FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (See Section 10; rule 13)
TITLE OF THE INVENTION
Hydro-formed front sub-frame for a vehicle APPLICANTS
TATA MOTORS LIMITED, an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutahna Chowk,
Mumbai 400 001 Maharashtra, India
INVENTORS
Mr. Dhairyasheel Prabhakar Salunkhe, Mr, Prasad Bhaskarrao Jadhav, Mr. Jeetendra Prakash Chaudhari & Mr. Manoj Bhagwan More
All Indian national
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 describes the invention and the manner in which it is to be
performed.

Field of invention
This invention relates to front subframe of front suspension of a Vehicle Suspension System for an independent suspension system of a vehicle and more particularly to a hydro formed subframe.
Background of the invention
Sub-frame of a vehicle is a member of front suspension which absorbs and transfers the loads
coming from road to BIW. Subframe typically used for carrying lateral and longitudinal loads
coming from wheels while vertical loads are transferred to strut through stub axle. Typical
architecture of subframe comprises two closed section longitudinal members running parallel to
vehicle longitudinal direction and at least one cross member connecting the two longitudinal
members. The longitudinal member and cross member are typicany manufactured by sheet metal
processes. Due to sheet metal parts, number of components increased thereby increase assembly
cost by welding of these components. The existing systems also have more weight because of its
construction. Also, subframe has four pivot points where the lower control arm is connected
through bushes and four BIW mounting points. In a typical subframe, front BIW mounting
brackets are made from sheet metal processes which incures multi components with high cost
and complex manufacturing process. One of the mounting points of engine is on lateral member.
Engine is connected to C-mount through bush to cross member of a subframe. Load from the
engine in static as well as running condition is distributed to lateral member and vibrations from
the engine are refrained from passenger compartment. At the same time, loads on lateral member
due to engine increases and induces highly localized stresses.
Object:
The main object of the invention is to obviate the above mentic)ned drawbacks.
Another object of the invention is to restructure the support structure to provide stiffness and strength; and reducing weight.
Yet another object of the invention is to provide hydroformed tubular subframe having requisite stiffness and low weight thereby reducing carbon foot print.

Summary:
A Hydro-formed front sub-frame for a vehicle comprising: - a front subframe which is mounted on a vehicle body, said subframe supports lower control arm and anti roll bar of front suspension system, rack and pinion assembly of steering system and a mount of engine, said front subframe having rear subassembly and front subassemblies, said rear subassembly having rigid lateral member, spacers at rear mounts for subframe and spacers for c-mount, said front subframe mounted at its front to long members at its either side at 31, 32 and it is mounted at its rear to the long members at its either side at 33, 34, said subframe is tubular and formed by hydroforming.
The anti roll bar mounting bracket is combined with lower link rear pivot bracket. The steering rack is bolt-ably mounted on said subframe. The C-mounting bracket is provided at bottom side of said subframe and is fastened to C-mount of engine. The front axis of lower link pivot at subframe is horizontal and rear pivot point at subframe is vertical. The flexible connections are provided in subframe to reduce excitations trough engine and vibrations through roads namely engine C-mount to subframe, lower link front and rear pivot. The subassembly 1 is a rigid hollow tubular structure for subframe acts as main load path. The front assembly is formed from C-in-C support channels consisting of upper and lower channel on both left and right side.
The C-in-C section contents subframe horns on either side, brackets for front pivot of lower link on either side and sheet metal for front supporting bracket on either side. The horns act as connection between subframe and front mountings. The lateral member is made up in two offset horizontal planes packaging constrained and said horns are made in such way that it provides material in between said driveshaft and said steering rack. The combination of said tubular butterfly hydroformed shape and said tubular horn provide excellent stiffness while retaining light weight
Brief description

