OSNOVE: Kako Radi Motor?

[Black Knight]

Mislim da ovo svaki ozbiljan forum treba da ima...stoga...

Skoro sigurno ste u jednom trenutku pogledali pod haubu automobila i pomislili: šta je ovde motor i čemu sve ovo služi, ili ste čuli od nekoga da kaže "šesnaest ventilski motor", "dve bregaste" ili nešto slično i niste razumeli o čemu se tu tačno priča. Pokušaćemo da malo pojasnimo neke termine kao i da ukratko opišemo rad motora.



Kako radi motor?



Osnove

Svrha motora je da pretvara gorivo u kretanje i time obezbedi pokretanje automobila. Trenutno, najlakši način da se napravi kretanje od goriva je sagorevanje goriva unutar motora. Daklem, automobilski motor je motor sa unutrašnjim sagorevanjem - sagorevanje se odigrava u njegovoj unutrašnjosti. Treba zapaziti par stvari

- Postoje različite vrste motora sa unutrašnjim sagorevanjem. Dizel motori su jedna, mlazni motori druga, benzinski treća, a rotacioni (Vankel) opet neka četvrta grupa. Svaka od tih grupa naravno ima svoje prednosti i mane.

- Postoje i motori sa spoljašnjim sagorevanjem. Parna mašina je tipičan primer motora sa spoljašnjim sagorevanjem. Međutim zbog određenih razloga (velike dimenzije, mala efikasnost) ti motori su jako nepraktični za automobile.

Danas veliki procenat automobila koristi motor sa unutrašnjim sagorevanjem iz sledećih razloga:

1. Relativna efikasnost (u poređenju sa motorima sa spoljašnjim sagorevanjem)
2. Relativna jeftinost (u poređenju sa gasnim turbinskim motorima - koriste ih avioni)
3. Relativno lako dosipanje goriva (u odnosu na električne motore)

Ovo su prednosti tehnologije koja za sada omogućava najjeftiniju proizvodnju automobila.


Sagorevanje

Kada se kaže automobilski motor, uglavnom se misli na četvrototaktni ciklus sagorevanja koji obezbeđuje da se sagorevanje goriva pretvori u kretnju. Četvorotaktni ciklus je smislio Nikolaus Otto 1867. godine, pa je po njemu nazvan Otto ciklus. Ono što razlikuje benzinse i dizel motore je da smesu goriva i vazduha u cilindru koje je kompresovao klip kod benzinskog motora pali svećica iskrom, dok se kod dizela smeša sama pali usled visokog stepena kompresije koja usijava vazduh do tačke kada on sam eksplodira. Pojedinačno, radne faze četvorotaktnog obavljaju sledeće procese:
1. u****vanje
2. kompresovanje
3. ekspanizija
4. izduvavanje

Rekli smo da je za sagorevanje potrebno pomešati vazduh i gorivo. Za potpuno sagorevanje najpovoljniji odnos goriva i vazduha je stalan i iznosi (14,7 : 1 u korist vazduha kod benzinskih motora). Za povećanje dobijene energije (tako i snage motora) naprosto potrebno je sagoreti više smese. Zato motori veće zapremine po pravilu razvijaju veću snagu jer im u cilindar stane više smese. Klip (koji sabija smesu odn. vazduh) u radu se kreće između dva položaja - donje i gornje mrtve tačke pri čemu prelazi put koji nazivamo hod klipa. Uzmemo li u obzir njegov prečnik (klipovi su u pravilu okruglog preseka), zapreminu cilindra može se predstaviti kao prostor koji se nalazi između ta dva krajnja položaja klipa. Pri tome zapreminu nekog motora možemo predstaviti kao proizvod zapremine jednog cilindra i broja cilindara. Odnos najveće zapremine cilindra (kada je klip u donjoj mrtvoj tački) i prostora u koji je smesa sabijena dolaskom klipa u gornju mrtvu tačku nazivamo stepenom kompresije.

