 and move with the movement of the steering rack 117. The tie rod 118 is configured to

transfer such movement to the steerable wheel through a rotation transfer mechanism.
The rotation transfer mechanism includes a gear set assembly 122 supported on an independent suspension system 101 for the steerable wheel. The movement from the tie rod 118 to the wheel passes through the gear set assembly 122. In one embodiment of the present invention, the gear set assembly 122 includes at least two gears, meshed to transfer rotational motion. A first gear 130 of the gear set assembly 122 is connected to the tie rod and a second gear 132 of the gear set assembly is mechanically connected to the wheel hub.
In such an embodiment, the gear set includes a first gear, such as the first gear 130 and a second gear such as the second gear 132. The first gear 130 is connected to an end portion of the tie rod 118, and is rotatably mounted on the suspension system 101 of the steerable wheel. The first gear 130 is meshed with the second gear 132. More specifically, a toothed peripheral portion of the first gear 130 is engaged with a toothed peripheral portion of the second gear 132. The second gear 132 is integrally mounted on a pivot shaft 108 supported on the suspension system and connected to a wheel hub 106.
In accordance to an embodiment of the present invention, the independent suspension system 101 of the steerable wheel supports the gear seat assembly 122. The suspension system includes an upright member 102 with an integrated pivot sleeve 110. A damper unit 104 is rigidly mounted on the upright member 110. The damper unit 104 may include a damper having a spring 103 coaxially mounted thereon. In an embodiment of the present invention, the spring may be mounted coaxially with the damper but could be offset to counter any damper side force. Alternatively, a control arm can be incorporated; the damper then would no longer be part of the assembly. A first end portion of the damper unit 104, as mentioned earlier, is connected with the upright member 102, while the second end portion of a damper unit 104 may be connected to the vehicle body via a bush (not numbered).

In an embodiment of the present invention, the input gear 130 is mounted at lower mounting portion of the damper unit with the upright member 102 and rotate about the axis of the damper. The input gear has a through hole to accept the damper unit and may be mounted directly on the upright member 102 or on the damper 104. The integrated pivot sleeve 110 has a vertical imaginary axis parallel and offset to the axis of the damper unit 104.
A lower control arm 105 connected at the lower end of the upright member 102. The upright member 102 is locked via a bush 107 onto the lower control arm 105 permitting large rotation about the bush axis only, allowing for suspension bump and rebound travel. The lower control arm 105 is mounted to the body (or frame/sub-frame) via two bushes, the orientation of which can be tuned depending on requirements. The lower control arm 105 is uniquely profiled to allow a wheel angular span of approximately 180 degree with facility for over 105 degree for the in-board rotation.
A wheel hub 106 is mounted on the steering pivot shaft 108 and the hub is free to rotate about the pivot shaft, as shown in FIG 1. Particularly, a steering pivot shaft 108 is received in the sleeve portion 110 of the upright member 102. The rotation of the steering pivot shaft 108 within the sleeve portion is provisioned via bearings. The lower portion of the pivot shaft 108 is extended laterally to mount the wheel hub 106. The lateral extension also facilitates mounting necessary braking arrangements for the wheel hub. The wheel hub 106 is configured to removably hold the wheel, in a known manner.
In an embodiment of the invention the output gear 132 may be mounted on the steering pivot shaft 108 supported on the pivot sleeve 110. The pivot sleeve 110 axis is parallel and offset from the axis of the damper unit 104. The pivot shaft 108 is supported on the pivot sleeve 110 and is adapted to rotate within the sleeve about an axis parallel and offset from the axis of the damper unit 104. Further the pivot shaft vertical axis is offset from the axis of the wheel vertical axis.

