The automated manual transmission (AMT) is a type of transmission for motor vehicles. It is essentially a conventional manual transmission [1] [2] [3] [4] [5] equipped with automatic actuation to operate the clutch and/or shift gears.
Many early versions of these transmissions that are semi-automatic in operation, such as Autostick , which automatically control only the clutch – often using various forms of clutch actuation, such as electro-mechanical, hydraulic, pneumatic, or vacuum 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 as clutchless manual systems. [8] Modern versions of these systems that are fully automatic in operation, such as Selespeed and Easytronic , can control both the clutch operation and the gear shifts automatically, by means of an ECU, 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 widespread dual-clutch transmission, but remained popular for smaller cars in Europe and some developing markets, particularly India, where it is notably favored over conventional automatic and CVT transmissions due to its lower cost. [11]
Automated manual transmissions can be semi-automatic or fully-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 or electro-hydraulic actuation, [12] electro-mechanical, [13] pneumatic, [6] [14] [15] electromagnetic, [16] [17] [18] or even purely electrical using an electric 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 the transmission shift lever, while electronic sensors and actuators connected to a TCU (transmission computer) or microprocessor 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 a servo-controlled unit, connected to various actuators, a solenoid and sensors which control the clutch automatically.
Another alternate means of clutch automation is the "clutch-by-wire" system. The system generally uses an electric actuator and electronic 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 conventional automatic transmission), while traditional semi-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 a manumatic, the latter of which is an automatic transmission (automatics use a torque 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), or electro-mechanical (less expensive, but usually limited to 250 N·m (184.5 lb-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 just electric 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 Suzuki Auto Gear Shift and Dacia/Renault Easy-R , usually operate in conjunction with electronic throttle control to initiate gear shifts based on certain RPM and/or throttle position.
The automated manual transmission has its origins in early clutchless manual transmissions that began to appear on mass-production cars in the 1940s and 1950s. An early example of this transmission was introduced with the Hudson Commodore in 1942, called Drive-Master. This unit was an early semi-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 1955 Citroën DS, which used a 4-speed "BVH" transmission. This semi-automatic transmission used an automated clutch, which was actuated using hydraulics. Gear selection also used hydraulics, however, the gear ratio needs to be manually selected by the driver. The 1956 Renault Dauphine 3-speed manual transmission was available with an optional Ferlec automated clutch, which used an electromagnetically-operated clutch system. [27] [28] Other clutchless manual transmissions included the 1967 NSU Ro 80 (3-speed Fichtel & Sachs) and 1967 Porsche 911 (4-speed Sportomatic), both of which used vacuum-actuated clutches and hydraulic torque converters. The 1968 Volkswagen Beetle and Volkswagen Karmann Ghia offered a 3-speed Autostick transmission, which used an electric switch on the gear shifter connected to a solenoid, to operate the electro-pneumatic vacuum clutch servo. [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]
The Isuzu NAVi5 5-speed automatic transmission was introduced in the 1984 Isuzu 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 of hydraulic 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 by Fiat S.p.A. were influential in the development of automated manual transmissions. Ferrari's involvement with automated manual transmission began with the 7-speed semi-automatic paddle-shift transmission used in the 1989 Ferrari 640 Formula One racing car. In 1992, the Ferrari 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, the Ferrari 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 company Alfa Romeo introduced the related Selespeed 5-speed automatic transmission for the Alfa Romeo 156 in 1999. [40] [41] This was followed by Maserati's 2001 introduction of the related Cambiocorsa 6-speed automatic transmission in the Maserati Coupé. [42] Selespeed was also used in the Fiat Punto and Stilo models.
BMW's involvement with automated manual transmissions began in 1993, when the "Shift-tronic" 6-speed semi-automatic was offered on the Alpina B12 coupe (based on the E31 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 the BMW E36 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 true sequential manual transmission. The SMG was replaced by the SMG-II when the E46 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 2004-2010 BMW E60 M5 and related BMW E63 M6. The SMG-III could achieve a shift time of 65 milliseconds in its most aggressive mode [48]
From 2002 to 2007, the Toyota MR2 (3rd generation) 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 the Volkswagen Group have typically used dual-clutch transmissions instead of automated manual transmissions, however a 6-speed "E-gear" automated manual transmission was introduced for the 2004 Lamborghini Murciélago. [49] and Lamborghini Gallardo. [50] [51] The E-gear was used on the successors to the Murciélago and Gallardo, and it was also available on the 2007-2012 Audi R8 (Type 42), marketed as the "R-tronic" transmission. [52] [53] [54]
Automotive transmissions |
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An automatic transmission is a multi-speed transmission used in motor vehicles that does not require any input from the driver to change forward gears under normal driving conditions. Vehicles with internal combustion engines, unlike electric vehicles, require the engine to operate in a narrow range of rates of rotation, requiring a gearbox, operated manually or automatically, to drive the wheels over a wide range of speeds.