Od stepena kompresije znatno zavisi energija koju dobijamo sagorevanjem smese, a njegovim povećanjem (do izvesne granice) raste i snaga motora. Posledica sagorevanja smese je povećanje zapremine gasova unutar cilindra. Ova ekspanzija pokreće klip prema dole, a on posredstvom klipnjače okreće kolenasto vratilo (radilicu). Ovo pravolinisko kretanje klipa pretvara se u kružno koje se potom predaje prenosnom mehanizmu, a na kraju točkovima. Da bi motor mogao pravilno "disati", tj. u****vati smesu u cilindar i izbacivati iz njega produkte sagorevanja, brinu se ventili. Postoje dve vrste ventila: usisni i izduvni, a ritam njihovog otvaranja i zatvaranja diktira broj obrtaja motora koji se menja obzirom na to koliko je pritisnuta papučica gasa. Moderni motori radi bolje razmene gasova imaju više ventila po cilindru. Tako dva usisna i dva izduvna ventila jednom (četverocilindričnom) 16-ventilskom motoru omogućavaju znatno bolje "disanje", a time i ostvarivanje veće snage u poredjenju s klasičnom (dvoventilskom) verzijom.





(Taktovi su poređani s leva na desno)

1. takt: Usis (usisni ventil je otvoren, izduvni zatvoren)
2. takt: Kompresija (oba ventila su zatvorena, klip sabija smesu)
3. takt: Ekspanzija (iskra svečice pali smesu, a gasovi se šire potiskujući klip)
4. takt: Izduv (izduvni ventil je otvoren, usisni zatvoren)


Zapremina

Prostor u kome se komprimovanje i eksplozija smese dešavaju se pod kretnjom klipa menja, tj. menja svoju zapreminu. Ta zapremina, dakle, ima svoju minimalnu i maksimalnu vrednost. Razlika između njih se naziva zapreminom motora i meri se u litrama, kubnim centimetrima (ccm) ili u područjima gde još uvek ne važi metrički sistem u kubnim inčima (cin). Jedan litar ima 1000 ccm, dok jedan kubni inč ima oko 16,4 kubnih centimetara.

Na primer:
Motorna testera ima motor zapremine 40 ccm.
Motorcikl može imati motor od 50 pa do 1300ccm.
Sportski automobil može imati motor od 5l (ili 5000 ccm).
Većina običnih putničkih automobila danas ima između 1000 i 3000 ccm.


Cilindri imaju iste zapremine pa četvorocilindrični motor od 2.0l ima zapreminu jednog cilindra od 500ccm. U principu zapremina može ugruba da prikaže koliko motor može snage da razvije. Raspored cilindara u motoru može biti redni, u V (pod nekim uglom) ili položeni ili tzv. boxer motori.


Boxer motor ^.................................................. ........................................Redni motor ^



Motor u "V" rasporedu ^

[kilson]

[maki]

Dobro,samo nisu svi motori benzinci i cetvorotaktni
ima i dizela,i dvotaktnih.
Ajde rad dvotaktnog motora?
Sad da vas vidim

[Black Knight]

posto nisam bas na prijateljskoj osnovi sa "engineer" engleskim moze li bez prevoda? pa onda neko ovde da to lepo prevede strucno?
Evo za pocetak:

ovako izgleda dvotakti motor:


Ugradnja dvotaktnog motora ustvari je i najcesce rijesenje u ultralakom letenju. Vrlo povoljan odnos snage i tezine, vrlo jednostavan i bez suvisnih dijelova, ovdije ga je ucinio popularnom opcijom. Iako nekada vrlo uobicajena nestabilnost u radu dvotaktnih motora iz vremena prerada Trabanta, danas i nije primjerena modernijim dvotaktnim motorima i rijesenjima koja se sada primjenjuju. Iako njihova sama konstrukcija ne daje posebne novosti, mnogi od nas osvjedocili su se u njihovu trajnost.Na zalost otkazi dvotaktnih motora na zrakoplovima koji su se desavali, vrlo cesto su bili posljedica loseg ili gotovo nikakvog odrzavanja.