Referring to Fig 1, in an embodiment of present invention, the steering wheel is mechanically linked with a pair of steerable wheels, and the rotation of the steering wheel turns the pair of wheels, thereby maneuvering the vehicle. A pair of tie rods, a first tie rod 118 and a second tie rod 118', is connected with the steering rack 117. Because of which, each of the first tie rod 118 and the second tie rod 118' also move with the movement of the steering rack 117. The first tie rod 118 and the second tie rod 118' are configured to transfer such movement to respective wheels through a rotation transfer mechanism as described above.
The ratio between the input gears (130) and output gears (132), together with the position of the tie rod end on the input gear, can be adjusted to provide different steering characteristics. The steering pivot axis (centre for wheel rotation) is offset and parallel to the damper axis to facilitate approximately 180 degree wheel rotation about the lower control arms which in itself is designed to facilitate this wheel rotation. The steering module 100 may further include an anti-roll bar 138 attached onto the lower control arms, but can equally be mounted on the upright or damper unit.
As shown in FIG 2, during the operation of the steering module 100 of vehicle i.e. rotation of the steering wheel, the movement of the tie rod 118 rotates the first gear 130. Because of the toothed meshing of the first gear 130 with the second gear 132, the rotation of the first gear 130 also rotates the second gear 132. The second gear 132 rotates in an opposite direction, because of the meshing with the first gear 130, and about an imaginary vertical longitudinal axis on the pivot shaft 108 of the wheel hub 106. The steering module 100 delivers Ackerman steering and tunable independent suspension properties; typical of passenger car automotive applications.
Referring to fig 2, fig 2a, 2b and 2c show the system for wheel positions, straight ahead; full left lock and full right lock respectively.

In one embodiment of the present invention the steering rack is configured to move left side with anti-clockwise rotation of the steering wheel, eventually rotates the wheel carried by the first wheel hub 106 anti-clockwise direction, thereby enabling the turning of the vehicle in left direction. In other embodiments of the present invention, the steering rack moves right side with clockwise rotation of the steering wheel may eventually rotate the first wheel carried by the first wheel hub 106 and the second wheel carried by the second wheel hub 106 in a clockwise direction thereby enabling the turning of the vehicle in right direction.
The foregoing description provides specific embodiments of the present invention. It should be appreciated that these embodiment are described for purpose of illustration only, and that numerous other alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

Referral Numerals Description
100 Steering system, Steering module
101 Suspension system
102 Upright member
103 Spring
104 Damper unit
105 Lower control arm
106 Wheel hub
108 Steering pivot shaft
110 Sleeve portion
116 Steering Wheel
117 Steering rack
118, 118' Tie rod

122
Gear set assembly
130 First gear
132 Second gear
138 Anti-roll bar

WE CLAIM
1. A steering system for a vehicle comprising;
at least one steerable wheel mounted on a wheel hub, the at least one wheel is steerable by means of a gear set assembly connected to a steering mechanism of the vehicle,
wherein the wheel hub is mounted on a steering pivot shaft,
wherein the gear set assembly further comprises a plurality of meshed gears having an input gear mechanically coupled to the steering mechanism and an output gear integrally connected to the steering pivot shaft.
2. The steering system as claimed in claim 1 wherein the input gear and the steering pivot shaft are rotatably mounted on an independent wheel suspension system.
3. The steering system as claimed in claim 2 wherein the suspension system further comprises an upright member with an integrated pivot sleeve for supporting the steering pivot shaft, a damper unit rigidly mounted on the upright member, and a lower control arm hingedly connected at a lower end of the upright member.
4. The steering system as claimed in claim 3 wherein the input gear is adapted to be rotated about the axis of the damper unit.
5. The steering system as claimed in claim 3 wherein the sleeve axis is parallel and offset from the axis of the damper unit.
6. The steering system as claimed in any preceding claim wherein the pivot shaft supported on the pivot sleeve and is adapted to rotate within the sleeve about an axis parallel and offset from the axis of the damper unit.
7. The steering system as claimed in claim 1 wherein the steering mechanism comprises of a steering wheel mounted on a steering column, the column connected to a steering rack and pinion, and at least a tie rod connected to the steering rack.

8. The steering system as claimed in claim 1 wherein the steering mechanism comprises of a steering wheel mounted on a steering column coupled to a steering gear and at least a tie rod connected to the steering gear.
9. The steering system as claimed in any preceding claim wherein the tie rod is connected to the input gear of the gear set assembly.
10. The steering system as claimed in claim 3 wherein the lower control arm mounted on body of the vehicle.
11. The steering system as claimed in any preceding claim wherein the pivot shaft lowering portion is extended laterally to mount the wheel hub.
12. The steering system as claimed in any preceding claim wherein the gears are sector gears.
13. The steering system as claimed in claim in any preceding claim wherein a pair of wheels steerable by respective gear set assembly connected to the steering mechanism.
14. An automobile having a steering system as claimed in any of claims 1 to 13.