19 Sistemul de Frinare

8/13/2019 19 Sistemul de Frinare

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2" Care este clasificarea mecanismului de acionare a fr!nei i cerinele fa% de construcia lor+

_________________________________________________________________________Fiabilitatea sistemului de acionare al frnelor joac un rol deosebit n asigurareafiabilitiinecesare pentru sistemul de frnare n ansamblu. Sarcinile cese impun sistemului deacionare sunt:-

transmiterea comenzii cu un randament ct mai ridicat, n oricecondiiimeteorologice i de eploatare!-

amplificarea suficient a efortului de comand, atunci cnd este cazul, fr a mri nmod anormal curseleelementelor de comand!-

simplitatea constructi".#n funcie de aceste cerine, alegerea judicioas a tipuluii structurii sistemului deacionare n raport cu tipul i dimensiunileautomobilului prezint o importan fundamentaldin punct de "edere aleficacitii frnei. $ractica mondial n construcia de automobile apermis o specializare

a tipurilor de acionri n funcie de tipul automobilului i de destinaiasistemului de frnare.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

$" Care este construcia i principiul de funcionare a mecanismului de acionare hidraulic+

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Sistemul de acionare hidraulic

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#n prezent, sistemul de acionare %idraulic se utilizeaz la o proporie co"ritoare dinparculmondial de automobile, aceasta din cauz c acest sistem de acionare are deformaiielasticemici i randament ridicat. &stfel, acestea ec%ipeaz totalitatea autoturismelor,autocamioanelor i autobuzelor de mic capacitate i o bun parte a autobuzelor iautocamioanelor de medie capacitate.

'a deza"antaje ale sistemului de acionare %idraulic pot fi amintite:

posibilitatea ieirii din uz a ntregii instalaii la deteriorarea etaneitilor ntr-un locoarecare!randamentul sczut la temperaturi joase sub()*' din cauza mririi "scozitiilic%idului de frn!fora de acionare a frnelor propriuzise limitat din cauza forei maime cu carepoate sacioneze conductorul auto +)... da/.Sistemul de acionare %idraulic a frnelor poate fi clasificat n urmtoarele trei categorii:sistem de acionare %idraulic cu un singur circuit!sistem de acionare %idraulic cu dou circuite!sistem deacionare %idraulic cu ser"omecanism.

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4" Care este construcia i principiul de funcionare a mecanismului de acionare pneumatic+

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__Sistemele de acionare %idraulice pre"zute cu ser"omecanism asigur ocreteresuplimentar a presiunii lic%idului de frn din conducte, atunci cndpresiunea realizabilnumai de fora aplicat de conductorul auto asupra pedalei deacionare a sistemului defrnare nu este suficient pentru frnarea roilor. #n acest scop se poate utiliza:energia%idraulic generat de o pomp antrenat de motorul automobilului, energiadepresiuniicreate n colectorul de admisie al motoarelor cu carburator sau o pomp de "acuum antrenat demotorul automobilului! energia aerului comprimat, debitat de un

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compresor antrenat demotorul automobilului. #n funcie de sursa de energieutilizat se definesc sisteme deser"ofrnare %idraulice, cu depresiune +"acuumatice/saupneumatice.

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)" Constructia i principiul de funcionare a amplificatorului hidrovacumatic a sistemului de fr!nare+

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*" Care este construcia i principiul de funcionare a compresorului+__________________________________________________________________________Dup% principiul de funcionare se distin/:6 compresoare volumice, care reali(ea(% comprimarea prinmicorarea unui volum de /a( !nchis !n spaiul de lucru al mainii.

6 compresoare dinamice, care reali(ea(% comprimarea !ntr-unproces cu cur/ere continu% a /a(ului, prin m%rirea ener/iei cinetice i,parial, i a ener/iei poteniale de presiune !ntr-un rotor cu palete, procesurmat de transformarea ener/iei cinetice !n ener/ie de presiune prin fr!nareacur/erii.6 compresoare cu 7et, care reali(ea(% comprimarea prinamestecarea curentului de fluid de 7oas% presiune cu un curent de !nalt%

presiune, re(ultatul fiind un curent de presiune medie"0'emple" Din prima /rup% fac parte compresoarele cu piston, din adoua - cele centrifu/e i cele a'iale, iar din ultima - e7ectoarele"

Compresoarele volumice reali(ea(% presiuni p!n% la #888 &ar, dauau de&ite relativ mici, su& )88 m$min" Compresoarele dinamice furni(ea(%

presiuni p!n% la 2) &ar la de&ite foarte mari" Compresoarele centrifu/ereali(ea(% de&ite de p!n% la 2)88 m$min, iar cele a'iale de&ite ce pot dep%i#8888 m$min"

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9" Care este construcia i principiul de funcionare a dispo(itivului de re/lare a fr!nei+____________________________________________________________________________In timpul franarii automobilul trage intr-o parte. Acest defect apare in general, datoritadereglarii franelor, precum si unor defectiuni ale sistemului de franare, cum ar fi:- existenta unor tamburi excentrice- montarea unor garnituri necorespunzatoare- folosirea unor arcuri de readucere a sabotilor prea tari- infundarea, deformarea sau fisurarea racordului flexibil- patrunderea unsorii la garniturile de frecare- spargerea membranei sau deteriorarea garniturii cilindrului de franare al unei roti- presiunea in anvelope diferita

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" De l%murit schema de lucru a sistemului de fr!nare la autocamionul GA;-**+________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________


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##" Construcia i principiul de funcionare a camerei de fr!nare la automo&ilul ;1>-#$#+________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

#2" Care este construcia i principiul de funcionare a fr!nei de staionare+________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

#$" Care este construcia i principiul de funcionare a amplificatorului vacumatic asistemului de fr!nare+

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#4" @ecanisme de fr!nare cu disc, construcia i principiul lor de funcionare+________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

#)" @ecanisme de fr!nare cu sa&oi, construcia i principiul lor de funcionare+________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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#*" Construcia i principiul de funcionare a cilindrului principal de fr!nare GA;-**+____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

#9" Care este destinaia i construcia AB-ului+___________________________________________________________________________________________________________________________________________________________________________________________________________________________

#" Care este rolul dispo(itivului electronic de diri7are a AB-ului+____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Bibliografie:#" Gh"ratila, @ariana ratila, t"amoila Automo&ile, cunoatere, !ntreinere i

reparaie" 0ditura didactic% si peda/o/ic%, ="A" Bucureti #


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19 Sistemul de Frinare

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