[Black Knight]

a ovako izgleda dvotaktni dizel motor:

[Black Knight]

a evo i dizel motora:

http://img85.exs.cx/my.php?loc=img85&image=diesel25kj.swf

za ovo vam je potreban flash player

http://fpdownload.macromedia.com/get/shockwave/flash/english/win95nt/7.0.19.0/flashplayer7installer.exe

p.s. sto ne moze da se okace flash animacije...?!

Edit 006

[Black Knight]

Ecu

mislim da ovo nebi trebalo da se prevodi pa stoga cu preneti text u potpunosti sa HSW.com


Sophisticated Engine Controls
Before emissions laws were enacted, it was possible to build a car engine without microprocessors. With the enactment of increasingly stricter emissions laws, sophisticated control schemes were needed to regulate the air/fuel mixture so that the catalytic converter could remove a lot of the pollution from the exhaust. (See How Catalytic Converters Work for more details.)


The computer from a Ford Ranger


Controlling the engine is the most processor-intensive job on your car, and the engine control unit (ECU) is the most powerful computer on most cars. The ECU uses closed-loop control, a control scheme that monitors outputs of a system to control the inputs to a system, managing the emissions and fuel economy of the engine (as well as a host of other parameters). Gathering data from dozens of different sensors, the ECU knows everything from the coolant temperature to the amount of oxygen in the exhaust. With this data, it performs millions of calculations each second, including looking up values in tables, calculating the results of long equations to decide on the best spark timing and determining how long the fuel injector is open. The ECU does all of this to ensure the lowest emissions and best mileage. See How Fuel Injection Systems Work for a lot more detail on what the ECU does.


The pins on this connecter interface with sensors and control devices all over the car.


A modern ECU might contain a 32-bit, 40-MHz processor. This may not sound fast compared to the 500- to 1,000-MHz processor you probably have in your PC, but remember that the processor in your car is running much more efficient code than the one in your PC. The code in an average ECU takes up less than 1 megabyte (MB) of memory. By comparison, you probably have at least 2 gigabytes (GB) of programs on your computer -- that's 2,000 times the amount in an ECU.


Each year, cars seem to get more and more complicated. Cars today might have as many as 50 microprocessors on them. Although these microprocessors make it more difficult for you to work on your own car, some of them actually make your car easier to service.

http://img84.exs.cx/my.php?loc=img84&im ... tro4xj.swf
Mouse over each item in the list of parts to view its location and description.

Some of the reasons for this increase in the number of microprocessors are:

The need for sophisticated engine controls to meet emissions and fuel-economy standards
Advanced diagnostics
Simplification of the manufacture and design of cars
Reduction of the amount of wiring in cars
New safety features
New comfort and convenience features

ECU Components
The processor is packaged in a module with hundreds of other components on a multi-layer circuit board. Some of the other components in the ECU that support the processor are:
Analog-to-digital converters - These devices read the outputs of some of the sensors in the car, such as the oxygen sensor. The output of an oxygen sensor is an analog voltage, usually between 0 and 1.1 volts (V). The processor only understands digital numbers, so the analog-to-digital converter changes this voltage into a 10-bit digital number.

High-level digital outputs - On many modern cars, the ECU fires the spark plugs, opens and closes the fuel injectors and turns the cooling fan on and off. All of these tasks require digital outputs. A digital output is either on or off -- there is no in-between. For instance, an output for controlling the cooling fan might provide 12 V and 0.5 amps to the fan relay when it is on, and 0 V when it is off. The digital output itself is like a relay. The tiny amount of power that the processor can output energizes the transistor in the digital output, allowing it to supply a much larger amount of power to the cooling fan relay, which in turn provides a still larger amount of power to the cooling fan.

