Adual-clutch transmission (DCT) (sometimes referred to as atwin-clutch transmission) is a type of multi-speedvehicletransmission system, that uses two separateclutches for odd and evengear sets.[1] The design is often similar to two separatemanual transmissions with their respective clutches contained within one housing, and working as one unit.[2][3] In car and truck applications, the DCT functions as anautomatic transmission, requiring no driver input to change gears.
The first DCT to reach production was theEasidrive automatic transmission introduced on the1961 Hillman Minx mid-size car. This was followed by various eastern European tractors through the 1970s (using manual operation via a single clutch pedal), then thePorsche 962 C racing car in 1985. The first DCT of the modern era was used in the 2003Volkswagen Golf R32. Since the late 2000s, DCTs have become increasingly widespread, and have supplanted hydraulic automatic transmissions in various models of cars.
More generally, a transmission with several clutches can be called amulti clutch transmission. For example, theKoenigsegg Jesko has a transmission with one clutch per gear,[4] making for a total of 7 clutches.[5][6]
The fundamental principle of a DCT is that one clutch drives a gear-set for the even-numbered gears, while the other clutch drives the odd-numbered gears.[1][2][7] Since the DCT can pre-select an odd gear while the vehicle is being propelled in an even gear (or vice versa), DCTs can shift several times faster than is possible with a manual transmission.[3][8] By timing the operation of one clutch to engage at the precise moment that the other is disengaging, a DCT can shift gears without interrupting the torque supply to the wheels.[7][8]
A DCT uses clutch packs (as per a manual transmission), rather than thetorque converter used by traditional (hydraulic) automatic transmissions.[1] The DCT clutches are either "wet" or "dry" and are similar to the clutches used in most motorcycles.[9] Wet-clutches are bathed in oil to provide cooling for the clutch surface,[10] therefore wet-clutches are often used in applications with higher torque loads, such as the 1,250 N⋅m (922 lbf⋅ft) engine in theBugatti Veyron.
Several arrangements for the two clutches are possible, and are outlined below:
The concept of a dual-clutch transmission was invented by French engineerAdolphe Kégresse in 1939.[14] The transmission was intended for use in theCitroën Traction Avant, however Kégresse ran out of money before a working model could be developed.[15]
One of the first production DCTs was theEasidrive unit developed in the late 1950s byUnited Kingdom'sSmiths Industries andRootes. This DCT – introduced on the 1961Hillman Minx (Series IIIC) – used twoelectro-magnetic clutches, along with analogueelectronics and a series ofsolenoids to implement the gear shifts.[16][17] TheEasidrive was offered as an option on Hillman and Singer models, however it was not a reliable device and many were replaced by conventional manual transmissions.
Porsche began development of DCTs for racing cars in the late 1970s,[18] due to the possibility of a DCT preventing a drop in boost during gear shifts on a turbocharged engine.[19][20] As the electronics required to control the transmission became compact enough to be practical, thePorsche Doppelkupplungsgetriebe ('dual-clutch gearbox') (PDK) transmission was installed as a prototype in aPorsche 956 Le Mans racing car in 1983.[2][21] The first use of a PDK in competition was the 1985Porsche 962 C Le Mans racing car, which won theWorld Sportscar Championship in 1986.[2][22] The PDK transmission was also used in the 1985Audi Sport Quattro S1 Group B rally car.[8][23]
The first mass-production passenger car to use a DCT was the 2003Volkswagen Golf R32.[2][7][10]
BorgWarner produced the first mass-production DCT, as used in theR32 model introduced to the Volkswagen Golf range in 2003.[7][10][24] The company have produced many of the DCTs used by theVolkswagen Group (marketed asDSG for Volkswagen-branded cars)[8][25] and produced various components for the 2007Nissan GT-R sports car, an early application for DCTs involving high torque loads.[26] The company supplies several car manufacturers with complete transmission units, wet-clutches and/ormechatronic control modules.[2][1][25][24]
Getrag began production of DCTs in 2008[27] and has supplied manufacturers includingBMW,[28]Dacia,[29]Dodge,Ferrari,[30][31]Mercedes-Benz,[32]Ford,Mitsubishi,Renault,Smart andVolvo.[33] TheGetrag 7DCL750 is a 7-speed DCT which is designed for high-performance engines and has a torque rating of 750 N⋅m (553 lbf⋅ft).[34] It is used in mid-engined sports cars such as the 2009Ferrari 458, the 2014Mercedes-AMG GT and the 2017Ford GT.[35]
Honda manufactures DCTs for some Honda motorcycles as of 2024, and was the first to add a DCT to motorcycles. Honda also previously manufactured DCTs for someAcura cars.
