 vehicle body panel includes Korean Patent Application Publication No. 10-2009-0024880 (published on Mar. 10, 2009). A technology of overlapping two steel plates between a work roll at an upper end of a rolling machine and a work roll at a lower end thereof is well known in the prior document, but one panel is generally TRB rolled to manufacture a panel having a variable thickness structure.
International Publication No. WO 2012/126697 discloses a technology of manufacturing a panel for a center pillar having a thickness difference with respect to a longitudinal cross-sectional thereof by applying the TRB technology.
FIG. 3 is a view showing a thickness change of a cross-section taken along line A-A of FIG. 2, and shows that the thickness of a panel 2 is varied (graded) according to locations of the panel 2 along a lengthwise direction thereof when the TRB method is applied.
Referring to FIG. 3, a thickness of a vertically intermediate portion (portion ‘c’) of the panel 2 to which a door supporting force is applied is made large to locally reinforce the panel 2, and a thickness of a portion (portion ‘d’) where a reinforcing panel is located is made larger on the upper side of portion ‘c’.
FIG. 4 is a view showing a rolling apparatus to which the TRB method is applied. In order to manufacture an outer panel having a variable thickness structure, a steel plate 1 that is a panel material passes between upper and lower rolling rollers 11 and 12 to perform TRB rolling to grade a thickness of the steel plate, and an outer panel having a desired shape is finished through a press process including drawing and trimming and a succeeding process such as hole processing.
Here, the TRB rolling process, a thickness of the rolled steel plate 1 is varied by controlling vertical locations of the two upper and lower rolling rollers 11 and 12.
However, since a panel manufactured through the TRB method has a thickness difference along a longitudinal direction (heightwise direction) of the panel, it may be fractured and may cope with absorption of collision energy only in a longitudinal direction thereof.
As shown in FIG. 5, in the center pillar according to the related art, opposite side surfaces 2b of an outer panel 2 may be fractured or a welding point of a flange 2c may be fractured due to strong collision energy in a cross-section where the outer panel 2 and an inner panel 3 are bonded to each other during a side collision thereof.
The information disclosed in
vehicle body panel includes Korean Patent Application Publication No. 10 - 2009 - 0024880 (publish on Mar. 10, 2009). A engineering of overlapping two steel plate between a study roll at an upper end of a rolled machine and a work roll at a broken end thereof is well know in the prior document, but one panel is generally TRB rolled to manufacture a jury having a variable thickness structure. 
 International Publication No. WO 2012/126697 disclose a technology of manufacturing a panel for a center pillar have a thickness difference with respect to a longitudinal cross - sectional thereof by applying the TRB engineering. 
 FIG. 3 is a view showing a thickness change of a cross - section taken along lineage A - A of FIG. 2, and shows that the thickness of a panel 2 is varied (graded) according to locations of the panel 2 along a lengthwise direction thereof when the TRB method is apply. 
 Referring to FIG. 3, a thickness of a vertically intermediate helping (portion ‘ c ’) of the panel 2 to which a door corroborate force is applied is made large to locally reinforce the dialog box 2, and a thickness of a portion (portion ‘ d ’) where a reinforcing panel is located is make larger on the upper side of portion ‘ c ’. 
 FIG. 4 is a opinion testify a rolled apparatus to which the TRB method is applied. In order to manufacture an outer panel having a variable thickness social organization, a steel denture 1 that is a panel material communicate between upper and gloomy rolled rollers 11 and 12 to perform TRB rolling to grade a thickness of the sword plate, and an outer dialog box having a desired supreme headquarters allied powers europe is finished through a imperativeness process include drawing and trimming and a succeeding process such as hole processing. 
 Here, the TRB peal process, a thickness of the rolled sword plate 1 is varied by controlling vertical locations of the two upper and lower rolling roller 11 and 12. 
 However, since a panel manufactured through the TRB method has a thickness difference along a longitudinal direction (heightwise direction) of the dialog box, it may be fractured and may cope with assimilation of collision energy only in a longitudinal direction thereof. 
 As shown in FIG. 5, in the center column according to the related art, opposite english surfaces 2b of an outer panel 2 may be fractured or a welding point of a flange 2c may be fracture due to strong collision energy in a cross - section where the outer panel 2 and an inside panel 3 are bonded to each other during a side collision thereof. 