Digital-to-analog converters - Sometimes the ECU has to provide an analog voltage output to drive some engine components. Since the processor on the ECU is a digital device, it needs a component that can convert the digital number into an analog voltage.

Signal conditioners - Sometimes the inputs or outputs need to be adjusted before they are read. For instance, the analog-to-digital converter that reads the voltage from the oxygen sensor might be set up to read a 0- to 5-V signal, but the oxygen sensor outputs a 0- to 1.1-V signal. A signal conditioner is a circuit that adjusts the level of the signals coming in or out. For instance, if we applied a signal conditioner that multiplied the voltage coming from the oxygen sensor by 4, we'd get a 0- to 4.4-V signal, which would allow the analog-to-digital converter to read the voltage more accurately (see How Analog and Digital Recording Works for more details).

Communication chips - These chips implement the various communications standards that are used on cars. There are several standards used, but the one that is starting to dominate in-car communications is called CAN (controller-area networking). This communication standard allows for communication speeds of up to 500 kilobits per second (Kbps). That's a lot faster than older standards. This speed is becoming necessary because some modules communicate data onto the bus hundreds of times per second. The CAN bus communicates using two wires.


Easier Design and Manufacturing
Having communication standards has made designing and building cars a little easier. A good example of this simplification is the car's instrument cluster.

The instrument cluster gathers and displays data from various parts of the vehicle. Most of this data is already used by other modules in the car. For instance, the ECU knows the coolant temperature and engine speed. The transmission controller knows the vehicle speed. The controller for the anti-lock braking system (ABS) knows if there is a problem with the ABS.

All of these modules simply send this data onto the communications bus. Several times a second, the ECU will send out a packet of information consisting of a header and the data. The header is just a number that identifies the packet as either a speed or a temperature reading, and the data is a number corresponding to that speed or temperature. The instrument panel contains another module that knows to look for certain packets -- whenever it sees one, it updates the appropriate gauge or indicator with the new value.

Most carmakers buy the instrument clusters fully assembled from a supplier, who designs them to the carmaker's specifications. This makes the job of designing the instrument panel a lot easier, both for the carmaker and the supplier.

It is easier for the carmaker to tell the supplier how each gauge will be driven. Instead of having to tell the supplier that a particular wire will provide the speed signal, and it will be a varying voltage between 0 and 5 V, and 1.1 V corresponds to 30 mph, the carmaker can just provide a list of the packets of data. Then, it is the carmaker's responsibility to make sure that the correct data is output onto the communications bus.

It is easier for the supplier to design the instrument panel because he doesn't need to know any details of how the speed signal is generated, or where it's coming from. Instead, the instrument panel simply monitors the communications bus and updates the gauges when it receives new data.

These types of communications standards make it very uncomplicated for carmakers to outsource the design and manufacture of components: The carmaker doesn't have to worry about the details of how each gauge or light is driven, and the supplier who makes the instrument panel doesn't have to worry about where the signals are coming from.



Smart Sensors
Clusters are now being used on a smaller scale for sensors. For instance, a traditional pressure sensor contains a device that outputs a varying voltage depending on the pressure applied to the device. Usually, the voltage output is not linear, depends on the temperature and is a low-level voltage that requires amplification.

Some sensor manufacturers are providing a smart sensor that is integrated with all the electronics, along with a microprocessor that enables it to read the voltage, calibrates it using temperature-compensation curves and digitally outputs the pressure onto the communications bus.

This saves the carmaker from having to know all the dirty details of the sensor, and saves processing power in the module, which otherwise would have to do these calculations. It makes the supplier, who is most up on the details of the sensor anyway, responsible for providing an accurate reading.

Another advantage of the smart sensor is that the digital signal traveling over the communications bus is less susceptible to electrical noise. An analog voltage traveling through a wire can pick up extra voltage when it passes certain electrical components, or even from overhead power lines.

