FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION
Methodology Of Chassis System Design For Common Platform Approach
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
Mr. Makarand Takle and Mr. Mahesh Joshi
Both are 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
The present invention relates to a method of designing the three different classes of vehicles SUV, Sedan and MPV under a single, common platform. The design is carried out in such a way to keep maximum common parts among these three vehicles. The commonisation of parts is achieved by satisfying the dimensional and functional and performance parameters corresponding to each of the three types of vehicles.
BACKGROUND OF INVENTION
Currently the automobile manufacturers have main idea of sharing of both components and processes among the several products in order to achieve bigger volumes that allow the use of scale economy. But currently the sharing of components is limited to the smaller aggregate level, it is not upto the broad vehicle level.
OBJECTS OF INVENTION
The present invention provides basis for designing the three classes of vehicles SUV, Sedan and MPV under a common platform with the maximum common parts among these three vehicles. With this design a common assembly line can be used with ease for production of these three vehicles, in turn this will minimize the total development and production cost of these three vehicles.
STATEMENT OF INVENTION
Accordingly the present invention provides a common chassis system designed for
all MPV, SUV and Sedan type of vehicles under a single platform for using
maximum commonised parts comprising
SUV chassis system is adapted as the basic chassis system for producing the
corresponding MPV and Sedan chassis system;
atleast one pair of attachment spacers configured to be placed between the
2

BIW (Body In White) front end and front sub frame for vehicle floor height
variation;
atleast one offset hole configured on said attachment spacers each to accommodate
same BIW front end for specifying/compromising different vehicle widths;
atleast one front joinery means of suitable size adapted to join the two cut ends of
the front cross member of hydroform piece of front sub-frame and atleast two rear
joinery means of suitable sizes adapted to join the two cut ends of the rear
transverse/cross members of rear sub-frame for specifying/compromising different
vehicle widths.
BRIEF DESCRIPTION OF INVENTION
The present invention relates to the method of commonisation of the chassis system and BIW components for the platform of three vehicles namely SUV, Sedan and MPV. The list of commonised parts includes suspension links, suspension mounting subframe, steering system, controls and BIW front end along with the firewall. These parts are commonised among these platform of three vehicles namely SUV, Sedan and MPV in such a way to achieve the overall dimensions of these three vehicles. These three vehicles will have different overall dimensions. This invention describes the procedure for designing the three class of vehicles "SUV", "Sedan" and "MPV" under a single common platform by commonizing the maximum components by achieving the basic overall dimensions of these vehicles by respecting the class of the vehicle from which they belong to. Thus this will reduce the variety and complexity of parts among these vehicles and in turn increase the volume of the parts and reduce the cost of manufacturing these parts.
A method for designing the three different classes of vehicles namely SUV, Sedan, and MPV under a single, common platform. The meaning of single platform is that these three vehicles use a maximum number of common parts and a common assembly line. There is no need to develop three different set of parts for these three vehicles. The vital common part includes suspension links, subframe, steering

system, control assemblies, front BIW structure.
These three different classes of vehicles (SUV/ Sedan / MPV) will be having different widths, lengths and heights according to the market and styling requirements from these vehicles. Also there will be differences in the tyre sizes for these three classes of vehicles e.g. 17", 16" and 15" respectively. By keeping in mind the all expectations from these classes of vehicles the strategy for communizing the above mentioned parts is decided to keep maximum possible common parts between these three vehicles.
The common chassis system with attachment spacers provided with offset hole alongwith front joinery means of suitable size and rear joinery means of suitable sizes together customizes a common chassis system for all MPV, SUV and Sedan type of vehicles under a single platform for using maximum commonised parts by specifying / compromising different vehicle widths. The common parts strategy and design of these parts is also decided in such way that the entire vehicle level parameters i.e. suspension kinematics and geometry are achieved in this process.
BRIEF DESCRIPTION OF DRAWINGS
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 view of "SUV" showing BIW front end, front subframe and
front suspension components.
FIG 2: shows a plan view of "SUV" showing BIW front end, front subframe and
front suspension components.
FIG 3: shows a side view of "SUV" showing BIW front end, front subframe and
front suspension components.
FIG 4: shows a front view of "Sedan" showing BIW front end, front subframe and
front suspension components.