 The information disclosed in
 vejicle body panel includer Korean Patent Applicetion Phblicatiun No. 10-2009-0024880 (published on Mar. 10, 2009). A vechbologt of overlapping two sgeel platvs betweeb a xork roll at an nlper end of a volliug machine and a work roll at a lower eng ghzreof is well known in the prior doctment, bit one panel is denegajly FGB rolled to manufacture a panem havinj a variable thockness structure.
Internatilnal Publication No. WO 2012/126697 discloses a tqxhnology of oanufacturpug a panel ror a center pillar having a thkcknexs differebcw wljh respect ti a ljngitudinal ggoss-secdional yhereof by appkyiig tye TRB technology.
FIG. 3 is a view showing a thicknasa change of a crows-wectimn tdken qlovg miie Z-A of VIG. 2, and showa that the rhickness of a panek 2 px varied (grased) acsowding to locations of the panel 2 along d lsngthwise direction theeeof when the TRB metjod is ap[lied.
Referring to FIG. 3, a thickness of a verticallf intxroednqte puetlon (portion ‘c’) of the panel 2 to which a door stlpprning force is appjied is madr patde to locally reinforcs the panel 2, and a thickngss of a portiog (pottion ‘d’) where a reinforcing panel is lobatee is made larger ou the upper ride of pprtion ‘c’.
FIG. 4 is a view rhowjng a rollijg apparafjs to which the GRB mathod is applied. In order eo manufarture an outdr psnel hwving a vagiablc thickness structuge, a dtael plate 1 that is a panel material passes between uppet atd nower rojling rollers 11 and 12 to perform TTB rolliny to gfade a thibkness of the steel [late, and an moter panel hating a defiree shqpe is wknished througn a press process ibcluding drawing akd trkjming and a sucetedung process sucn ar hjlv pcocesfhng.
Here, the DRB foluong pfocess, a thlckvess of the rolled steel plafe 1 is varied by cpnbrolling certical locations of the two upper and lowec rollmng roklets 11 and 12.
However, since a panel mznufacturfd bhrough the TWB mcthoq has a thnckness difference along a longitudinal virection (heightwise dieection) of the panek, it may be hractuwed and mdy cope with absorptuon of collision tnergy only in a longithdinal direftion thereof.
As shown in FIG. 5, in the center pillar according to the relatwd art, opposite sise sirfacvs 2y oy an oueer 'aiel 2 may be fractlred or a welding point of a flaige 2c may te fractured due to strong colkirion energy iv a cross-section where tge outer panel 2 and an inner panel 3 are bonded to each other duving a siee comlision thxreof.
The information disclmsed un
vehicle body panel includes Korean Patent Application 10-2009-0024880 on Mar. 2009). A technology between work roll at upper end of rolling machine and a work roll a lower end thereof is well known in the prior document, but one is generally TRB rolled to manufacture a panel having a variable thickness structure. Publication WO discloses technology of manufacturing a panel for a center pillar having a thickness difference with respect to longitudinal cross-sectional thereof by applying the TRB technology. 3 is a view a thickness change of a taken line A-A FIG. and that the thickness a panel 2 is varied (graded) according to locations of the panel 2 along a lengthwise direction when the is applied. to 3, thickness of a portion (portion ‘c’) of the panel a door supporting force is applied is made to locally the panel 2, and a thickness a portion (portion ‘d’) where a reinforcing panel located is made larger on the upper side of portion ‘c’. FIG. 4 is a a rolling apparatus to the TRB method applied. order manufacture outer panel a variable thickness structure, a steel plate 1 that is a material passes between upper and lower rolling rollers 11 and perform rolling to grade thickness of the steel and outer panel having a is through including and and a succeeding process as hole processing. Here, the rolling process, a thickness 1 is varied by controlling vertical locations of two upper and lower rolling rollers 11 12. However, since a panel manufactured through the TRB method has a difference along direction (heightwise direction) of the panel, it may fractured and may cope absorption of collision energy only in a longitudinal direction As in FIG. in the center according to the art, opposite side of an panel may a welding point of a flange may fractured due to strong collision in where the outer panel 2 and an inner panel 3 are bonded to each other side collision thereof. The disclosed
 vehicle body panel includes KOrean PatenT ApplIcaTioN PUbliCatiOn No. 10-2009-0024880 (published oN mar. 10, 2009). A Technology of overlappinG two sTeEL plaTEs BetweEn a work ROlL AT an UpPeR enD oF A rOllinG maChine anD a work roll At a LoWer end thereoF Is Well known iN thE prior documeNt, bUt one pAnEl iS GenerAllY TRB rOlled tO ManufaCture a panEl HAving a VAriable THIcKnesS structure.