HYUNDAI TRANSYS manufactures dry 7-speed and wet 8-speed DCTs as of 2024. The DCTs are used in some Hyundai and Kia (e.g. Ceed) vehicles.
LuK DCTs have been used by Volkswagen Group since 2008, in several smaller cars with relatively low torque outputs.[36]
Ricardo designed and built 7-speed DCT used by the 2005-2015Bugatti Veyron,[1][2][8][37] which has a turbocharged 16-cylinder engine producing 1,250 N⋅m (922 lbf⋅ft) of torque.
Stellantis manufactures the electrified dual-clutch transmission (eDCT) at theMirafiori Automotive Park in Italy as of 2024.
Tremec provides the 8-speed DCT used in the 2020 Chevrolet Corvette C8 and the 7-speed DCT used in the 2020 Ford Mustang Shelby GT500.[38]
ZF Friedrichshafen produce the 7-speed DCT used by Porsche (marketed asPDK).[39][40][41][42][43]
Following its 2003 introduction in theVolkswagen Golf R32, a 6-speed DCT (model codeDQ250), with two wet-clutches arranged concentrically, has been used in several Volkswagen and Audi models.[10] In 2008, Volkswagen group began production of theDQ200, a 7-speed DCT using two dry-clutches arranged side-by-side (instead of concentrically).[10][2] Volkswagen claims fuel economy improvements of 6% compared with a 6-speed manual and 20% compared with a traditional (hydraulic) automatic transmission.[10] DCT transmissions have been used on vehicles sold by Alfa Romeo, Volkswagen, Audi, Tata Motors, SEAT, Skoda, and Bugatti, mostly marketed using the termDirect-Shift Gearbox (except for Alfa Romeo, which has used the term TCT, also Tata Motors uses the term DCA (Dual Clutch Automatic) and Audi, which has also used the termS-Tronic).[8][44][25]
Usage in high performance cars began in 2005 with the 7-speed DCT used in theBugatti Veyron. Other early high performance applications include the 2007Nissan GT-R,[45][46] the 2008Ferrari California,[47] the 2008Mitsubishi Lancer Evolution X[48][49][50] and the 2009Porsche 911 (997).[51][52]
The 2009Honda VFR1200F is the first motorcycle to use a DCT.[53] Honda has since expanded the application of the DCT to the Gold Wing model (model year 2018), the Africa Twin, the NT1100, Rebel 1100, and the NC700XD (model year 2012).
In 2010, theMitsubishi Fuso 6-speedDuonic transmission became the first DCT to be used in a truck.[54]
The 2015Acura TLX uses atorque converter (a device typically used in hydraulic automatic transmissions) paired with its 8-speed DCT. The purpose of the torque converter is to improve the smoothness of low-speed driving, through the elimination of jolting and shuddering sometimes found in DCTs at low speed.[55]
Several 1970s tractors from eastern European countries (such as theKirovets K-700 derivatives) used manually operated DCTs. For example, theFortschritt ZT 300 has anUnterlastschaltstufe ('shifting under load') function, which needs to be pre-selected by the driver and then activated by pressing the clutch halfway down. This engages the second clutch, which applies a reduction gear to the driven wheels without any interruption in the torque transmission to the wheels.
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A different type of dual-clutch transmission has been used in somerailcars. The two clutches are placed one on the gearbox input shaft and the other on the gearbox output shaft. To make a gear change, both clutches disengage simultaneously and a brake inside the gearbox engages. The gearchange occurs with all gears stationary, so nosynchronizing mechanism is needed. After the gear change, both clutches re-engage. There is a significant break in power transmission, so this system is unsuitable forshunting locomotives.
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