FIG 5: shows a plan view of "Sedan" showing BIW front end, front sub frame and
front suspension components.
FIG 6: shows a side view of "Sedan" showing BIW front end, front subframe and
front suspension components.
FIG 7: shows a front view of "SUV" showing rear subframe and rear suspension
components.
FIG 8: shows a top view of "SUV" showing rear subframe and rear suspension
components.
FIG 9: shows a front view of "Sedan" showing rear subframe and rear suspension
components.
FIG 10: shows a top view of "Sedan" showing rear subframe and rear suspension
components.
DETAILED DESCRIPTION OF INVENTION
Referring now to the drawings and particularly to the FIGS. 1, 2 and 3, there is illustrated an automotive vehicle known as "SUV". The typical "SUV" is designed with the 17" tyre 1 which is having high static radius than a 16" inch tyre. The BIW front end 2 along with the BIW crash member 3 and firewall 4 are as shown in FIG 3. This BIW front end 2 is attached with the front subframe 5 with a pair of attachment spacers 13 as shown in the FIG2 and FIG 3. This pair of attachment spacers 13 of front subframe 5 with the BIW front end 2 can be changed to achieve the different height of front BIW floor 12 from the ground. Also this spacer with an offset hole along transverse direction of the vehicle is used to accommodate the same BIW front end 2 to achieve the different vehicle widths. This technique can be used to achieve different floor heights and widths for "Sedan" and "MPV" class of vehicles. The 17" tyre 1 is connected to BIW front end 2 through steering knuckle 6 and front suspension strut 7 from one side and to front subframe 5 through front suspension lower link 8. With this construction and attachment point's front part of the "SUV" is defined. The front wheel track of the vehicle is being fixed by choosing the length of cross member 9 of the front subframe 5

and length of front suspension lower link 8. The floor height of the vehicle is fixed by choosing the height of the attachment member between front subframe 5 and BIW front end 2. Various pairs of said attachment spacers with different heights can be adapted for height variation and for achieving specific BIW floor height from the ground in the vehicles as per different vehicle models.
With this information about the front suspension and front BIW attachment construction of "SUV" , front end for "Sedan" class of vehicle is constructed by commonizing the BIW front end 2, front subframe 5 and front suspension lower links 8. Referring now to the drawings and particularly to the FIGS. 4, 5 and 6, this typical "Sedan" is designed with the 16" tyre (11) which is having lesser static radius than 17" tyre (1) used in the "SUV". Here the invention is to use the same BIW front end 2, front subframe 5 and front suspension lower links 8 from "SUV" to "Sedan". Due to the reduction in the static radius of the tyre for "Sedan", the relation between the floor and ground changes. Also the "Sedan" class of vehicles will demand the lower sitting posture of driver than the "SUV" class of vehicles. To facilitate the lower sitting posture of the driver for "Sedan" the front BIW floor 12 should be lowered along with the BIW front end 2. This is achieved in this invention by using as separate pair of attachment spacers 14. This pair of attachment spacers 14 for "Sedan" is smaller in height and larger in width than the pair of attachment spacer 13 for "SUV". Also this pair of attachment spacers 14 will have provision of offset hole in transverse direction to achieve the smaller width for "Sedan" and to keep same BIW front end 2. With this the same BIW front end 2 is used for "SUV" and "Sedan" and difference in tyre sizes, floor heights and vehicle widths is accommodated by using different heights and widths of spacer attachments. Here the front suspension strut 7 for "SUV" is same as that of the front suspension strut 7 for "Sedan". But the inclinations of the struts as assembled on the vehicle are different for the "SUV" and "Sedan". This is required to accommodate the difference in the heights of "SUV" and "Sedan" and use the

same BIW front end 2.
Another difference between the "Sedan" from "SUV" is that their difference in the front wheel track. Typically this difference in the front track between "SUV" and "Sedan" is not more than 40mm. The "Sedan" front track is typically less than the "SUV" front track. This difference in the front wheel track is achieved by cutting the cross member 9 of hydroform piece of front subframe 5 at the middle and attach them by a joinery means/piece 16 of appropriate size and length. This will keep the front subframe 5 still common between the "SUV" and "Sedan" by adding the suitable front joinery means/piece 16 of suitable size and length to achieve the desired wheel track for "Sedan". While deciding this conversion of "SUV" to "Sedan" by use of the commonisation strategy the kinematics parameters are checked for both the vehicles, this help in deciding the pivot points of the suspension system. The kinematics parameters are namely caster, camber, kingpin inclination, toe change, camber change, wheel track change, roll centre height etc. These kinematics parameters are dependent on the suspensions pivot points also called as hard points. Once the suspension pivot points are finalised, the above mentioned kinematics parameters can be found out. This will play a very vital role in design and commonisation parts between these vehicles. The other parts that can be kept common between the "SUV" and "Sedan" are rack and pinion 17, steering column and control assemblies. These parts are commonised based on the fact that BIW front end 2 is same between the "SUV" and "Sedan".
Rack and pinion, steering column and control assemblies are mounted on the BIW front end 2. As BIW front end 2 is same, the above mentioned parts which are mounted on different areas of the BIW front end 2 will also remains same because the packaging space also remains same.
The same approach as above is used to design the "MPV" class of vehicle from the "SUV" platform. The difference is in the height and width of the attachment spacer and width of subframe joinery piece to achieve the required overall width and

