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V diplomskem delu je predstavljena obdelava treh načinov sprostitev za centriranje membrane pred vtiskovanjem na grelcu čepne svečke. Cilj naloge je izdelati in optimizirati sprostitev, ki bo med vtiskovanjem membran proizvajala najmanj izmetnih kosov, prav tako pa mora biti oblika zanesljivo merljiva na obstoječi merilni opremi v podjetju, saj lahko le tako zagotovimo, da so kosi, pred nadaljnjo montažo, pravilnih dimenzij. V nalogi so predstavljeni rezultati vtiskovanja membran ter težave, ki se pojavijo pri določenih oblikah sprostitve. Ugotovljeno je bilo, da nam konična oblika sprostitve, ki jo stružimo vzvratno, poda najboljše rezultate z vidika sil vtiskovanja membran in zmanjšanja izmeta. Bachelor thesis presents processing of three types of releases used for centering the membrane before stamping on the heater of glow plug. Aim is to make and optimize the type of a release, which will represent the least scrap parts during stamping of membranes. Shape must be reliably measurable with the existing equipment, as it is the only way to ensure that the pieces are of correct dimensions before further assembly. Thesis includes the results of stamping of membranes, and problems that occur with certain type of release. We found out that the conical shape of the release, which is machined backwards, gives us the best results in terms of forces during stamping, consequently reducing number of bad parts.

Zlitine FeCrAl (Kanthal ®) so visokotemperaturno obstojne zlitine železa, kroma in aluminija, z odlično oksidacijsko odpornostjo pri povišanih temperaturah. V večini primerov se uporabljajo za električne grelne in konstrukcijske elemente, obstojne pri povišanih temperaturah (do 1400 °C). Oksidacijska odpornost teh zlitin je posledica nastanka termodinamično stabilnega in za kisik nepropustnega aluminijevega oksida (Al2O3) na površini, ki jih ščiti pred nadaljnjo oksidacijo. Kljub odlični oksidacijski odpornosti, pa je lahko življenjska doba elementov izdelanih iz teh zlitin omejena, če so pogosto izpostavljeni termičnemu cikliranju pri temperaturah nad 1000 °C. Razlog za to je pokanje oksidne plasti, zaradi hitrih temperaturnih sprememb in različnih raztezkov oksidne plasti ter kovinske osnove ter nadaljnja oksidacija aluminija, zaradi konstantne tvorbe nove oksidacijske plasti. Vse dokler je v podpovršinski plasti zlitine dovolj velika koncentracija aluminija, bo razpoko hitro zapolnila nova plast aluminijevega oksida. Ko pa se enkrat aluminij v podpovršinski plasti porabi in se njegova koncentracija zniža pod kritično vrednost (< 3 mas.%), zaščitna plast aluminijevega oksida ne bo več nastala, kar vodi do oksidacije železa in ostalih legirnih elementov in s tem postopnega propada grelnega oz. konstrukcijskega elementa. Namen magistrskega dela je bil povečanje koncentracije aluminija v površinski plasti FeCrAl zlitine (® Kanthal AF) s čemer bi se podaljšala sposobnost obnavljanja oksidne plasti in posledično življenjska doba elementov izdelanih iz te zlitine. Z namenom povečanja koncentracije aluminija v podpovršinski plasti smo zlitino obdelali s postopkoma aluminiziranja v zasipu. Postopek aluminiziranja je potekal v cevni peči, v kateri smo žarili vzorce zakopane v mešanici prahov sestave 1 mas.% Al, 1 mas.% NH4Cl in 98 mas.% Al2O3 pri različnih časih in temperaturah. Po aluminiziranju je sledila visokotemperaturna oksidacija aluminiziranih ter za primerjavo tudi nealuminiziranih vzorcev. Oksidacija je potekala pri 1200 °C v zračni atmosferi. Aluminizirane in oksidirane vzorce smo analizirali z vrstičnim elektronskim mikroskopom (SEM). Preiskovali smo stanje površine, globino aluminiziranja in strukturo oksidnega površinskega sloja. Ugotavljamo, da so temperatura in čas žarjenja ter sestava zasipa ključnega pomena do katere globine bo difundiral aluminij v osnovni material med procesom aluminiziranja v zasipu in katere faze se bodo tvorile na površini. Naloga je potekala v okviru projekta za podaljšanje življenjske dobe žarilnih svečk dizelskih motorjev. FeCrAl (Kanthal ®) alloys are high-temperature resistant alloys of iron, chromium, and aluminum, with excellent oxidation resistance at elevated temperatures. In most cases are used for electrical heating and structural elements resistant to elevated temperatures (up to 1400 °C). The oxidation resistance of these alloys is related to the formation of thermodynamically stable and oxygen-impermeable alumina (Al2O3) on the surface, which inhibits further oxidation of the material. Despite their excellent oxidation resistance, the life span of the elements made of these alloys is limited if they are subjected to thermal cycling at temperatures above 1000 °C. The reason for this is cracking of the alumina scale, due to different temperature expansion compared to the alloy matrix, and the consumption of the aluminium in the subsurface area of alloy matrix, due to the constant re-formation of the alumina scale. Once the aluminium content in the subsurface area is reduced beneath critical concentration (

