FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION SUSPENSION SYSTEM FOR A VEHICLE
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
INVENTORS
Soheb Ahmed, Abhay Deshpande, Umesh Abhyankar & Mandar Hajare
All Indian Nationals
of TATA MOTORS LIMITED an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the
manner in which it is to be performed.

FIELD OF INVENTION
This invention relates to a suspension system for a vehicle and more particularly relates to a suspension of an individual wheel of a vehicle.
BACKGROUND OF INVENTION
The conventional independent rear suspensions system normally uses semi trailing arm suspension. This suspension system comprises of two arms pivoted at an angle to front plane of vehicle and the arms may also be pivoted at an angle to the horizontal plane. This is done in order to achieve desired kinematic behavior from the suspension. The semi trailing arm is secured at the rear end to a hub carrier which carries a rear wheel hub. A vertically extending strut is provided between rear end portion of the semi trailing arm and the vehicle body. It has, however been recognized that these suspensions systems suffer from defects like low lateral rigidity. US 4537420, US 4715615 & US 4815755 have addressed this issue through various means. In addition to the issue of low lateral rigidity, these suspension systems also suffer from issues of low durability and reliability due to mechanical failures at joinery locations between two arms. Additionally problems like geometry distortion during assembly/joining are also seen. Conventionally, the two arms are joined together most commonly by arc welding. Arc welding leads to distortions in the geometry of the suspension which is unacceptable. The joint portion of the two arms is subjected to forces and torques in multiple directions which have to be endured by the welding, which is a concern from durability of the suspension system.
OBJECTS OF INVENTION
The main object of this invention is to provide a suspension system which can provide sufficient lateral rigidity without adding additional parts in order to improve the stability of the vehicle.


Another object of this invention is to provide a suspension system having improved joint between two arms.
Yet another object of this invention is to provide a suspension system which is simple in construction and cost effective.
Yet another object of this invention is to provide a suspension system which is dimensionally accurate in series production.
STATEMENT OF INVENTION
An improved suspension system for a vehicle comprising outer arm, outer arm reinforcement, inner arm, inner arm reinforcement, damper bracket, spring seat and sleeves wherein said outer arm and its reinforcement is joined to inner arm and its reinforcement to form continual joinery between said arms, said spring seat is provided at rear end of said outer and inner arm and front ends of said outer arm and inner arm are provided with said sleeves.
SUMMARY OF INVENTION
The suspension system comprises of two semi trailing arms (outer and inner) and their reinforcements made by conventional stamping process. The shape of the arms and reinforcements is such that it gives improved stiffness in camber and toe. The outer arm and inner arm are assembled with respective reinforcements such that in assembled conditions there is improved joinery between the two. The joining between outer and inner arm and their reinforcements is designed so that there is least distortion which helps in achieving better manufacturing tolerances.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 shows an isometric top view of a suspension system in accordance with this invention.


Figure 2 shows an isometric bottom view of a suspension system in accordance
with this invention
Figure 3 shows an another view of a suspension system in accordance with this
invention
Figure 4 shows isometric view of outer arm subassembly used in this invention
Figure 5 shows isometric view of inner arm subassembly used in this invention
Figure 6 & 7 shows views of outer arm reinforcement used in this invention
DETAILED DESCRIPTION OF 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,
Referring to figs.l to 7, semi trailing arm suspension (1) consists of outer arm (2), outer arm reinforcement (3), inner arm (4), inner arm reinforcement (5), spring seat (7), damper bracket (8) and bush sleeves (13). Wherein the outer arm (2), outer arm reinforcement (3), inner arm (4) and inner arm reinforcement (5) are preferably made of C sections. The outer arm reinforcement (3) is designed such that at one end a bent profile (9) is formed as shown in fig 6 and fig 7. Outer arm (2) and outer arm reinforcement (3) are assembled together with C-in-C type joinery. Similarly, inner arm (4) and inner arm reinforcement (5) are assembled together with C-in-C type joinery. The joinery between outer arm (2) and its reinforcement (3) and inner arm (4) and its reinforcement (5) is by spot welding as shown in fig 4 and fig 5 respectively. Additionally, inner link closing plate (6) is also assembled with inner link (4) by spot welding. Outer arm (2) and reinforcement (3) subassembly is combined with inner arm (4) and reinforcement (5) subassembly such that the outer arm reinforcement (3) bent profile (9) is joined with inner arm reinforcement (5). Alternatively, the assembly can be made by having bent profile on inner arm reinforcement and combining outer arm and its reinforcement subassembly with inner arm and its reinforcement subassembly such that the inner arm reinforcement bent profile is


