Overhead camshaft engine sahifasining manbasini koʻrish

[[Fayl:Head_D15A3.JPG|thumb|OHC silindrli kallagi (1987-yil Honda D15A3 dvigateli uchun)]]
'''Yuqori gaz taqsimlash vali''' ('''OHC''') '''dvigateli''', '''gaz taqsimlash vali ''' – yonish kamerasi ustidagi silindr boshida joylashgan pistonli vosita<ref name="Hillier"/><ref name="Stoakes">{{Kitob manbasi|last=Stoakes|first=Graham|title=Principles of Light Vehicle maintenance & repair|url=https://archive.org/details/isbn_9780435048167|series=Heinmann Work-Based Learning|year=2011|publisher=Babcock International Group and Graham Stoakes|isbn=9780435048167|pages=[https://archive.org/details/isbn_9780435048167/page/208 208]–209|chapter=3}}</ref>. Bu gaz taqsimlash vali dvigeatel blokidagi yonish kamerasi ostida joylashgan oldingi yuqori klapanli dvigatellardan (OHV) farq qiladi<ref>{{Yangiliklar manbasi |title=OHV, OHC, SOHC and DOHC (twin cam) engine - Automotive illustrated glossary |language=inglizcha |work=www.samarins.com |url=https://www.samarins.com/glossary/dohc.html |access-date=20-sentabr 2018-yil}}</ref>.

''Yagona gaz taqsimlash vali'' (SOHC) dvigatellari silindrlar qatoriga bitta gaz taqsimlash valiga ega. ''Ikki gaz taqsimlash vali'' (DOHC, shuningdek, „egizak kamera“ sifatida ham tanilgan<ref>[[Harley-Davidson Twin Cam engine]], [[Fiat Twin Cam engine]], [[Alfa Romeo Twin Cam engine]], [[Quad 4 engine]], [[Lotus-Ford Twin Cam]]</ref>.) dvigatellarda har bir bankda ikkita gaz taqsimlash vali. DOHC dvigatelidan foydalanadigan birinchi avtomobil 1910-yilda ishlab chiqarilgan. 1940-yillardan boshlab DOHC dvigatellaridan foydalanish asta-sekin oʻsib bordi, bu esa 2000-yillarning boshlarida DOHC dvigatellaridan foydalangan holda koʻplab avtomobillarning paydo boʻlishiga sabab boʻldi.

== Dizayni ==
OHC dvigatelida gaz taqsimlash vali dvigatelning yuqori qismida, yonish kamerasining tepasida joylashgan. Bu gaz taqsimlash vali dvigatel blokida joylashgan oldingi yuqori klapanli dvigatel (OHV) va tekis dvigatel konfiguratsiyasidan farq qiladi. OHC va OHV dvigatellaridagi klapanlar yonish kamerasining tepasida joylashgan, ammo OHV dvigateli harakatni gaz taqsimlash validan klapanlarga oʻtkazish uchun surish tirgaklari va qoʻltiqli qoʻllarni talab qiladi, OHC dvigatelida esa toʻgʻridan-toʻgʻri gaz taqsimlash vali tomonidan boshqariladigan klapanlar mavjud.

Bir xil miqdordagi klapanli OHV dvigatellari bilan taqqoslaganda, OHC dvigatelida pistonli komponentlar kamroq va klapanlar inertsiyasi kamroq. OHC dvigatellaridagi bu kamaytirilgan inertsiya yuqori dvigatel tezligida (RPM) kamroq valf floatiga olib keladi<ref name="Hillier"/>. Salbiy tomoni shundaki, gaz taqsimlash vali boshqarish uchun ishlatiladigan tizim (odatda zamonaviy dvigatellarda tasmali uzatma) OHC dvigatelida murakkabroq. OHC dvigatellarining kamchiliklari shundan iboratki, silindr boshini olib tashlashni talab qiladigan dvigatelni taʼmirlash vaqtida gaz taqsimlash vali dvigatel vaqtini qayta oʻrnatish kerak.

OHC dvigatellarining yana bir asosiy afzalligi shundaki, qabul qilish va chiqarish portlarining oʻlchami, joylashuvi va shaklini optimallashtirish uchun koʻproq moslashuvchanlik mavjud, chunki ulardan qochish kerak boʻlgan hech qanday klapinyoʻq<ref name="Hillier"/>. Bu dvigatel orqali gaz oqimini yaxshilaydi, quvvatni oshiradi va yoqilgʻi samaradorligini oshiradi.

=== Yagona yuqori gaz taqsimlash vali (SOHC) ===
[[Fayl:Dolomite_Sprint_Valves_Section.jpg|thumb|SOHC dizayni (1973-yilgi Triumph Dolomite Sprint uchun)]]
Yuqori gaz taqsimlash vali dvigatelining eng qadimgi konfiguratsiyasi ''bitta gaz taqsimlash vali'' (SOHC) dizaynidir<ref name="Hillier"/>. SOHC dvigateli silindrlar qatoriga bitta gaz taqsimlash valiga ega, shuning uchun toʻgʻri dvigatelda jami bitta gaz taqsimlash vali va V yoki tekis dvigatelda jami ikkita gaz taqsimlash vali (har bir silindr qatori uchun bittadan) mavjud.