Cilj magistrskega dela je razvoj, testiranje in izdelava stikalnega napajalnika za ogrevalne svečke dizelskih motorjev. Napajalnik uporablja vir električne napetosti v vozilu in skrbi za pravilno napajanje štirih ogrevalnih svečk za dizelske motorje Hidria PSG, ki so nameščene v blok motorja. Svečke napaja na ukaz računalnika v vozilu in mu pošilja povratne informacije o stanju napajanja. Najprej smo preučili zgradbo in delovanje ogrevalne svečke za dizelske motorje s senzorjem tlaka Hidria PSG. Z dobljenimi rezultati in z upoštevanjem želja naročnika je bil izdelan seznam načrtovalskih zahtev za namenski stikalni napajalnik. Napajalnik mora delovati pri vhodnih napetostih med 16 V in 32 V. Vsak izmed dveh izhodov napaja dve ogrevalni svečki Hidria PSG s konstantno izhodno napetostjo 4,4 V in največjim tokom 15 A. Izhodi napajalnika so aktivni samo kadar je na priključku ST pravokotni signal s frekvenco 32 Hz med 0 V in 7 V ter 50 % delovnim ciklom, ki ga ustvari računalnik v vozilu. Če se oba izhoda nahajata v 10 % območju nastavljene izhodne napetosti, je signal diagnostike v visokem stanju. V primeru prevelikega toka na katerem izmed izhodov, krmilnik izhod izklopi. Drugi izhod v takem primeru ostane aktiven, diagnostika na nizkem potencialu. Ohišje in razpoložljivi priključki napajalnika so že vnaprej določeni. Preiskani so bili namenski krmilniki na tržišču. Uporabljen je bil krmilnik MAX17559 s tokovnim načinom krmiljenja, ker je bilo ocenjeno, da je najbolj primeren za takšen idelek. V programu Altium Designer je bila načrtovana shema upoštevajoč načrtovalske zahteve, v programu EE - Sim SE je bila izvedena simulacija delovanja. Izbrane so bile vse potrebne komponente za sestavo napajalnika. Izdelano je bilo tiskano vezje, ki smo ga vstavili v ohišje. Testirano je bilo delovanje napajalnika in dodatnih funkcij, opravljene so bile tudi meritve sevalnih emisij. Rezultat je razvit in izdelan A vzorec stikalnega napajalnika za ogrevalne svečke dizelskih motorjev Hidria PSG, ki je bil poslan kupcu v potrditev funkcionalnosti izdelka. Purpose of this master’s thesis is a development, testing and production of a switch-mode power supply for the diesel engine glow plugs. The device uses source of the electrical power in the vehicle and correctly supplies the energy to the four glow plugs for diesel engines Hidria PSG, located in the motor block. Computer in the vehicle gives the signal when the supply of the glow plugs is needed, device gives a feedback to the computer about the supply status. At first, construction and operational characteristics of glow plug for diesel engines with pressure sensor Hidria PSG were investigated. Using the results and considering the customer’s wishes, a list of design requirements for switch-mode power supply was made. The power supply has to operate at input voltages from 16 V to 32 V. Each of the two outputs powers two glow plugs Hidria PSG with a constant voltage of 4,4 V and maximum current of 15 A. Outputs are active only when a 32 Hz square signal with 7 V amplitude and 50 % duty cycle is generated by the computer in the vehicle, connected to the ST connector. Diagnostics signal is high if both output voltages are in 10 % range of the pre-set voltage. If an overcurrent is detected, controller switches the output off. In this case the second output is still active, diagnostic signal is low. Housing of the product and the connectors were defined before. After the research of available controllers, decision to use MAX17559 with current mode control was made because it was recognized as the most suitable for this product. Having in mind the design requirements the schematics in Altium Designer and behaviour simulation in EE – Sim SE simulator was done. All the components needed for the switch-mode power supply were chosen. Printed circuit board was made and housed. Behaviour, additional functions and radiated emissions of power supply were tested. The result is developed and produced A prototype of switch-mode power supply for the diesel engine glow plugs Hidria PSG, which was sent to the buyer to confirm the functionality of the product.

Glow plugs are currently the most employed solution to promote ignition in light-duty diesel engines during low temperature cold start. Improved knowledge about the mechanisms that control ignition and flame development under such conditions is necessary for design purposes, especially with current trends to reduce engine compression ratio. This paper aims to analyze the influence of the glow plug configuration (location and temperature) on cold start combustion. Experimental tests carried out in an optical engine with high speed visualization have confirmed that spray-glow plug configuration influences the whole combustion process through pilot ignition. Ignition of pilot injection is controlled by glow plug to spray distance, by glow plug temperature and by fuel and air motion after the end of injection. Nevertheless, glow plug temperature effect starts to be negligible above a certain value, since chemical ignition delay cannot be further reduced. © 2011 Elsevier Ltd.