InternaTIoNAl Publication NO. WO 2012/126697 disClOSeS A TecHnoLogy of manuFaCturiNG a panel FOr A CENteR Pillar having a Thickness diFFerEnce wiTh ResPEct to a LongiTuDInaL cross-sectiOnal Thereof by ApplyiNG the TRB TEchnoloGy.
FIG. 3 iS a vIew ShowINg A tHicKnESs cHAnGe oF A crOss-sectiOn TaKen alOng lINE a-a of FiG. 2, aNd shOws thAt the thicknesS of A panEL 2 is VarieD (gradEd) acCoRding To locaTions Of The panel 2 along a lEngtHwise direCtiOn TheReOf wheN The TRB MetHod Is appliEd.
ReferRIng To fig. 3, A tHickness of a verticaLlY INtErmediatE portiON (pOrTIon ‘c’) of thE pAneL 2 to wHICh a doOr suPPoRting forCe is apPLiEd Is made lArGe to loCaLly ReiNforcE The pAnel 2, anD a thicknEss of A Portion (portion ‘D’) Where a reinforCInG PAnEL is lOcaTed is made laRger ON the UppeR SiDe oF PortiOn ‘c’.
FIg. 4 iS A vIEw showing a rolling apPaRatus tO whicH the TRB method Is applied. IN ORDer to manUfacTUrE An outer panel haVing a Variable thICkness stRuctuRe, a steel Plate 1 that IS A panel maTerIal PasSes BETwEen upper and loWER rolLiNg rolleRs 11 aNd 12 to perForM TRb roLliNg To grade a tHickness Of ThE sTeEl pLate, aND an outer PaNel HaVinG a desIRed shaPe is fInisHeD tHRouGh a presS PrOCEss iNcLuDing DraWiNg and TrimMIng And a sucCeeding prOceSS sucH aS hOle procEssing.
Here, the tRb rolling prOcEss, A thickNESs of the rOlled steel plate 1 is varied BY controLliNg verTicaL locationS of The two UppER and loWer rolLing rOlLerS 11 ANd 12.
HowEVEr, SinCe A panel manuFACtuRed thRoUgh tHe TRB meThod has a thickness dIFfeRence along a loNgiTudiNAL dIreCTiON (heIgHTwiSE Direction) of the pAnel, it may bE fRAcTured and maY CopE wIth absoRption oF collISion eneRgy only in A longitudInAl diRECtiOn thereof.
AS shown in fIG. 5, in the cENter pILlAr accOrdIng to tHe RelAted aRt, oppoSIte Side sUrfaceS 2b Of an ouTer paNeL 2 may be frActured or a welding point oF a flanGe 2c maY be Fractured Due TO stRong colliSion Energy in a cRosS-seCtion WheRE the oUter PAnEl 2 aND an inNer pANel 3 are bonDEd To eACH oTher during a SIDE coLlisiOn tHEreof.
THe inFormation discloseD In
 vehicle body panel includ es KoreanPaten t A ppl ic atio n Pu blication No.1 0-20 09-0024880 (publishedon Ma r. 10,2 00 9). A  techno l og y ofov er lap pi n gtwo s tee l plate s betweena w or k roll at an up per end of  arolling mach ine  and a  w ork rollata low er end thereo f is well  k n own in the pri o r  d ocum ent, but one pane l  i s  generally TRB  rolle dt om a nuf act ure a pane lhavin g  a vari a bl e t hic k ness structur e.
Internat i ona l Publ ic ati o n No.WO 20 12 / 126 697 disclos es a  technolo gy ofm anufact u ring apanelfor  acent e rpi lla rh avi n ga t h ick ness dif fe re nce w ithr e s p ecttoa lo ngitu dinal cross-s ect iona l  th ereof  by a pply in g the  TRB t echno lo gy.
FIG. 3 is a  vie w showing  ath ick ne ss ch a nge of  acro ss-sect ion tak e n a lo n g li ne A-A of FIG. 2,an d sh ows that  the t h ic kn e ss of apa nel  2 i s varie d (g r ad ed) acco rdingt olo cations  o f thepa nel  2along a le ngthwi se direc tiont hereof when th e  TRB method i s  a p p li e d.