Koʻpgina SOHC dvigatellarida har bir silindrda ikkita valf mavjud{{Efn|However a few engines, such as the 1973 [[Triumph slant-four engine#Sprint 16-valve engine|Triumph Dolomite Sprint engine]] and [[Honda J engine|Honda J Series V6 Engine]] were a SOHC configuration with four valves per cylinder. This was achieved by the camshaft being located in the center of the cylinder head, with equal length rocker arms actuating the intake and exhaust valves.<ref>{{jurnal manbasi|last= Heseltine|first= Richard|title= Triumph Dolomite Sprint|journal= [[Motor Sport (jurnal)|Motor Sport]]|date= 2010-yil iyun|volume= 86|issue= 6|page= 122|editor-last= Roebuck|editor-first= Nigel|issn= 0027-2019|location= London, UK|url= http://www.motorsportmagazine.com/archive/article/june-2010/122/triumph-dolomite-sprint|access-date= 29 March 2015}}</ref> This arrangement was used to provide four valves per cylinder while minimising the valvetrain mass and minimising the overall engine size.<ref>{{jurnal manbasi|last= Lewis|first= Jimmy|title= New for '02: Honda CR250R CRF450R|journal= [[Cycle World]]|page= 62|date= 2001-yil noyabr|volume= 40|issue= 11|editor-last= Edwards|editor-first= David|issn= 0011-4286|publisher= Hachette-Filipacchi Magazines|url= {{Google books|NKRYLxEd6uAC|Cycle World Magazine Jan-Jul 2001|page=RA12-PA62|plainurl=yes}}|access-date=2-yanvar 2015-yil}}</ref><ref>{{veb manbasi|url= http://powersports.honda.com/experience/articles/090111c0811a9fc2.aspx|title= How It Works: Honda Unicam® Engines|website= www.honda.com|date= 23-yanvar 2013-yil|access-date= 2-yanvar 2015-yil|url-status= dead|archive-url= https://web.archive.org/web/20140222215132/http://powersports.honda.com/experience/articles/090111c0811a9fc2.aspx|archive-date= 22 February 2014}}</ref><ref>{{veb manbasi |url= http://www.moto123.com/motorcycle-reviews/article,2010-honda-vfr1200a-first-ride.spy?artid=112508|title= 2010 Honda VFR1200A First Ride |website=www.moto123.com |access-date= 2-yanvar 2015-yil|date= 19-oktabr 2009-yil|url-status= live|archive-url= https://web.archive.org/web/20150102212534/http://www.moto123.com/motorcycle-reviews/article,2010-honda-vfr1200a-first-ride.spy?artid=112508|archive-date= 2 January 2015}}</ref>}}. Gaz taqsimlash valining harakati odatda toʻgʻridan-toʻgʻri (kran yordamida) yoki bilvosita klapanlarga uzatiladi<ref name="Hillier">{{Kitob manbasi|last=Hillier|first=V.A.W.|title=Fundamentals of Motor Vehicle Technology|edition=6th|year=2012|origyear=First published 1966|publisher=Nelson Thornes Ltd|others=In association with: ([[Institute of the Motor Industry|IMI]])|isbn=9781408515181|chapter=2}}</ref>.

=== Ikki tomonlama gaz taqsimlash vali (DOHC) ===
[[Fayl:DOHC-Zylinderkopf-Schnitt.jpg|thumb|DOHC dizayni (V12 dvigateli uchun)]]
''Ikkita yuqori kamerali'', ''ikkita yuqori kamerali'' yoki ''ikkita kamerali'' dvigatel silindr boshining har bir qirgʻogʻida ikkita gaz taqsimlash valiga ega<ref name="Hillier"/><ref name="Stoakes"/>, biri kirish klapanlari uchun, ikkinchisi esa chiqarish klapanlari uchun. Shuning uchun tekis dvigatel uchun ikkita gaz taqsimlash vali va V dvigateli yoki tekis dvigatel uchun jami toʻrtta gaz taqsimlash vali mavjud.

V dvigateli yoki tekis dvigatel DOHC dvigateli sifatida ishlashi uchun toʻrtta gaz taqsimlash vali talab qilinadi, chunki jami ikkita gaz taqsimlash valiga ega boʻlsa, bu dvigatel sxemalari uchun bitta silindr qatoriga faqat bitta gaz taqsimlash vali boʻladi. Toʻrtta gaz taqsimlash vali boʻlgan baʼzi V dvigatellari „toʻrt kamerali“ dvigatellar sifatida sotilgan<ref>{{Veb manbasi|sarlavha=Technically Interesting: Ford Indy DOHC V8|url=https://bringatrailer.com/2018/04/26/technically-interesting-ford-indy-dohc-v8/|ish=The best vintage and classic cars for sale online {{!}} Bring a Trailer|qaralgan sana=6-sentabr 2022-yil|sana=26-aprel 2018-yil}}</ref>, biroq texnik jihatdan „toʻrt kamerali“ silindrli tsilindr uchun toʻrtta gaz taqsimlash vali (yaʼni jami sakkizta gaz taqsimlash vali) talab qiladi, shuning uchun bu dvigatellar faqat ''ikkita yuqori gaz taqsimlash validir''. Terminologiyani yanada chalkashtirib yuborish uchun baʼzi SOHC yassi egizak va V-egizak mototsikl dvigatellari (masalan, Harley-Davidson, Indian, Riley Motors va Triumph tomonidan) notoʻgʻri „egizak kamerali“ dvigatellar sifatida sotilgan.

