FORM 2
THE PATENT ACT, 1970,
(39 OF 1970)
&
THE PATENTS RULE, 2003
COMPLETE SPECIFICATION
(SEE SECTION 10; RULE 13)
"LADDER HONEYCOMB HOOD STRUCTURE FOR A MOTOR VEHICLE FOR PEDESTRIAN PROTECTION"
MAHINDRA & MAHINDRA LIMITED
AN INDIAN COMPANY,
R&D CENTER, AUTOMOTIVE SECTOR,
89, M.I.D.C, SATPUR,
NASHIK-422 007,
MAHARASHTRA, INDIA.
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES AND ASCERTAINS THE NATURE OF THIS INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

FIELD OF INVENTION:-
The present invention is related to vehicle hood structure. More particularly the present invention is related to hood inner structure having deformable head impact zone and used in automobile vehicle and like other vehicles that protects the pedestrian at the time of impact.
BACKGROUND OF THE PRESENT INVENTION:-
Accident investigations revealed that almost two thirds of the 1.2 million people killed in road traffic crashes worldwide are pedestrians. Pedestrian safety is now high profiles issue within the automotive industry to compliance the safety stringent legislations (Regulation 78/2009 and Euro NCAP). The motive of our work is to design the bonnet which meets EORO NCAP pedestrian legislation requirements.
OEMs throughout the world use expensive materials like Aluminium and expensive techniques like Pop up Hood and air bags to bring down HPC value and offer pedestrian safety. Most of the Vehicles rated above 3 star using Aluminium or Pop up kind of technology to bring down the HPC Value. However, the present invention uses conventional steel panel with Ladder honeycomb structure concept to meet pedestrian safety related regulations. Few OEMs are using honeycomb structure but not using ladder structure which helps in energy absorption and controlled deformation at the center.
Most of the vehicle bonnets include a generally planar or curvilinear outer skin which is joined to a series of reinforcing ribs provided by a stamped metallic sheet of material. During vehicle and pedestrian collision, it is observed that the pedestrian is seriously injured due to the pedestrian's head striking the bonnet of the vehicle. To keep the risk of injury as low as possible, controlled resilience in the head impact region of the bonnet is required. The present invention addresses this problem and provides the novel inner hood structure

that will protect the pedestrian in case of pedestrian impact by absorbing the impact energy.
OBJECTIVES OF THE PRESENT INVENTION:-
The main objective of the present invention is to provide vehicle hood inner structure for pedestrian protection.
Another objective of the present invention is to provide vehicle hood inner structure with honeycomb ladder having a definite cut outs for pedestrian protection.
Another objective of the present invention is to provide vehicle hood inner structure for pedestrian protection wherein head impact energy is absorbed by the honeycomb ladder structure by undergoing deformation.
STATEMENT OF INVENTION:-
Accordingly the invention provides the ladder honeycomb hood structure for a motor vehicle for pedestrian protection comprising an inner panel having ten numbers of complete equally sized Hexagonal of equal diameter cut out with on side making 10° to the horizontal; a first Central ladder cutout formed with horizontal rib; a second Central ladder cutout formed with smaller length of horizontal rib than that of first ladder above the said first central ladder; a third Central ladder cutout formed below the said first central ladder with horizontal rib, merged with rear channel, having bigger length than that of the said first central ladder; the said hood structure an arrangement made in such a way that the said hexagonal cut outs equally formed on both side of said central ladder; and a number of unequal size hexagonal cut out formed in the space between said equal size hexagons and hood side section.

BRIEF DESCRIPTION OF THE FIGURES:-
The invention will become more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, wherein
Figure 1 shows the top view of the honeycomb structure for hood inner panel of a motor vehicle for pedestrian protection in accordance with the present invention.
Figure 2 shows the cross sectional views of honeycomb structure of the hood inner panel.
Figure 3 shows an arc made by the horizontal sides of Central ladder channels and one side of honeycombs as per the present invention.
DETAILED DESCRIPTION OF THE INVENTION:-
Pedestrian protection basically requires the following principals:
sufficient deformation space to absorb the kinetic energy of the pedestrian
head
construction of Vehicle structure softer at deformation zones necessary
deformation can occur to dissipate impact energy.
Hexagonal cut out 1 has a diameter of approximately 120mm, there are totally 10 complete equally sized hexagonal cut outs in the panel
- Central ladder cutout 2 has dimension of 215x107mm
- Central ladder cutout 3 has dimension of 160x115mm
- Central ladder cutout 4 has dimension of 272x73mm
Central ladder structure which has 3 horizontal ribs in the center, out of them 1 rib is merged with rear channel these ribs make an angle of 10 degree with one of the sides of hexagonal cutouts. The depth 13 in Fig A is 10mm. The cut outs are stretched hexagonal bigger then hexagonal cutouts, purposefully given to reduce weight at the center and same time depth of both the sides of ladder