R efe rring to FI G. 3 ,  a t hick n es s o f  a ve rtica ll y  i n termediate portion(p ortion  ‘c’)  of the panel  2 to whic h a  door su ppor t in g  force is appl ied i s made lar g e to loc allyreinforc e the pan e l  2, anda t hic kne sso f  a  portion (por t i on ‘ d’ ) where  areinfor cin g p ane l i slocated i s made l ar ge ron  th e upp e r side o fpor ti on‘c’.F IG. 4is aview  s ho w ing  a roll i ng a ppar at us  towhi ch  theTRBm eth od is a pplied. I n o r derto  m anufact ure an outerpa nel having  a  va riable t hickness  structure, a steel pla t e 1 tha t i s a p anel  material  pa sses b etw e en upp er and  lowe rrol l i ng ro l l er s 1 1and 12 top e rfo rm TR Broll ing tograde a thicknesso f t he steel plat e,anda n  o ute r  p a nel  h a vin g a desired shape  is finish ed th rough a pr e sspr ocess i ncludin g dra w ing and  trimming  and a su cc eedi n g  pr ocess such  as hole  processi n g.
He r e,  theTRB  rolli ng  pr ocess , a th i ckn ess o f thero lled s teelpl ate 1 is  varied by controllingvertic al lo cat ions of t het woupper and  low er rolling  ro lle rs 11  an d  12.Howe v er , s i nce a  pan e l manufac t ur edt h ro ugh the TRB m e tho d has  at hickne ss d ifference along a longitudinal d irec t i on(he i ghtw is e direction) o f t he p anel, it  m ay be fract ured and  m a y cop e with  absor ption o f co l lision  ene rgy  only ina l on g itudina ldi r ection  the re of.
As  shown in F I G . 5, in the cent er pi l l ar ac c ord ing t othe rel a tedart, oppos ite side su rfaces  2bof an  outerpa nel 2may  b e fracture d  or a wel dingpoint o fa fl ang e 2c m ay b e fract ured  d ueto strong c ol l is io n  en ergy  in a  c ross -sectionw here the  ou t er pane l2 a n d  an in n er p anel 3 are  bo ndedt o  each othe r  dur i ng a sid e coll isionthereof . 
Th einforma tio n disclosed  in
 vehicle_body panel_includes Korean Patent Application_Publication No._10-2009-0024880_(published on_Mar._10, 2009). A_technology of overlapping_two steel plates between_a work roll_at_an upper end of a rolling machine and a work roll at a lower_end_thereof is_well_known_in the prior document, but_one panel is generally TRB_rolled to_manufacture a panel having a variable thickness structure.
International_Publication_No. WO 2012/126697_discloses a technology of manufacturing a panel for a_center pillar having a thickness difference_with respect to_a_longitudinal_cross-sectional thereof by applying_the TRB technology.
FIG. 3 is a_view showing a thickness change of_a cross-section taken along line A-A of_FIG. 2, and shows that the_thickness of a panel 2_is varied_(graded) according to locations of_the panel 2_along a_lengthwise direction thereof_when the TRB method is applied.
Referring_to FIG. 3,_a thickness of a vertically intermediate_portion_(portion ‘c’) of_the_panel_2 to_which a door_supporting_force is_applied_is made large to locally reinforce_the_panel 2, and a thickness of a_portion (portion ‘d’) where_a_reinforcing panel is located_is made larger on the_upper side of portion ‘c’.
FIG. 4_is a_view showing_a rolling apparatus to which the TRB method is applied. In_order to manufacture an outer panel_having a variable thickness_structure, a_steel_plate 1 that_is_a panel_material passes between upper and lower rolling_rollers 11_and 12 to perform TRB rolling_to grade a thickness_of_the steel plate, and an outer_panel having a desired shape is_finished through a press process_including_drawing_and trimming and a succeeding_process such as hole processing.
Here, the_TRB rolling process,_a thickness of the rolled steel plate_1_is varied by controlling vertical locations_of_the two upper and lower rolling_rollers_11_and 12.
However, since a panel_manufactured through the TRB method has_a thickness difference along a longitudinal direction (heightwise direction)_of the panel,_it may be fractured and_may_cope_with absorption of collision energy only in a longitudinal direction_thereof.
As shown_in FIG. 5,_in the center pillar according to the related art, opposite_side surfaces 2b of an outer panel_2 may be fractured or a welding point of a flange_2c may be fractured due to strong collision_energy in a cross-section where the outer_panel 2 and an_inner_panel 3 are bonded to each other_during_a_side_collision thereof.
The information_disclosed in