The present invention will be more fully understood by reference to the following detailed description of a preferred embodiment of the present invention when read in conjunction with the accompanying drawing, in which:
FIG. 1 is an elevated perspective view of front subframe with complete assembly, parts, pivots and mounting points are numbered.
FIG. 2 is a detailed drawing of front subframe.
FIG. 3 shows a rear view of front subframe showing a complex shape.
Detailed Description
In instant application, traditional sheet metal longitudinal and cross members are replaced by a single hydroformed closed tubular section. This hydroformed component is easier to manufacture. Also, numbers of components are reduced thereby reducing assembly and fabricating cost for the same. For a vehicle support structure, stated subframe is essential component with tubular butterfly shape provide essential stiffness and strength to the vehicle suspension and engine mounts. This tubular butterfly subframe is an integral body with the lateral member which serves the dual purpose of cross member and support to the anti roll bar and rack and pinion assembly having the rectangular section.
The combination of tubular butterfly hydroformed shape and tubular horn provide excellent stiffness compared to conventional sheet metal construction while retaining light weight.
In the existing proposals there is always a trade off between reducing the weight of the front suspension subframe and increase the stiffness. Though there have been few cases of reduction in weight achieved with sheet metal architecture, nevertheless stiffness of the subframe needs to be increased to withstand against the higher loads, this need usually comes when the same design of the subframe has to be used for vehicle with higher weight.
To fulfill such a requirement, either additional reinforcement is used or thickness of the components are increased which again leads to higher weight. These necessary changes require a

lot of design efforts and testing cycles, assembly of different components, increase in assembly efforts and time which adds to the cost of the part.
In instant application, traditional sheet metal longitudinal and cross members are replaced by a single hydroformed closed tubular section. This hydroformed component is easier to manufacture. Also, numbers of components are reduced thereby reducing assembly and fabricating cost for the same. For a vehicle support structure, stated subframe is essential component with tubular butterfly shape provide essential stiffness and strength to the vehicle suspension and engine mounts. This tubular butterfly subframe is an integral body with the lateral member which serves the dual purpose of cross member and support to the anti roll bar and rack and pinion assembly having the rectangular section.
Current design replaces traditional sheet metal parts which incurs high cost while manufacturing by tubular horns. Unlike the prior arts tubular horns require only one bending operation and are easy to manufacture and assemble.
Overall this combination of tubular butterfly hydroformed shape and tubular horn provide excellent stiffness compared to conventional sheet metal construction while retaining light weight.
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 shows a front subframe which is mounted on a vehicle body (not shown in the drawing) and supports the lower control arm and anti roll bar of front suspension system, rack and pinion assembly of steering system and one of the mount of engine. The front subframe comprises rear subassembly 1 and front subassemblies 2, 3. The rear subassembly 1 comprises rigid lateral member 4, spacers at rear mounts for subframe 5, 6 and spacers for c-mount 41. The front subframe is mounted at its front to the long members at its either side at 31, 32 and it is mounted at its rear to the long members at its either side at 33, 34.

To reduce the material and manufacturing process steps anti roll bar mounting bracket is combined with lower link rear pivot bracket 17, 18. Anti roll bar (not shown in Fig. 1) is mounted on this bracket with the help of two-plus-two mounting bolts 42, 43 on either side. The steering rack is mounted on the subframe with the help of single bolt (not shown in Fig.) at 39, 40. C-mounting bracket is provided at bottom side of the subframe and C-mount of engine is connected with subframe and C-mounting bracket by means of single bolt at the center (not shown in Fig 1). Lower link (not shown in Fig 1) is connected with subframe at front (35, 36) and rear pivot (37, 38) points with help of rubber bushes in between subframe and pivoting bolts. The front axis of lower link pivot at subframe is horizontal and rear pivot point at subframe is vertical. In an all, three flexible connections provided in subframe to reduce excitations trough engine and vibrations through roads and these connections are: engine C-mount to subframe and lower link front and rear pivot.
Fig. 2 shows that the subassembly 1 forms a rigid structure for subframe and this is the main load path for the subframe load. Subassembly 2, 3 and different components like lower link bracket 17, 18, 19 and c-mounting brackets (not shown in Fig. 1) are attached to this load path.
The front assembly 2 of subframe is formed from the C-in-C support channels 2 which consist of upper and lower channel 7, 8 on right side and same on left side with subassembly 3 which consists of channel 9, 10. This C-in-C section is made in terms of maintaining the section given to lateral member 4. this subassembly 2 contents subframe horns 11, 12 on either side, bracket 13, 14 for front pivot of lower link on either side and sheet metal front supporting bracket 15, 16 on either side to support between C-in-C channel 2, 3 and bracket for front pivot of lower link 35, 36. The horns 11,12 play a vital role in this assembly as they provide connection between subframe and front mountings 31, 32.
There are packaging constrained to provide required material at exact locations. Keeping these constraints in mind there are some structural compromises have been taken like lateral member 4 is made up in two offset horizontal planes as shown in Fig. 3. The horns 11, 12 are made in such way that it provides material in between driveshaft and steering rack.