Koʻpgina DOHC dvigatellarida har bir silindrda toʻrtta valf mavjud{{Efn|However DOHC engines with two valves per cylinder include the [[Alfa Romeo Twin Cam engine]], the [[Jaguar XK6 engine]], the early [[Ford I4 DOHC engine]] and the [[Lotus-Ford Twin Cam|Lotus Ford Twin Cam engine]].}}. Gaz taqsimlash valing chain odatda klapanlarni toʻgʻridan-toʻgʻri chelak krani orqali boshqaradi. DOHC dizayni SOHC dvigatellariga qaraganda qabul qilish va chiqarish klapanlari oʻrtasida kengroq burchakka imkon beradi, bu esa havo-yonilgʻi aralashmasining dvigatel orqali oqishini yaxshilaydi. Yana bir afzalligi shundaki, yondirish shamni eng maqbul joyga qoʻyish mumkin, bu esa oʻz navbatida yonish samaradorligini oshiradi.

== Komponentlar ==

=== Tasmali uzatmalar / zanjirli uzatmalar ===
[[Fayl:Replacing_a_timing_belt.jpg|thumb|Oʻrnatish vaqtida kauchuk vaqt kamari]]
Gaz taqsimlash vali (lar) ning aylanishi tirsakli val tomonidan boshqariladi. <nowiki>XXI</nowiki> asrning koʻplab dvigatellari gaz taqsimlash valini boshqarish uchun kauchuk va kevlardan tayyorlangan tishli kamarda foydalanadi<ref name="Hillier"/><ref name="dansmc.com">{{Veb manbasi|url=http://www.dansmc.com/camchain.htm|sarlavha=Dan's motorcycle 'Cam Drives'|ish=www.dansmc.com|qaralgan sana=29-avgust 2012-yil}}</ref>. Tasmali uzatmalar arzon, minimal shovqin chiqaradi va moylash kerak emas<ref name="Decker">{{jurnal manbasi |last=Decker |first1=John |title=Saturday Mechanic: Replacing Your Timing Belt |journal=[[Popular Mechanics]] |date=1993-yil iyun |volume=170 |issue=6 |issn=0032-4558 |url={{Google books|JOQDAAAAMBAJ|Popular Mechanics Jun 1993|page=93|plainurl=yes}} |access-date=1-mart 2015-yil |editor-last=Oldham |editor-first=Joe |publisher=Hearst |place=New York, NY US}}</ref>. : 93 Tasmali uzatmalarining kamchiliklari — tasmali uzatmalarni muntazam ravishda almashtirish zarurati<ref name="Decker" />; : 94 tavsiya etilgan kamar muddati odatda taxminan {{Convert|50000|-|100000|km|abbr=on|mi}} 000 orasida oʻzgarib turadi<ref name="Decker" />. : 94-95<ref name="Dorries">{{Kitob manbasi|last=Dorries|first=Elisabeth H.|title=TechOne: Automotive Engine Repair|url={{Google books|KsYFA0skuZ8C|TechOne: Automotive Engine Repair|page=250|plainurl=yes}}|accessdate=1-mart 2015-yil|publisher=Thompson Delmar Learning|location=Clifton Park, NY US|year=2005|isbn=1-4018-5941-0}}</ref> : 250 Tasmali uzatmni oʻz vaqtida almashtirilmasa va ishlamay qolsa va vosita shovqin mexanizmi boʻlsa, dvigatelning katta shikastlanishi mumkin.