Communication buses and microprocessors also help simplify the wiring through multiplexing. Let's take a closer look at how they do this.

Simplified Wiring
Multiplexing is a technique that can simplify the wiring in a car. In older cars, the wires from each switch run to the device they power. With more and more devices at the driver's command each year, multiplexing is necessary to keep the wiring from getting out of control. In a multiplexed system, a module containing at least one microprocessor consolidates inputs and outputs for an area of the car. For instance, cars that have lots of controls on the door may have a driver's-door module. Some cars have power-window, power-mirror, power-lock and even power-seat controls on the door. It would be impractical to run the thick bundle of wires that would come from a system like this out of the door. Instead, the driver's-door module monitors all of the switches.


Doors with lots of switches are becoming more and more common.


Here's how it works: If the driver presses his window switch, the door module closes a relay that provides power to the window motor. If the driver presses the switch to adjust the passenger-side mirror, the driver's door module sends a packet of data onto the communication bus of the car. This packet tells a different module to energize one of the power-mirror motors. In this way, most of the signals that leave the driver's door are consolidated onto the two wires that form the communication bus.

The development of new safety systems has also increased the number of microprocessors in cars.


Safety, Comfort and Convenience
Over the last decade, we've seen safety systems such as ABS and air bags become common on cars. Other safety features such as traction-control and stability-control systems are starting to become common as well. Each of these systems adds a new module to the car, and this module contains multiple microprocessors. In the future, there will be more and more of these modules all over the car as new safety systems are added.

Each of these safety systems requires more processing power, and is usually packaged in its own electronics module. But it doesn't end there. In coming years, we'll have all kinds of new convenience features in our cars, and each of these requires more electronics modules containing multiple microprocessors.

It seems that there is no limit to how much technology carmakers are going to pack into our cars. The addition of all these electronic features is one of the factors driving carmakers to increase the system voltage on cars from the current 14-V system to a 42-V system. This will help provide the extra power these modules require.

[Scorpio76]

Odličan thread, imam par pitanja pošto nisam neki poznavalac mehanike.
Prvo, šta je obrtni momenat (oznaka u Nm), čemu to služi i zašto dizel motori sa manjom snagom u kW imaju veći obrtni momenat.

Konkretno gledam nove motore za Ford Fieste i vidim benzince od 1,3 8V (50kW 106Nm) 1,4 16V (59kW 124Nm) i 1,6 16V (74kW 146Nm).
Dizel motor je 1.4TDCi (50kW 160Nm)

Da li neko zna koji je obrtni momenat od fieste 86.god 1,6 benz (71kW)

I naravno Srećna Nova Godina svima

Pozdrav

[BOOST]

Ja nas mislim da bi trebalo da se prevede

[maki]

I ja mislim da bi trebalo,iako solidno poznajem tehnicki engleski jer su mi sve "maintenance" knjige na engleskom sto se tice svih instrumenata na brodu opet se javljaju neki pojmovi koje nemogu sa sigurnoscu da razumijem

[kilson]

Ajd' kad svako misli, onda cu i ja neshto, poseban thread za Engine Management pa nadovezivanje sa softverskim/hardverskim tweak-om pomenutog?

[sw.brick]

Prvo, šta je obrtni momenat (oznaka u Nm), čemu to služi i zašto dizel motori sa manjom snagom u kW imaju veći obrtni momenat.

laicki jednostavnije za objasnjenje, obrtni momenat je snaga koja pokrece tockove i sto je broj veci znaci da je motor snazniji. uvek se daje za odredjeni konkretan broj obrtaja ili kao dijagram.
dizeli nisu manje vec kontra vece snage pazato po pravilu imaju bolje perfomanse od benzinaca pri identicnim obrtajima/ uslovima rada.

ta posledica nastaje kao rezultat vece kompresije dizela, jace eksplozije i time vece sile koja jace gura klip.

