Theautomated manual transmission (AMT) is a type oftransmission formotor vehicles. It is essentially a conventionalmanual transmission[1][2][3][4][5] equipped with automatic actuation to operate theclutch and/or shiftgears.
Many early versions of these transmissions that aresemi-automatic in operation, such asAutostick, which automatically control only theclutch – often using various forms of clutchactuation, such aselectro-mechanical,hydraulic,pneumatic, orvacuum actuation[6][7] – but still require the driver's manual input and full control to initiate gear changes by hand. These systems that require manual shifting are also referred to asclutchless manual systems.[8] Modern versions of these systems that arefully automatic in operation, such asSelespeed andEasytronic, can control both the clutch operation and the gear shifts automatically, by means of anECU, therefore requiring no manual intervention or driver input for gear changes.[9][10]
The usage of modern computer-controlled AMTs in passenger cars increased during the mid-1990s, as a more sporting alternative to the traditional hydraulic automatic transmission. During the 2010s, AMTs were largely replaced by the increasingly widespreaddual-clutch transmission, but remained popular for smaller cars inEurope and somedeveloping markets, particularlyIndia, where it is notably favored over conventional automatic andCVT transmissions due to its lower cost.[11]
Automated manual transmissions can besemi-automatic orfully-automatic in operation. Several different systems to automate the clutch and/or shifting have been used over the years, but they will generally use one of the following methods of actuation for the clutch and/or shifting:hydraulic orelectro-hydraulicactuation,[12]electro-mechanical,[13]pneumatic,[6][14][15]electromagnetic,[16][17][18] or even purelyelectrical using anelectric motor.
Gear shifting, clutch actuation, shift-timing, and rev-matching are all under automated control via electronic sensors, computers, and actuators.[13][19] When shifting gears, the driver selects the desired gear with thetransmission shift lever, while electronic sensors and actuators connected to aTCU (transmission computer) ormicroprocessor will automatically operate the clutch and throttle to match revs and to re-engage the clutch in milliseconds. Torque and power transfer to the drive wheels will also be electronically controlled. Most modern implementations of this transmission function are in a sequential mode, where the driver can upshift or downshift by only one gear at a time. However, this is not the case for all modern transmissions. For example, BMW's "SMG" and Ferrari's "F1" transmission can skip gears on both downshifts and upshifts, when selecting gears manually via the steering wheel-mounted paddle-shifters, as seen on most modern transmissions. Older clutchless manual transmissions (mostly prior to the 1990s) will retain H-pattern shifters, plus the shift gate, and will require the driver to select the required gear ratios manually. The clutch, however, will be aservo-controlled unit, connected to variousactuators, asolenoid andsensors which control the clutch automatically.
Another alternate means of clutchautomation is the "clutch-by-wire" system. The system generally uses anelectricactuator andelectronic sensors, which replace the mechanical clutch linkage or hydraulic clutch connection, to monitor and control clutch positioning, completely replacing the hydraulic linkage between the mechanical clutch and pedal itself with a single electro-mechanical actuator.[20][21][22]
Depending on the mechanical build and design, some (mostly modern) automated manual transmissions will automatically shift gears at appropriate points (like a conventionalautomatic transmission), while traditionalsemi-automatic and clutchless manuals require the driver to manually select the gear even when the engine is at redline, since they automate only part of the transmission (namely the clutch), and will not shift gears by themselves.[23] Despite the superficial similarity, automated manual transmissions differ significantly in internal operation and driver's "feel" from amanumatic, the latter of which is anautomatic transmission (automatics use atorque converter instead of a clutch like in an automated manual, to manage the mechanical linkage between the transmission and motor) with the ability to override the automatic transmission's computer, and actuate shifts manually.[24]
Add-on AMTs can also function as a regular manual gearbox (with a manual shift lever), whereas integrated AMTs do not need a "normal" shift layout, so they can be designed with an optimized AMT shifting layout (which would have an unusual pattern to manually shift). Integrated AMTs either have gear-selector drums (which allows only serial shifting and no gear-skipping, but this system is fairly inexpensive, because it needs only one actuator), or single actuators. Single-actuator systems require one actuator for each shifting sleeve (which is why this type of system is more expensive, but it also shifts faster). The actuators can either be electro-hydraulic (more expensive, but faster, well-suited for single-actuator systems, and allow for higher torque), orelectro-mechanical (less expensive, but usually limited to 250N·m (184.5lb-ft) of gearbox input torque). This limit is because the clutch actuation force increases with higher torque, and short shifting times; electro-mechanical actuators are justelectric motors – using larger motors reduces the motor dynamics due to the motors' higher mass moment of inertia (which is not good for fast shifting), and bigger motors also put more stress on the car's 12-volt electrical system. As a result, one can have either slow shifting and a very large lead-acid battery (not suitable for cars), or fast shifting and a smaller battery (works up to 250 N·m of torque).
Modern AMTs, such as SuzukiAuto Gear Shift and Dacia/RenaultEasy-R, usually operate in conjunction withelectronic throttle control to initiate gear shifts based on certain RPM and/or throttle position.