Yuqori gaz taqsimlash vallarni haydash uchun vaqt kamarlarining birinchi mashhur avtomobil qoʻllanishi Qoʻshma Shtatlardagi SCCA H-modifikatsiyalangan poyga seriyalari uchun 1953-yilda ishlab chiqarilgan Devin-Panhard poygalari edi<ref name="Pace&Brinker">{{Kitob manbasi|last=Pace|first=Harold W.|title=Vintage American Road Racing Cars 1950-1969|year=2004|page=62|publisher=MotorBooks International|location=St. Paul MN US|isbn=0-7603-1783-6|url={{Google books|oZempfWXoe4C|Vintage American Road Racing Cars 1950-1969 |plainurl=yes}}|accessdate=27-fevral 2015-yil}}</ref>. : 62 Ushbu dvigatellar Panhard OHV tekis egizak dvigatellariga asoslangan boʻlib, ular Norton mototsikl dvigatellari qismlaridan foydalangan holda SOHC dvigatellariga aylantirildi<ref name="Pace&Brinker" />. : 62 Tasmali uzatmadan foydalangan birinchi ishlab chiqarish avtomobili 1962-yilgi Glas 1004 ixcham kupesi edi<ref>{{Kitob manbasi|last=Norbye|first=Jan P.|title=BMW - Bavaria's Driving Machines|year=1984|publisher=Publications International|location=Skokie, IL|isbn=0-517-42464-9|chapter=Expanding on Excellence: The 5-Series and 3-Series|page=[https://archive.org/details/bmwbavariasdrivi00norb/page/191 191]|chapterurl=https://archive.org/details/bmwbavariasdrivi00norb/page/191}}</ref>.

Zamonaviy dvigatellarda keng tarqalgan boʻlib qoʻllanadigan boshqa gaz taqsimlash vali qoʻzgʻaysan usuli, bir yoki ikki qatorli metall [[roller]]zanjirlardan qurilgan zanjirli uzatmadir<ref name="Hillier"/><ref name="dansmc.com"/>. 1960-yillarning boshlariga kelib, koʻpgina ishlab chiqarilgan avtomobillarning yuqori gaz taqsimlash vali konstruktsiyalarida gaz taqsimlash vali (lar)ni boshqarish uchun zanjirlar ishlatilgan<ref name="Boddy">{{jurnal manbasi|last=Boddy|first1=William|author-link=Bill Boddy|url=http://www.motorsportmagazine.com/archive/article/january-1964/17/random-thoughts-about-ohc|title=Random Thoughts About O.H.C.|journal=[[Motor Sport (jurnal)|Motor Sport]]|date=1964-yil yanvar|volume=XL|issue=1|publisher=Teesdale Publishing|place=London, UK}}</ref>. : 17 Vaqt zanjirlari odatda vaqti-vaqti bilan almashtirishni talab qilmaydi, ammo kamchiliklari shundaki, ular vaqt kamarlaridan koʻra shovqinliroqdir<ref name="Dorries"/>. : 253 

=== Tishli uzatmalar ===
Tirsakli val va gaz taqsimlash vali oʻrtasidagi tishli uzatma tizimi odatda ogʻir yuk mashinalarida ishlatiladigan dizel yuqori gaz taqsimlash vali dvigatellarida qoʻllanadi<ref>{{Kitob manbasi|last=Bennett|first=Sean|title=Modern Diesel Technology: Diesel Engines|pages=88–89, 362|publisher=Cengage Learning|location=Stamford, CT US|isbn=978-1-285-44296-9|url={{Google books|8OzKAgAAQBAJ|Modern Diesel Technology: Diesel Engines|page=88|plainurl=yes}}|accessdate=4-yanvar 2015-yil|quote=In most commercial diesels, OHCs are gear-driven.|date=1-yanvar 2014-yil}}</ref>. Tishli uzatmalar odatda yengil yuk mashinalari yoki avtomobillar uchun dvigatellarda qoʻllanilmaydi<ref name="Hillier"/>.

