Claims:
1. A method of manufacturing a unibody vehicle body part, said method comprising the following steps:
forming a die assembly including a first die and a second die with protrusions, said die assembly having a body part area and a scrap area, said die assembly configured to form at least one unibody metallic body part;
placing a metal sheet between said first die and said second die;
pressing said first die on said metallic sheet to draw said metallic sheet in X, Y, and Z direction with a uniform drawing depth in a direction of movement of said first die to obtain an intermediate body part sheet, said intermediate body part sheet having a body part and a scrap part with beads configured thereon to avoid wrinkle formation on said body part;
trimming said scrap part to obtain a unibody metallic body part;
cam flanging an angular and flat surface of an operative top portion of said body part;
flanging a vertical edge of said body part; and
cam forming an operative bottom surface of an operative bottom portion of said body part.
2. The method as claimed in claim 1, wherein said body part is selected from the group consisting of a fender, a bonnet, a side door panel, a bumper, a quarter panel, and a hood.
3. The method as claimed in claim 1, wherein the trimming step includes following sub-steps when said die assembly is configured to form right side body part and left side body part:
cutting a middle portion of said intermediate body part sheet to obtain a right side intermediate body part sheet and a left side intermediate body part sheet; and
trimming said right side intermediate body part sheet and said left side body part sheet.
4. The method as claimed in claim 1, wherein the drawing step includes a sub-step of embossing a surface of said intermediate body part sheet, said second surface is orthogonal to the beads.
5. The method as claimed in claim 1, wherein the drawing depth is maintained uniform by drawing an addendum surface on said metallic sheet.
6. The method as claimed in claim 5, wherein said drawing step includes a sub-step of forming a step portion on said addendum surface.
, Description:FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
[See section 10, Rule 13]

A METHOD OF MANUFACTURING A UNIBODY VEHICLE BODY PART

MAHINDRA & MAHINDRA LIMITED, A COMPANY REGISTERED UNDER THE INDIAN COMPANIES ACT, 1913, HAVING ADDRESS AT MAHINDRA RESEARCH VALLEY (MRV), MAHINDRA WORLD CITY, PLOT NO: 41/1, ANJUR P.O., CHENGALPATTU – 603004, KANCHEEPURAM DIST., TAMIL NADU, INDIA

THE FOLLOWING SPECIFICATION DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

TECHNICAL FIELD OF THE INVENTION
The present disclosure relates to methods of manufacturing a unibody vehicle body parts.
BACKGROUND OF THE INVENTION
Conventionally, any vehicle body part is formed by joining two or more sub-parts together. The sub-parts can be made of a metallic material or a plastic material. Depending upon the material used, the sub-parts are either welded or joined to each other using fasteners to form the body part. These sub-parts are manufactured separately, and are then joined to form a particular vehicle body part. Manufacturing of these sub-parts requires distinct dies which adds to the cost. Further, the joinery of such body part is difficult. As the body part is formed by joining two or more sub-parts, the split lines between the joined sub-parts are visible. This hampers the aesthetics of the vehicle. The strength of such body part is low as joints between the adjacent sub-parts are susceptible to failure.
Therefore, there is felt a need of a method that facilitates manufacturing of a unibody vehicle body part.
SUMMARY OF THE INVENTION
The present disclosure envisages a method of manufacturing a unibody vehicle body part. The method comprises the following steps. Initially, a die assembly is provided. The die assembly comprises a first die and a second die with protrusions. The die assembly has a body part area and a scrap area, and is configured to form at least one unibody metallic vehicle body part. A metallic sheet is placed between the first die and the second die. After placing the metallic sheet, the first die is pressed on the second die to draw the metallic sheet in X, Y, and Z direction. The metallic sheet is drawn with a uniform depth in a direction of movement of the first die to obtain an intermediate body part sheet. The intermediate body part sheet has a body part and a scrap part with beads configured thereon. The beads are configured to avoid wrinkle formation on the body part. The scrap part of the sheet is trimmed to obtain a unibody metallic body part. Angular and flat surfaces of an operative top portion of the body part are cam flanged, and vertical edge of the body part is flanged. An operative bottom surface of an operative bottom portion of the body part is cam formed.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWING
A method of manufacturing a unibody vehicle body part will now be described with reference to accompanying drawing, in which:
Figure 1 illustrates an isometric view of a first die;
Figure 2 illustrates an isometric view of a second die;
Figure 3 illustrates a top view of an intermediate body part sheet;
Figure 4 illustrates an isometric view of the intermediate body part sheet;
Figure 5 illustrates another top view of the intermediate body part sheet;
Figure 6 illustrates a schematic view of the intermediate body part sheet depicting a step portion;
Figure 7 illustrates another isometric top view of the intermediate body part sheet;
Figure 8 illustrates another top view of the intermediate body part sheet;
Figure 9, Figure 10, and Figure 11 illustrate schematic views of the intermediate body part sheet depicting various manufacturing stages; and
Figure 12 illustrates an isometric view of a unibody vehicle body part.