height of "MPV". The rest of the parts will remain same as that of the "SUV" and "Sedan". This invention gives the opportunity of using maximum number of common parts among the three "SUV", "Sedan" and "MPV" class of vehicles. This will reduce the parts variety and complexity between these vehicles. This will also increase the volume of the parts due the commonisation and in turn the cost of the component. This also helps in using a common production line for "SUV", "Sedan" and "MPV" with minimum complexity.
Referring to the FIGS 7 and 8 which illustrates the rear suspension for "SUV" along with the rear subframe 18. 17" tyre 1 is connected to rear subframe 18 through suspension links. There are four such suspension links named upper lateral link 19, lower lateral link 20, toe control link 21 and longitudinal link 22. The rear wheel track for "SUV" is determined by the lengths of the suspension links and length of the rear subframe 18 in transverse direction.
Referring to the FIGS 9 and 10 which illustrates the rear suspension for "Sedan" along with the rear subframe 18. Here the invention is that the 16" tyre 11 is connected to rear subframe 18 through same suspension links as in the "SUV" vehicle. The reduction in the wheel track of the "Sedan" is achieved by cutting the transverse/cross members of the "SUV" rear subframe 18 by suitable amount required for reduction of the rear wheel track and by adding the transverse rear joinery means/members 23, 24 of suitable size and length. The required kinematic properties of rear suspension for "SUV" and "Sedan" are fixed by selecting the optimum pivot locations of rear suspension links of rear subframe 18 and on rear knuckle. This strategy for rear suspension gives the maximum possible parts between "SUV" and "Sedan". The same philosophy is used to design the rear suspension for "MPV".
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 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. Common chassis system designed for all MPV, SUV and Sedan type of vehicles under a single platform for using maximum commonised parts comprising
SUV chassis system is adapted as the basic chassis system for producing the corresponding MPV and Sedan chassis system;
atleast one pair of attachment spacers configured to be placed between the BIW (Body In White) front end and front sub frame for vehicle floor height variation;
atleast one offset hole configured on said attachment spacers each to accommodate same BIW front end for specifying/compromising different vehicle widths;
atleast one front joinery means of suitable size adapted to join the two cut ends of the front cross member of hydroform piece of front sub-frame and atleast two rear joinery means of suitable sizes adapted to join the two cut ends of the rear transverse/cross members of rear sub-frame for specifying/compromising different vehicle widths.
2. The common chassis system as claimed in claim 1, wherein said front wheel track of the vehicle is configured by selecting the respective length of the cross member of the front sub frame and the length of front suspension lower link.
3. The common chassis system as claimed in claim 1, wherein various pairs of said attachment spacers with different heights are adapted for height variation and for achieving specific BIW floor height from the ground in the vehicles as per different vehicle models.
4. The common chassis system as claimed in claim 1, wherein said attachment spacers are adapted for achieving specific lower sitting posture of the driver for

Sedan class of vehicle.
5. The common chassis system as claimed in claim 1, wherein said front joinery means of suitable size and length are adapted to join the two cut ends at middle of said front cross member to achieve the desired wheel track for the selected type of vehicle.
6. The common chassis system as claimed in claim 1, wherein said rear joinery means of suitable size and length are adapted to join the two cut ends at middle of said rear transverse/cross members of rear sub-frame to achieve the desired wheel track for the selected type of vehicle.
7. The common chassis system as claimed in claim 1, wherein said attachment spacers provided with offset hole alongwith said front joinery means of suitable size and said rear joinery means of suitable sizes together customizes a common chassis system for all MPV, SUV and Sedan type of vehicles under a single platform for using maximum commonised parts by specifying / compromising different vehicle widths.
8. The common chassis system as claimed in claim 1, wherein the pivot points of the suspension system of the vehicle are achieved by checking the kinematics parameters of the respective vehicle.
9. The common chassis system as claimed in claim 1, constitute the parts like rack and pinion, steering column and control assemblies as common for all above types of vehicles.

10. Common chassis system designed for all MPV, SUV and Sedan type of vehicles substantially as hereinabove described is with reference to the accompanying drawings.