=== Boshqa gaz taqsimlash vali haydovchi tizimlari ===
[[Fayl:Norton_No66,_pic-003.JPG|thumb|Norton mototsikl dvigateli burchakli mil bilan boshqariladigan gaz taqsimlash vali]]
1950-yillarga qadar bir nechta OHC dvigatellari gaz taqsimlash vali haydash uchun konusli tishli uzatmadan foydalangan. Masalan, 1908—1911-yillardagi Maudslay 25/30<ref>{{jurnal manbasi|last=Boddy|first1=William|author-link=Bill Boddy|title=An Edwardian Overhead-Camshaft 25/30 Maudslay|journal=[[Motor Sport (jurnal)|Motor Sport]]|page=909|url=http://www.motorsportmagazine.com/archive/article/august-1972/68/edwardian-overhead-camshaft-2530-maudslay|access-date=6 February 2015|date=1972-yil avgust|volume=XLVIII|issue=8|editor-last=Boddy|editor-first=William|publisher=Teesdale Publishing|place=London, UK|archiveurl=https://web.archive.org/web/20150206033639/http://www.motorsportmagazine.com/archive/article/august-1972/68/edwardian-overhead-camshaft-2530-maudslay|archivedate=6 February 2015}}</ref><ref name="Culshaw">{{Kitob manbasi|last=Culshaw|first=David|year=2013|origyear=1974|chapter=Maudslay|title=The Complete Catalogue of British Cars 1895 - 1975|edition=e-book|location=Poundbury, Dorchester, UK|publisher=Veloce Publishing|page=210|isbn=978-1-845845-83-4}}</ref>, Bentley 3 Litr<ref>{{Kitob manbasi|last=Norbye|first=Jan P.|title=The complete handbook of automotive power trains|page=318|publisher=Tab Books|year=1981|isbn=0-8306-2069-9|url={{Google books|YSpKEyATeM8C|The complete handbook of automotive power trains|page=318|plainurl=yes}}|accessdate=7-yanvar 2015-yil}}</ref>, 1929—1932-yillardagi MG Midget, 1925-1948 yillardagi Velocette K seriyasi<ref>{{jurnal manbasi|last=Cameron|first1=Kevin|author-link=Kevin Cameron (jurnalist)|title=TDC: Little things|journal=[[Cycle World]]|date=2004-yil mart|volume=43|issue=3|issn=0011-4286|page=14|url={{Google books|VYB28ExdkSMC|Cycle World Magazine Jan 2004|page=RA2-PA22|plainurl=yes}}|access-date=7-yanvar 2015-yil}}</ref>, 1931—1957-yillardagi Norton International va 1947—1962-yillardagi Norton Manx<ref>{{Kitob manbasi|last=Wilson|first=Hugo|title=The Encyclopedia of the Motorcycle|url=https://archive.org/details/encyclopediaofmo00wils_1|year=1995|publisher=Dorling Kindersley|location=London, UK|isbn=0-7513-0206-6|page=[https://archive.org/details/encyclopediaofmo00wils_1/page/144 144]|chapter=The A-Z of Motorcycles}}</ref>. Soʻnggi paytlarda 1950—1974-yillardagi Ducati Single<ref>{{Kitob manbasi|last=Walker|first=Mick|authorlink=Mick Walker (motorcycling)|title=Ducati Singles Restoration|chapter=4 Engine|page=48|year=2003|origyear=1991|publisher=Motorbooks International|location=St. Paul, MN US|isbn=0-7603-1734-8|url={{Google books|JaXQtjcbmC4C|Ducati Singles Restoration|page=48|plainurl=yes}}|accessdate=4-yanvar 2015-yil|chapterurl={{Google books|JaXQtjcbmC4C|Ducati Singles Restoration|page=32|plainurl=yes}}}}</ref>, 1973—1980-yillardagi Ducati L-twin dvigateli, 1999—2007-yillardagi Kawasaki W650 va 2011—2016-yillardag Kawasaki W800 mototsikl dvigatellarida konusli vallar ishlatilgan<ref>{{Veb manbasi|url=http://www.kawasaki.eu/en/products/sports/2015/w800_/overview?Uid=096BDlgLWQ0JWAldClhcXAsMWwoMCVlcXgteXwoLC1BaUQw|sarlavha=2015 W800|ish=www.kawasaki.eu|qaralgan sana=19-dekabr 2019-yil|arxivsana=2022-11-10|arxivurl=https://web.archive.org/web/20221110190009/https://www.kawasaki.eu/en/products/sports/2015/w800_/overview?Uid=096BDlgLWQ0JWAldClhcXAsMWwoMCVlcXgteXwoLC1BaUQw}}</ref><ref>{{Yangiliklar manbasi |last=Ash |first=Kevin |author-link=Kevin Ash |date=26-oktabr 2011-yil |title=Kawasaki W800 review |work=[[The Daily Telegraph|The Telegraph]] |url=https://www.telegraph.co.uk/motoring/motorbikes/8833767/Kawasaki-W800-review.html |url-status=live |archive-url=https://web.archive.org/web/20130621065158/http://www.telegraph.co.uk/motoring/motorbikes/8833767/Kawasaki-W800-review.html |archive-date=21-iyun 2013-yil}}</ref>. Crosley toʻrt silindrli 1946-yildan 1952-yilgacha gaz taqsimlash valni haydash uchun mil minorasi dizaynidan foydalangan oxirgi avtomobil dvigateli edi; Crosley dvigatel formatiga boʻlgan huquqlarni bir nechta turli kompaniyalar, jumladan 1952-yilda General Tire, 1955-yilda Fageol, 1959-yilda Crofton, 1961-yilda Homelite va 1966-yilda Fisher Pirs, Crosley avtomobil zavodi eshiklarini yopganidan keyin sotib oldi va ular yana bir necha yil bir xil dvigatelni ishlab chiqarishni davom ettirdilar.

1920—1923-yillarda Buyuk Britaniyada ishlab chiqarilgan Leyland Eight hashamatli avtomobilida parallel ravishda uchta krank va rodlar toʻplamidan foydalanadigan gaz taqsimlash vali haydovchisi ishlatilgan<ref name="WBMarch74">{{jurnal manbasi|title=How Did The Leyland Eight Rate?|last=Boddy|first1=William|author-link=Bill Boddy|page=230|journal=[[Motor Sport (jurnal)|Motor Sport]]|volume=L|issue=3|editor-last=Boddy|editor-first=William|date=1974-yil mart|url=http://www.motorsportmagazine.com/archive/article/march-1974/38/how-did-leyland-eight-rate|access-date=3 January 2015}}</ref>. Shunga oʻxshash tizim 1926—1930-yillardagi Bentley Speed Six va 1930—1932-yillardagi Bentley 8 Literda ishlatilgan<ref name="WBMarch74" /><ref>{{jurnal manbasi|last=Brooks|first1=Philip C.|editor1-last=Carpenter|editor1-first=Rhonda|editor2-last=Iwalani|editor2-first=Kahikina|year=2009|title=The Mighty Sixes|journal=The International Club for Rolls-Royce & Bentley Owners Desk Diary 2010|pages=27, 32|place=Tampa, FL USA|publisher=Faircount}}</ref>. Ikkala uchida ham qarshi ogʻirliklarga ega boʻlgan ikki rodli tizim 1958—1973-yillardagi [[NSU Prinz]] ning koʻplab modellari tomonidan ishlatilgan<ref name="Boddy"/>.{{clear right}}