Advantages:
• New design of subframe consists of a less weighted hydroformed tubular butterfly shape.
• Subframe comprising single hydroformed rectangular section member replacing the traditional longitudinal members and cross members.
• Keeping existing packaging constraint new subframe supports one of the engine mounts, suspension, anti roll bar and steering rack and pinion.
• A single tubular horn easy to manufacture and assemble replacing traditional sheet metal front BIW mounting brackets.
• Front and rear pivot mounting brackets for lower link is having substantial stiffness in vehicle longitudinal, lateral and vertical direction and mechanical strength.
• Engine c mount bracket having comparable stiffness and strength.
• New subframe design comprises four mounting points instead of six in the existing system so it reduces total assembly process.
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.

Claims
We Claim:
1. A Hydro-formed front sub-frame for a vehicle comprising:
- a front subframe which is mounted on a vehicle body,
- said subframe supports lower control arm and anti roll bar of front suspension system, rack and pinion assembly of steering system and a mount of engine,
- said front subframe having rear subassembly and front subassemblies,
- said rear subassembly having rigid lateral member, spacers at rear mounts for subframe and spacers for c-mount,
- said front subframe mounted at its front to long members at its either side at 31, 32 and it is mounted at its rear to the long members at its either side at 33, 34,
- said subframe is tubular in construction and formed by hydroforming.

2. The Hydro-formed front sub-frame for a vehicle as claimed in claim 1 wherein, anti roll bar mounting bracket is combined with lower link rear pivot bracket.
3. The Hydro-formed front sub-frame for a vehicle as claimed in claim 1 wherein, steering rack is bolt-ably mounted on said subframe.
4. The Hydro-formed front sub-frame for a vehicle as claimed in claim 1 wherein, C-mounting bracket is provided at bottom side of said subframe and is fastened to C-mount of engine.
5. The Hydro-formed front sub-frame for a vehicle as claimed in claim 1 wherein, front axis of lower link pivot at subframe is horizontal and rear pivot point at subframe is vertical.
6. The Hydro-formed front sub-frame for a vehicle as claimed in claim 1 wherein, flexible connections are provided in subframe to reduce excitations trough engine and vibrations through roads namely engine C-mount to subframe. lower link front and rear pivot.

7. The Hydro-formed front sub-frame for a vehicle as claimed in claim 1 wherein, subassembly 1 is a rigid hollow tubular structure for subframe acts as main load path.
8. The Hydro-formed front sub-frame for a vehicle as claimed in claim 1 wherein, said front assembly is formed from C-in-C support channels consisting of upper and lower channel on both left and right side.
9. The Hydro-formed front sub-frame for a vehicle as claimed in claim 1 wherein, said C-in-C section contents subframe horns on either side, brackets for front pivot of lower link on either side and sheet metal for front supporting bracket on either side.

10. The Hydro-formed front sub-frame for a vehicle as claimed in claim 1 wherein, said horns act as connection between subframe and front mountings.
11. The Hydro-formed front sub-frame for a vehicle as claimed in claim 1 wherein, said lateral member is made up in two offset horizontal planes packaging constrained and said horns are made in such way that it provides material in between said driveshaft and said steering rack.
12. The Hydro-formed front sub-frame for a vehicle as claimed in claim 1 wherein, combination of said tubular hydroformed butterfly shape and said tubular horn provide excellent stiffness while retaining light weight
13. A Hydro-formed front sub-frame for a vehicle as hereinabove described with reference to the accompanying drawings.