formalna statisticka snaga u KS ili kW pri maksimalnom broju obrtaja ne govori o sposobnosti motora da pokrece tockove i vise je marketinske svrhe/ papirnatog podatka.

mana dizela je da zbog vecih rotacionih masa mora sporije da se vrti od slicnog benzinca i time ne moze da dostigne broj obrtaja na max. uporediv sa benzincem.

sustinski i najlakse za razumeti- obrtni momenat je mogucnost sile da pokrece tockove i auto. jaca sila (Nm) bolje perfomanse.

ne zaboraviti da moze i manja sila ako je cesca primenjena (vise rpm) da omoguci bolje perfomanse.

recimo da sam se trudio da onako zargonski pojasnim.

[Guest]

@scorpio 76
brick ti je ovo dobro objasnio vezano za motor, posto sam ja shtreber ja cu ti malo objasniti fiziku
Vidi pocecemo od dimenzione formule za snagu jedinica je W odnosno kW
kada se W izvede od osnovnih jed. SI sistema dobija se
P=A/t
snaga=rad/vreme da se taj rad izvrshi
A=F x s
rad=sila x put

1wat=(1Njutn x 1metar) / 1 sekund
ovo je ono o cemu si ti pricao

Konkretno gledam nove motore za Ford Fieste i vidim benzince od 1,3 8V (50kW 106Nm) 1,4 16V (59kW 124Nm) i 1,6 16V (74kW 146Nm).
Dizel motor je 1.4TDCi (50kW 160Nm)

Njutn x metar ti je moment a deljenje sa sekundama su ti obrtaji.
Sad se pitas kako deljenje sa sekundama predstavlja obrtaje? . Pa lepo posto je sekund ispod razlomacke crte to ti je sekund na -1 stepen(matematika i fizika za 6. raz osnovne ) a sekund na -1 ti je Herc a velicina u Hercima ti je broj obrtaja u sekundi.Zato sto je Herc jedna puna oscilacija(perioda,obrtaj)-6000 ob/min= 100ob/sec=100Hz[herca]
obrtni moment ti je sila koja vlada na kraku(pogledaj prvu sliku) vidis da ob. moment zavisi od duzine kraka i sile koja deluje na kraju kraka a ta sila je tangenta na kruznicu, recimo da je kruznica tocak onda je tangenta sila koja se sa tockova prenosi na asfalt
vidi ovo
jugo 55 i golf I dizel
imaju istu snagu=40kW
ali vidi ovo
jugo se max vrti oko 6000 ob/min
golf se max vrti na 5000 ob/min
a snga je ista
posto su ob. moment i obrtaji motora obrnuto srazmerni znaci da golf ima veci obrtni moment ob. moment.
ovo ti je funkcija snage i ob. momenta za jedan zastavin motor

crvena je snaga a zuta ti je obrtni moment sa donje ose citas br. ob. motora sa leve citas snagu(ovo vazi za crvenu liniju) a sa desne citas ob. moment to ti je za zutu

[Black Knight]

dobro posto ja nisam ovoliko strucan (a i posle nove godine mi bas nesto ne ide razmisljanje) evo jedna kratka def. sa mehanickim pogledom na stvar...Pod dejstvom sile kruto telo se, u opstem slucaju, krece translatorno i rotira oko neke tacke.Obrtno dejstvo koje sila proizvodi odredjuje se velicinom koju nazivamo moment sile.
Moment sile je vektorska velicina i, kao takva, odredjena je svojim intezitetom pravcem i smerom.Tacku njenog dejstva nazivamo momentna tacka.

[Guest]

Bravo Ranko stvarno si paljevina Srpske potencije!!!
Ovo je bas dobra definicija, mislim da je otprilike tako i u knjizi.
Doduse ja sam malo pokusao to prakticno da docaram...
Nadam se da dam bio jasan
pozdrav!