== Tarixi ==

=== 1900—1914-yillar ===
Birinchi gaz taqsimlash vali dvigatellari orasida 1902-yilda Buyuk Britaniyada ishlab chiqarilgan Maudslay SOHC dvigateli bor edi<ref name="Culshaw"/> : 210<ref name="Boddy"/> : 906<ref>{{Ensiklopediya manbasi|title=Maudslay|last=Georgano|first=G. N.|authorlink=G. N. Georgano|page=[https://archive.org/details/newencyclopediao0000unse_v2r4/page/407 407]|encyclopedia=The New Encyclopedia of Motorcars 1885 to the Present|editor-last=Georgano|editor-first=G. N.|year=1982|origyear=1968|publisher=E. P. Dutton|location=New York|edition=Third|isbn=0525932542|lccn=81-71857|ref=none|url=https://archive.org/details/newencyclopediao0000unse_v2r4/page/407}}</ref> va 1903-yilda AQShda ishlab chiqarilgan Marr Auto Car SOHC dvigateli<ref name="Marr Auto Car Company">{{Veb manbasi|url=http://www.marrautocar.com/Marr_Auto_Car_Company/Welcome.html|ish=www.marrautocar.com|sarlavha=Marr Auto Car Company|arxivurl=https://web.archive.org/web/20180411094907/http://marrautocar.com/Marr_Auto_Car_Company/Welcome.html|arxivsana=11 April 2018}}</ref><ref name="Kimes">{{Kitob manbasi|last=Kimes|first=Beverly Rae|title=Walter L Marr: Buick's Amazing Engineer|url=https://archive.org/details/walterlmarrbuick0000kime|year=2007|publisher=Racemaker Press|isbn=978-0976668343|page=[https://archive.org/details/walterlmarrbuick0000kime/page/n49 40]}}</ref>. Birinchi DOHC dvigateli Peugeot inline-toʻrt poyga dvigateli boʻlib, u 1912-yilda [[Fransiya]] Gran-prisida gʻolib chiqqan avtomobilni quvvatlantirdi. DOHC dvigateliga ega yana bir Peugeot 1913-yilgi Fransiya Gran-prisida gʻolib chiqdi, undan keyin SOHC dvigatelli ''Mercedes-Benz 18/100 GP'' 1914-yilgi Fransiya Gran-prisida gʻolib chiqdi.

Isotta Fraschini Tipo KM — Italiyada 1910—1914-yillarda ishlab chiqarilgan — SOHC dvigatelidan foydalangan birinchi seriyali avtomobillardan biri edi<ref>{{Veb manbasi|sarlavha=1913 Isotta Fraschini 100-120 hp Tipo KM 4 Four-Seat Torpedo Tourer - Auction Lot|url=http://www.motorbase.com/auctionlot/profile/2008/08/15/316-1913-isotta-fraschini-100-120-hp-tipo-km-4-four-seat-torpedo-tourer/|ish=www.motorbase.com|kirish sanasi=29-dekabr 2019-yil|qaralgan sana=2022-11-10|arxivsana=2020-10-09|arxivurl=https://web.archive.org/web/20201009151318/http://www.motorbase.com/auctionlot/profile/2008/08/15/316-1913-isotta-fraschini-100-120-hp-tipo-km-4-four-seat-torpedo-tourer/}}</ref>.

=== Birinchi jahon urushi ===
[[Fayl:Napier_Lion_cambox.jpg|thumb|1917-1930-yillardagi Napier Lion samolyot dvigatelining DOHC silindr boshi]]
[[Birinchi jahon urushi]] davrida ittifoqdosh va [[markaziy kuchlar]]; Xususan, [[Germaniya imperiyasi]]ning ''Luftstreitkräfte'' havo kuchlari harbiy samolyot dvigatellari uchun mototsikl dvigatellarining yuqori egaz taqsimlash vali texnologiyasini tezda qoʻllashga harakat qilishdi. ''Mercedes 18/100 GP'' avtomobilining SOHC dvigateli (1914-yilgi Fransiya Gran-prisida gʻolib chiqqan) Mercedes va Rolls Royce samolyot dvigatellari uchun boshlangʻich nuqtaga aylandi. Mercedes olti silindrli dvigatellar seriyasini yaratdi, ular Mercedes D.III bilan yakunlandi. Rolls Royce urush boshida Angliyada qoldirilgan poyga avtomobili asosida Mersedes silindr boshi dizaynini teskari muhandislik bilan ishlab chiqdi va bu Rolls-Royce Eagle V12 dvigateliga olib keldi. Boshqa SOHC konstruksiyalari qatoriga ispancha Hispano-Suiza 8 V8 dvigateli, American Liberty L-12 V12 dvigateli kiritilgan boʻlib, ular keyingi Mercedes D.IIIa dizaynining qisman ochilgan SOHC klapan konstruksiyasiga yaqindan amal qilgan; va Max Friz — ishlab chiqilgan; Nemis BMW IIIa toʻgʻridan-toʻgʻri oltita dvigatel. DOHC Napier Lion W12 dvigateli 1918-yildan boshlab Buyuk Britaniyada ishlab chiqarilgan.