joined with outer arm reinforcement. Spring seat (7) has two side walls (14, 15) and top surface (16), which is either an integrated unit or multiple parts joined together. Damper bracket (8) is welded to inner arm (4) and has an undercut (19) as shown in fig.2. Hose bracket (12) is fitted on inner arm(4). Two sleeves (13) are respectively welded to outer arm (2) and inner arm (4) at end. Spring seat (7) is welded to both outer arm (2) and inner arm (4). Outer arm (2) has axle hub mounting holes (17) and depression (18) which is shown in fig. 4. Axle and wheel assembly is fitted on the hub mounting holes (17). The suspension assembly is mounted on the vehicle body by fastening the bush sleeves (13) with isolators to the vehicle body side brackets.
During vehicle running on rough roads various forces act on suspension. In case of semi trailing arm suspension (1) these forces act on the pivot centers, hub end and damper mounting point. The twisting forces have to be endured by the joint between the two suspension arms. In accordance with this invention, outer arm (2) and inner arm (4) subassemblies are assembled such that the bent profile (9) in outer arm reinforcement (3) is joined with inner arm reinforcement (5) by welding process thus creating a continual joinery between outer arm (2), outer arm reinforcement (3) and inner arm (4).
When multi direction twisting forces are exerted at the suspension during vehicle driving the continual joinery design of semi trailing arm endures the loads, not only improving the durability of the suspension system but also increasing rigidity. The depression in outer arm helps in improving stiffness in lateral direction and inner arm closing plate improves stiffness under vertical loads of the suspension. Additionally, since the joinery design between outer arm and its reinforcement as well as between inner arm and its reinforcement facilitates spot welding instead of conventional arc welding the heat generated distortions are minimal. This helps in achieving improved dimensional accuracy and repeatability of the suspension system in series production.


The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous 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.


WE CLAIM
1. An improved suspension system for a vehicle comprising outer arm, outer arm reinforcement, inner arm, inner arm reinforcement, damper bracket, spring seat and sleeves wherein said outer arm and its reinforcement is joined to inner arm and its reinforcement to form continual joinery between said arms, said spring seat is provided at rear end of said outer and inner arm and front ends of said outer arm and inner arm are provided with said sleeves.
2. An improved suspension system for a vehicle as claimed in claim 1 wherein said outer arm reinforcement is provided with bent profile at one end so as to have a surface contact with inner arm reinforcement for better strength and stiffness.
3. An improved suspension system for a vehicle as claimed in claim 1 wherein said inner arm reinforcement is provided with bent profile at one end so as to have a surface contact with outer arm reinforcement for better strength and stiffness.
4. An improved suspension system for a vehicle as claimed in claims 1 to 3 wherein said outer arm and its reinforcement are joined together by a C-in-C spot weld joinery and inner arm and its reinforcement are joined together by a C-in-C spot weld joinery.
5. Suspension system as claimed in claims 1 to 4 wherein said outer arm has curvilinear profile to have clearance with tyre of vehicle.
6. Suspension system as claimed in claims 1 to 5 wherein said damper bracket is provided with undercut at the bend portion.

7. Suspension system as claimed in claims 1 to 6 wherein said spring seat has two side walls and top surface, which is either an integrated unit or multiple parts joined together.
8. Suspension system as claimed in claims 1 to 7 wherein one side wall of spring seat is fitted to inner arm and other side wall and top surface are fitted to outer arm.
9. Vehicle fitted with suspension system as claimed in claims 1 to 8 wherein bush sleeves are fitted onto vehicle body and rear end is fitted with wheel hub.
10. An improved suspension system for a vehicle substantially as herein described with reference to accompanying drawings.

ABSTRACT
SUSPENSION SYSTEM FOR A VEHICLE
This invention relates to a suspension system for a vehicle, which comprises of outer arm, inner arm and their reinforcements. The shape of the arms and reinforcements is such that it gives improved stiffness in camber and toe. The outer arm and inner arm are assembled with respective reinforcements such that in assembled conditions there is improved joinery between the two. This helps in improving rigidity and durability of the suspension system. The joining between outer and inner arm and their reinforcements is designed so that there is least distortion which helps in achieving better manufacturing tolerances.
Fig.l