LIST OF REFERENCE NUMERLS
60 – First die
65 – Recesses
80 – Second die
85 – Projections
90 – Protrusions
100 – Intermediate body part sheet
110 – Drawing depth
120 – Addendum surface
130 – Body part
140 – Scrap part
145 – Step portion
150 – Beads
160 – First surface
170 – Second surface
180 – Embossed surface
185 – Top portion of body part sheets
188 – Middle portion of the intermediate body part sheet
190 – Right side body part sheet
192 – Left side body part sheet
194 – Bottom portion of the body part sheets
196 – Vertical flange of the body part sheet
198a – Right side body part
198b – Left side body part
200 – Body part
210 – Wheel arch
220 – Slot
DETAILED DESCRIPTION OF THE INVENTION
Although specific terms are used in the following description for sake of clarity, these terms are intended to refer only to particular structure of the invention selected for illustration in the drawings, and are not intended to define or limit the scope of the invention.
References in the specification to “one embodiment” or “an embodiment” mean that a particular feature, structure, characteristic, or function described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.
The present disclosure envisages a method of manufacturing a unibody vehicle body part. The method is now described with reference to Figure 1 to Figure 12.
Initially, a die assembly is provided. The die assembly comprises a first die (60) and a second die (80). The die assembly has a body part area and a scrap area, wherein the body part area corresponds to a body part formed and a scrap area corresponds to a scrap part of the sheet which is trimmed after drawing process. In an embodiment, as shown in Figure 1 and Figure 2, the first die (60) has recesses (65), whereas the second die (80) has projections (85) configured thereon. In another embodiment, the projections are formed on the first die, whereas the recesses are formed on the second die. The recesses (65) and the projections (85) are complementary to each other, and are configured such that when a metallic sheet placed between the first die (60) and the second die (80) is subjected to drawing process, a body part sheet is formed. In an embodiment, the die assembly is configured to form a single unibody vehicle body part. In another embodiment, the die assembly is configured to manufacture two body parts, i.e., a left side body part and a right side body part, simultaneously.
The second die (80) has protrusions (90) formed thereon. The protrusions (80) are formed on the scrap area of the die assembly. The protrusions (80) form beads on the sheet during the drawing process.
A metallic sheet is placed between the first die (60) and the second die (80). Further, the first die (60) is pressed on the second die (80), more specifically on the metallic sheet, to draw the metallic sheet in X, Y, and Z directions to obtain an intermediate body part sheet (100) as shown in Figure 3. Here, X, Y, and Z directions are the directions of axis of Cartesian coordinate system. The intermediate body part sheet has a body part (130) and a scrap part (140). The body part (130) resembles the actual body part, whereas the scrap part (140) is an additional area which needs to be trimmed to obtain the body part.
In an embodiment, instead of the first die (60), the second die (80) is pressed against the metallic sheet. In another embodiment, the first die (60) is an operative upper die, whereas the second die (80) is an operative lower die or vice versa.
The metallic sheet is drawn with a uniform drawing depth in a direction of the movement of the first die (60). The uniform drawing depth is maintained in a direction of movement of the first die (60).
The uniform drawing depth maintained on the metallic sheet while drawing is shown by the reference numeral 110 in Figure 4. The uniform drawing depth maintained throughout the drawing process avoids formability issues like split or excessive thinning of the metallic sheet.
In an embodiment, the uniform drawing depth is maintained by drawing an addendum surface (120) on the metallic sheet. For illustration purpose, the addendum surface (120) is shown on the intermediate body part sheet (100) in Figure 4. The addendum surface (120) is trimmed in a trimming step. More specifically, the addendum surface (120) is an additional surface formed on the metallic sheet to maintain the uniform drawing depth which is further trimmed. The addendum surface (120) can be formed on one or more sides of the metallic sheet depending upon the shape of a body part to be manufactured.
The method further includes a step of forming a step portion (145) on the addendum surface (120). The step portion (145) is formed during the drawing step. The step portion (145) prevents formation of skid-lines or shock-lines and also prevents spring back effect observed at curved surfaces.