Ushbu dvigatellarning aksariyati haydovchini krank milidan dvigatelning yuqori qismidagi gaz taqsimlash valiga oʻtkazish uchun mildan foydalangan. Katta samolyot dvigatellari, ayniqsa havo bilan sovutilgan dvigatellar, ish sharoitida silindr blokining balandligi oʻzgarishiga olib keladigan sezilarli issiqlik kengayishini boshdan kechirdilar. Ushbu kengayish pushrodli dvigatellar uchun qiyinchiliklarga olib keldi, shuning uchun toymasin splineli milya haydovchisidan foydalanadigan yuqori gaz taqsimlash vali dvigateli bu kengayishni taʼminlashning eng oson yoʻli edi. Ushbu burchakli vallar odatda blokdan tashqaridagi tashqi trubkada boʻlib, „minora shaftalari“ deb nomlanardi<ref>{{Kitob manbasi|last=Thorpe|first=Leslie Aaron|title=A text book on aviation: the new cadet system of ground school training|pages=14–15|year=1936|publisher=Aviation Press|url={{Google books|aVluAAAAIAAJ|A text book on aviation: the new cadet system of ground school training, Volume 3|page=14|plainurl=yes}}|accessdate=27-fevral 2015-yil|quote=The overhead camshafts are driven by bevel gears and vertical shafts known as tower shafts.}}</ref>.

=== 1919—1944-yillardagi ===
[[Fayl:1933_Bugatti_Type_59_Grand_Prix_engine.jpg|right|thumb| 1933 yil Bugatti Type 59 toʻgʻridan-toʻgʻri sakkizta gran-pri poyga dvigateli]]
Amerikaning dastlabki gaz taqsimlash vali ishlab chiqarish dvigateli 1921—1926-yillardagi Duesenberg Model A hashamatli avtomobilida ishlatilgan SOHC toʻgʻri sakkiz dvigateli edi<ref>{{Kitob manbasi|last=Mueller|first=Mike|year=2006|chapter=Chapter 6 - Chariot of the Gods Duesenberg Straight Eight|chapterurl={{Google books|69qYnoohrMYC|American Horsepower: 100 Years of Great Car Engines|page= 49|plainurl= yes}}|title=American Horsepower 100 Years of Great Car Engines|url={{Google books|69qYnoohrMYC|American Horsepower: 100 Years of Great Car Engines|page=51|plainurl= yes}}|location=St. Paul, MN USA|publisher=Motorbooks|pages=51|isbn=978-0-7603-2327-4|accessdate=2-fevral 2015-yil}}</ref>.

1926-yilda Sunbeam 3 litrli Super Sports DOHC dvigatelidan foydalanadigan birinchi ishlab chiqarilgan avtomobilga aylandi<ref name="Autocar197710">{{jurnal manbasi|journal=[[Autocar (jurnal)|Autocar]]|volume=147 (nbr 4221)|title=Talking of sports cars: Sunbeam three-litre|pages=69–71|date=1-oktabr 1977-yil}}</ref><ref>{{Kitob manbasi|last=Georgano|first=G.N.|title=Cars: Early and Vintage, 1886-1930|date=1985|publisher=Grange-Universal|location=London}}</ref>.

Qoʻshma Shtatlarda Duesenberg DOHC dvigatellarini (mavjud SOHC dvigatellari bilan bir qatorda) DOHC toʻgʻridan-toʻgʻri sakkiz dvigateli bilan jihozlangan Duesenberg Model J ning 1928-yilda chiqarilishi bilan qoʻshdi. 1931—1935-yillar Stutz DV32 DOHC dvigatelidan foydalanish uchun yana bir erta Amerika hashamatli avtomobili edi. Shuningdek, Qoʻshma Shtatlarda DOHC Offenhauser poyga dvigateli 1933-yilda taqdim etilgan. Ushbu inline-toʻrt dvigatel 1934-yildan 1970-yilgacha [[Shimoliy Amerika]] ochiq gʻildirakli poygada ustunlik qildi.