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The automated manual transmission has its origins in earlyclutchless manual transmissions that began to appear on mass-production cars in the 1940s and 1950s. An early example of this transmission was introduced with theHudson Commodore in 1942, calledDrive-Master. This unit was an earlysemi-automatic transmission, based on the design of a conventional manual transmission which used a servo-controlled vacuum-operated clutch system, with three different gear shifting modes, at the touch of a button; manual shifting and manual clutch operation (fully-manual), manual shifting with automated clutch operation (semi-automatic), and automatic shifting with automatic clutch operation (fully-automatic).[25][7][26]
Another early example is the 1955Citroën DS, which used a 4-speed "BVH" transmission. This semi-automatic transmission used an automated clutch, which was actuated usinghydraulics. Gear selection also used hydraulics, however, the gear ratio needs to be manually selected by the driver. The 1956Renault Dauphine 3-speed manual transmission was available with an optionalFerlec automated clutch, which used an electromagnetically operated clutch system.[27][28] Other clutchless manual transmissions included the 1967NSU Ro 80 (3-speedFichtel & Sachs) and 1967Porsche 911 (4-speedSportomatic), both of which used vacuum-actuated clutches and hydraulic torque converters. The 1968Volkswagen Beetle andVolkswagen Karmann Ghia offered a 3-speedAutostick transmission, which used an electric switch on the gear shifter connected to asolenoid, to operate theelectro-pneumatic vacuum clutchservo.[29][30]
In 1963,Renault switched from the automated clutch to a fully-automatic 3-speed Jager transmission, which consisted of an electro-mechanical control unit that operated both the clutch and shifting, effectively making it one of the earliest automated manual transmissions.[31][32][33] The Jager transmission was controlled via dash-mounted electronic push-buttons.[34]
TheIsuzuNAVi5 5-speed automatic transmission was introduced in the 1984Isuzu Aska mid-size sedan (sold in the Japanese domestic market only). This transmission, originally designed for trucks, was based on a manual transmission with the addition ofhydraulic actuators for the gear shifter and the clutch. Initial versions did not allow direct selection of gear ratios, instead allowing drivers only to lock out higher gears (as per many traditional automatic transmissions). Later versions added a manual mode, allowing the driver to control the gear selection.
Several companies owned byFiat S.p.A. were influential in the development of automated manual transmissions.Ferrari's involvement with automated manual transmission began with the 7-speedsemi-automaticpaddle-shift transmission used in the 1989Ferrari 640 Formula One racing car. In 1992, theFerrari Mondial T introduced the option of a "Valeo" 5-speed semi-automatic transmission.[35] This transmission used an electro-mechanical actuator to automatically operate the clutch,[36] while the gearshift mechanism was a standard H-pattern shifter operated as per normal transmissions.[37] In 1997, theFerrari F355 became available with an "F1" 6-speed transmission, which uses paddle-shifters located behind the steering wheel or can be driven in a fully-automatic mode.[38] The F355's successors offered similar transmissions,[39] until the company switched to a dual-clutch transmission for the Ferrari 458 in 2009.
Sister companyAlfa Romeo introduced the relatedSelespeed 5-speed automatic transmission for theAlfa Romeo 156 in 1999.[40][41] This was followed by Maserati's 2001 introduction of the relatedCambiocorsa 6-speed automatic transmission in theMaserati Coupé.[42] Selespeed was also used in theFiat Punto andStilo models.
BMW's involvement with automated manual transmissions began in 1993, when the "Shift-tronic" 6-speed semi-automatic was offered on theAlpina B12 coupe (based on theE31 850CSi).[43][44] Using an automated clutch paired to a standard H-pattern shifter (as per the Ferrari Mondial T), the transmission was supplied by LuK and fitted to less than 40 cars.[45] Mass-production of automated manual transmissions began for BMW in 1997 with the introduction of the "SMG" 6-speed automatic transmission in theE36 M3 coupe.[46] Although the name "SMG" was an abbreviation of "Sequential Manual Gearbox", the transmission internal were as per a typical (synchromesh-equipped) manual transmission, not a truesequential manual transmission. The SMG was replaced by the SMG-II when theE46 M3 was introduced in 2000.[47] BMW's final AMT (before being replaced by a dual-clutch transmission) was the 7-speed SMG-III used in the 2004-2010BMW E60 M5 and relatedBMW E63 M6. The SMG-III could achieve a shift time of 65 milliseconds in its most aggressive mode[48]
From 2002 to 2007, thethird-generation Toyota MR2 was available with an "SMT" 6-speed automated manual transmission. The SMT system utilized an electro-hydraulic activation system for both the clutch and shifting, but no H-pattern shifter like with the standard transmission. Instead, there was a shift lever that could be pulled and pushed forward or backward to upshift and downshift, as well as the addition of electronic steering-wheel-mounted shift buttons.
Brands within theVolkswagen Group have typically useddual-clutch transmissions instead of automated manual transmissions, however a 6-speed "E-gear" automated manual transmission was introduced for the 2004Lamborghini Murciélago.[49] andLamborghini Gallardo.[50][51] The E-gear was used on the successors to the Murciélago and Gallardo, and it was also available on the 2007-2012Audi R8 (Type 42), marketed as the "R-tronic" transmission.[52][53][54]
| Automotive transmissions |
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| Manual |
| Automatic /Semi-automatic |
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