The method further includes a step of providing beads (150) on a first surface (160) of the intermediate body part sheet (100). The first surface (160) is a part of the scrap part (140). The beads (150) are formed on the metallic sheet during drawing process. The protrusions (90) of the die assembly are configured to form the beads (150) on the metallic sheet during the drawing process. In another embodiment, the beads (150) are added on the intermediate body part sheet (100).
The beads (150) eliminate the possibility of wrinkle formation on the metallic sheet. The wrinkles are formed at angular surfaces of the sheet due to various stresses developed during the drawing process. The wrinkles hampers aesthetics of the body part formed, and also reduces the strength of the body part at the area where wrinkles are formed. The addition of the beads (150) reduces the amount of stresses developed, and avoids formation of wrinkles.
The method further includes a step of embossing a second surface (170) of the intermediate body part sheet (100). In an embodiment, the second surface (170) is orthogonal to the first surface (160) of the intermediate body part sheet (100) on which the beads (150) are formed. An embossed surface (180) is shown in Figure 8. The embossing eliminates the part stretching issue, and maintains sufficient stretch in the intermediate body part sheet (100). The embossed surface (180) is typically formed on the scrap part (140) of the intermediate body part sheet (100).
The intermediate body part sheet (100) is trimmed to obtain at least one unibody vehicle body part. In an embodiment, the intermediate body part sheet (100) is trimmed to obtain two body parts, i.e., a right side body part and a left side body part of an automobile vehicle.
The scrap part (140) of the intermediate body part sheet (100) is trimmed and the body part (130) is retained. The trimmed surfaces of the intermediate body part sheet (100) are shown by dotted lines in Figures 9, 10 and 11. Particularly, an operative top portion (185) of the intermediate body part sheet (100) is C-trimmed, whereas other portions of the scrap part (140) are trimmed.
When the die assembly is configured to form a right side body part and a left side body part, a middle portion (188) of the intermediate body part sheet (100) is trimmed to obtain a right side intermediate body part sheet (190) and a left side intermediate body part sheet (192) as shown by the dotted lines in Figure 9. The right side intermediate body part sheet (190) and a left side intermediate body part sheet (192) are further trimmed at the scrap part (140).
Cam forming operation is performed on an operative bottom portion (194) of the right and left side body part sheets (190, 192), and cam flanging operation is performed on angular surfaces as well as flat surface of the operative top portions (185) of the right and left side body part sheets (190, 192) (as shown by the dotted lines in Figure 10 and 11) to obtain a right side body part (198a) and a left side body part (198b).
Further, the right side body part (198a) and the left side body part (198b) are pierced at appropriate locations. Typically, the right and left side body parts (198a, 198b) are pierced near vertical flange (196) and at the bottom portion (194) thereof.
In case of single body part forming die, the cam flanging, cam forming, piercing, and vertical edge flanging operations are performed on the single body part sheet obtained from the die assembly.
A body part (200) obtained by the method of the present disclosure is shown in Figure 12. The body part (200) of a vehicle that can be manufactured using the method of the present disclosure is selected from the group consisting of a fender, a bonnet, a side door panel, a bumper, a quarter panel, and a hood.
For illustration purpose, a fender of a vehicle is shown as the body part (200) in accompanying figures. However, any other body part can be manufactured by the manufacturing process of the present disclosure. The fender (200) has a unibody structure and an integral wheel arch (210). The fender (200) has a slot (220) for receiving a headlamp therein. Further, the unibody fender (200) is provided with various interfaces to facilitate connection of the fender (200) with a vehicle. The fender (200) is provided with a pillar interface, a hood interface, a front bumper interface, and a side door interface.
The method is easy to implement, and eliminates the need of multiple dies and additional manpower to manufacture different sub-parts of a vehicle body part. The method facilitates manufacturing of a unibody body part. Thus, it requires a single die assembly. Further, the method also saves material and joinery cost as the body part manufactured has a unibody configuration.
The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others, skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.