Boshqa dastlabki SOHC avtomobil dvigatellari 1920—1923-yillardagi Wolseley Ten, 1928—1931-yillardagi MG 18/80, 1926—1935-yillardagi Singer Junior va 1928-1929 yillardagi Alfa Romeo 6C Sport edi. Dastlabki eksantrik mili mototsikllariga 1925-1949 yillardagi Velocette K seriyasi va 1927—1939-yillardagi Norton CS1 kiradi.

=== 1945-yildan — hozirgi kungacha ===
[[Fayl:1948_Crosley_COBRA_engine_OHC.jpg|right|thumb| 1946-1949-yillardagi Crosley CoBra SOHC dvigateli]]
1946—1948-yillardagi Crosley CC Four, shubhasiz, SOHC dvigatelidan foydalangan holda Amerikada ommaviy ishlab chiqarilgan birinchi avtomobil edi<ref name="Simanaitis">{{jurnal manbasi|last=Simanaitis|first1=Dennis|title=Tech Tidbits|url=https://archive.org/details/sim_road-track_1994-02_45_6/page/121|journal=[[Road & Track]]|date=1994-yil yanvar|page=121|editor-last=Bryant|editor-first=Thos L.|publisher=Hachette Filipacchi Magazines|place=Newport Beach, CA US|volume=45|issue=6|issn=0035-7189}}</ref><ref>{{Veb manbasi|url=http://crosleyautoclub.com/EngineTree/Crosley_Eng_Tree.html|sarlavha=Crosley Engine Family Tree - Taylor Years|ish=www.crosleyautoclub.com|qaralgan sana=19-dekabr 2019-yil}}</ref><ref>{{Veb manbasi|url=http://crosleyautoclub.com/EngineTree/Crosley_Eng_Tree-1.html|sarlavha=Crosley Engine Family Tree - CoBra Years|ish=www.crosleyautoclub.com|qaralgan sana=19-dekabr 2019-yil}}</ref>. Ushbu kichik ommaviy ishlab chiqarish dvigateli 1950-yilgi 12 soatlik Sebring gʻolibiga quvvat berdi<ref name="Simanaitis" />. {{Rp|page=121}}

DOHC konfiguratsiyasidan foydalanish Ikkinchi jahon urushidan keyin sport avtomobillaridan boshlab asta-sekin oʻsib bordi. Ushbu davrning mashhur DOHC dvigatellari qatoriga 1948—1959-yillardagi Lagonda toʻgʻridan-toʻgʻri oltita dvigateli, 1949—1992-yillardagi Jaguar XK toʻgʻridan-toʻgʻri oltitali dvigateli va 1954-1994 yillardagi Alfa Romeo Twin Cam inline-toʻrt dvigateli kiradi<ref name="EuropeanCarWeb.com">{{Veb manbasi|url=http://www.europeancarweb.com/features/0209ec_twin_cam_analysis/index.html|sarlavha=An Echo of the Past — the history and evolution of twin-cam engines|sana=2009-yil fevral|qaralgan sana=29-avgust 2012-yil|ish=www.EuropeanCarWeb.com|nashriyot=European Car Magazine, Source Interlink Media|arxivurl=https://web.archive.org/web/20120303061544/http://www.europeancarweb.com/features/0209ec_twin_cam_analysis/index.html|arxivsana=3 March 2012}}</ref><ref>{{Veb manbasi|url=http://www.alfisti.co.uk/boxerpage.htm|sarlavha=Technical- Boxer History|ish=www.alfisti.co.uk|arxivurl=https://web.archive.org/web/20130329040043/http://www.alfisti.co.uk/boxerpage.htm|arxivsana=29 March 2013}}</ref>. 1966—2000-yillardagi Fiat Twin Cam inline-toʻrt dvigateli vaqt zanjiri oʻrniga tishli vaqt kamaridan foydalangan birinchi DOHC dvigatellaridan biri edi<ref>{{Veb manbasi|sarlavha=Old Fiat ad with Aurelio Lampredi|url=http://i.kinja-img.com/gawker-media/image/upload/19f9mk0fozzvppng.png|ish=www.kinja-img.com|kirish sanasi=31-yanvar 2015-yil|qaralgan sana=2022-11-10|arxivsana=2020-12-31|arxivurl=https://web.archive.org/web/20201231123240/http://i.kinja-img.com/gawker-media/image/upload/19f9mk0fozzvppng.png}}</ref>.

1980-yillarda yoqilgʻi sarfi va chiqindilarini kamaytirish bilan birga ishlash samaradorligini oshirish zarurati yapon ishlab chiqaruvchilaridan boshlab asosiy transport vositalarida DOHC dvigatellaridan foydalanishni koʻpaytirdi<ref name="EuropeanCarWeb.com"/>. 2000-yillarning oʻrtalariga kelib, koʻpchilik avtomobil dvigatellari DOHC sxemasidan foydalangan.

== Yana qarang ==

* Blokdagi kamera
* Kamerasiz
* Yuqori valfli dvigatel
* Oʻzgaruvchan valf vaqti
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== Izohlar ==
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== Manbalar ==
{{manbalar}}
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[[Turkum:Engine valvetrain configurations]]