channels (Fig B) is increased to 16mm. This concept helps in achieving uniform stiffness in the panel.
The channels of center ladder section shown in Fig B and Fig A, total depth 9 is 16mm, wall 5 is having 60 degree angle, wall 6 is having 50 degree angle with skin panel, width at the root 8 without radius is approximately 21mm and width at open end of the channel 14 is approximately 43mm. Width at the root 12 without radius is approximately 22mm and width at open end of the channel 7 is approximately 34mm. (The wall angle of channels in the panel may vary from 65 - 50 degrees, it can be 75 - 40 also)
The Honeycomb geometry at these area looks like incomplete which is purposefully done all over the profile to merge the honeycomb C-section to side section of the Hood, This kind of arrangement creates an predefined path for energy distribution. When head impact comes at any point of the hood the impact energy transmits uniformly in all the directions through honeycomb C Section and finally distributes equally to Hood side sections in the pattern as shown in image, which helps in absorbing the head impact force during pedestrian collision by reducing the peak.
The Honeycomb geometry at D, E ,and F area looks like incomplete which is purposefully done all over the profile to merge the honeycomb C-section to side section of the Hood, This kind of arrangement creates an predefined path for energy distribution. When head impact comes at any point of the hood the impact energy transmits uniformly in all the directions through honeycomb C Section and finally distributes equally to Hood side sections in the pattern as shown in image, which helps in absorbing the head impact force during pedestrian collision by reducing the peak.
Hexagonal cut out 1 whose one side is 10 degree from horizontal line, this is been done to meet torsional stiffness of hood. The horizontal sides of Central ladder channels and one side of honeycombs all together makes an arc as shown in the Figure 3, there is possibility of crumple if channels are in

horizontal axis, this structure helps in meeting durability as well as pedestrian safety.
Initially ladder structure was designed to minimize the weight at the centre. But CAE iterations revealed that because of weight reduction the stiffness failed at the center, so to maintain the same stiffness all over the panel, the present invention addresses the solution. The depth locally increased at ziz zag rib at the center ladder structure to gain the stiffness.
The main hurdle was Optimization between Durability and pedestrian safety. The hood inner panel should be stiff enough to pass durability and flexible enough to absorb head impact energy. This is totally a balanced process in which one cannot over design the hood for durability or pedestrian safety, too flimsy will lead to fail in durability and too stiff will lead to fail in pedestrian test. According to the latest iterations done on CAE -both durability and pedestrian tests we have achieved the target of passing all the DVP criterions and also Rated 5 STAR for EURO NCAP pedestrian safety legislation.
Maintaining clearance 75mm between hood and engine compartment parts was a big challenge. The section modulus was too tight, and there was a restriction of less space below the hood inner and had to work out the section modulus with this constraint to get a minimum space of 75mm. The present invention worked out with this limit and the purpose of pedestrian safety requirements and durability as well was solved.
The present invention provides following technical advantages
1. Uniform hood stiffness
2. Optimized draft angles to meet the safety, durability, NVH, customer sensitive (feel good) requirements.
3. Refined sections in order to reduce head deceleration and risk to death.

WE CLAIM:-
1. The ladder honeycomb hood structure for a motor vehicle for pedestrian protection comprising an inner panel having ten numbers of complete equally sized Hexagonal of equal diameter cut out with on side making 10° to the horizontal; a first Central ladder cutout formed with horizontal rib; a second Central ladder cutout formed with smaller length of horizontal rib than that of first ladder above the said first central ladder; a third Central ladder cutout formed below the said first central ladder with horizontal rib, merged with rear channel, having bigger length than that of the said first central ladder; the said hood structure an arrangement made in such a way that the said hexagonal cut outs equally formed on both side of said central ladder; and a number of unequal size hexagonal cut out formed in the space between said equal size hexagons and hood side section .
2. The ladder honeycomb hood structure as claimed in claim 1 wherein the diameter of the said equal size hexagonal cut out is diameter 120 mm.
3. The ladder honeycomb hood structure as claimed in claim 1 and 2 wherein the said first Central ladder cutout having dimension of 215x107mm, the said second Central ladder cutout having dimension of 160x115mm, and the said third Central ladder cutout having dimension of 272x73mm .
4. The ladder honey comb hood structure as claimed in claims 1 to 3 wherein the channels of center ladder section having total depth 16mm, the walls having 40 to 75 degree angle, with skin panel, the width at the root without radius is approximately 21mm and the width at open end of the channel approximately 43mm., and width at the root without radius approximately 22mm and width at open end of the channel s approximately 34mm.
5. The ladder honey comb hood structure as claimed in claim 4 wherein the said wall angle preferably 50 to 65 degrees.

6. The ladder honey comb hood structure as claimed in claims 1 to 5 wherein the said unequal size hexagonal cut out formed symmetrically at both side of central ladders.
7. The ladder honey comb hood structure as claimed in claims 1 to 6 wherein the depth locally increased at ziz zag rib at the center ladder structure to gain the stiffness.