A transmission is a mechanical device which uses gears to change the speed or direction of rotation in a machine. Many transmissions have multiple gear ratios, but there are also transmissions that use a single fixed gear ratio.
A manual transmission (MT), also known as manual gearbox, standard transmission, or stick shift, is a multi-speed motor vehicle transmission system, where gear changes require the driver to manually select the gears by operating a gear stick and clutch.
A semi-automatic transmission is a multiple-speed transmission where part of its operation is automated, but the driver's input is still required to launch the vehicle from a standstill and to manually change gears. Semi-automatic transmissions were almost exclusively used in motorcycles and are based on conventional manual transmissions or sequential manual transmissions, but use an automatic clutch system. But some semi-automatic transmissions have also been based on standard hydraulic automatic transmissions with torque converters and planetary gearsets.
Getrag, stylized as GETRAG, was a major supplier of transmission systems for passenger cars and commercial vehicles. The company was founded on 1 May 1935, in Ludwigsburg, Germany, by Hermann Hagenmeyer; as the Getriebe und Zahnradfabrik Hermann Hagenmeyer GmbH & Cie KG.
A preselector gearbox is a type of manual transmission mostly used on passenger cars and racing cars in the 1930s, in buses from 1940-1960 and in armoured vehicles from the 1930s to the 1970s. The defining characteristic of a preselector gearbox is that the gear shift lever allowed the driver to "pre-select" the next gear, usually with the transmission remaining in the current gear until the driver pressed the "gear change pedal" at the desired time.
A transmission control unit (TCU), also known as a transmission control module (TCM), or a gearbox control unit (GCU), is a type of automotive ECU that is used to control electronic automatic transmissions. Similar systems are used in conjunction with various semi-automatic transmissions, purely for clutch automation and actuation. A TCU in a modern automatic transmission generally uses sensors from the vehicle, as well as data provided by the engine control unit (ECU), to calculate how and when to change gears in the vehicle for optimum performance, fuel economy and shift quality.
A gear stick, gear lever, gearshift or shifter, more formally known as a transmission lever, is a metal lever attached to the transmission of an automobile. The term gear stick mostly refers to the shift lever of a manual transmission, while in an automatic transmission, a similar lever is known as a gear selector. A gear stick will normally be used to change gear whilst depressing the clutch pedal with the left foot to disengage the engine from the drivetrain and wheels. Automatic transmission vehicles, including hydraulic automatic transmissions, automated manual and older semi-automatic transmissions, like VW Autostick, and those with continuously variable transmissions, do not require a physical clutch pedal.
Shift time refers to the time interval between gear changes in a transmission. This interval is the time in which power delivery is transferred to the next selected gear, and engine speed is reduced or increased to synchronize the speed of the next gear. Shift time is usually in reference to motor vehicles, but can apply to any gearbox.
A sequential manual transmission, also known as a sequential gearbox, or a sequential transmission, is a type of non-synchronous manual transmission used mostly for motorcycles and racing cars. It produces faster shift times than traditional synchronized manual transmissions, and restricts the driver to selecting either the next or previous gear, in a successive order.
Selespeed is the name of an automated manual transmission used in Alfa Romeo cars, developed by Italian company Magneti Marelli and made by Graziano Trasmissioni.
A non-synchronous transmission, also called a crash gearbox, is a form of manual transmission based on gears that do not use synchronizing mechanisms. They require the driver to manually synchronize the transmission's input speed and output speed.
Twin Clutch SST is the brand name of a six-speed dual-clutch automatic transmission, developed by Getrag for Mitsubishi Motors. The system was first incorporated in the 2008 Lancer Evolution X, and was designed to be a more performance-oriented system than that developed by rival manufacturers, with shorter gear ratios optimized for acceleration.
A MultiMode manual transmission is a type of automated manual transmission offered by Toyota. It uses a traditional manual gearbox with a computer-controlled clutch actuated by permanent magnet motors. Multimode Manual Transmission is available in the Aygo, Yaris, Corolla, Corolla Verso, Mark X and Auris in Europe, and should not be confused with Multimode Automatic Transmission, which is offered in the North American market by Toyota.
A dual-clutch transmission (DCT) is a type of multi-speed vehicle transmission system, that uses two separate clutches for odd and even gear sets. The design is often similar to two separate manual transmissions with their respective clutches contained within one housing, and working as one unit. In car and truck applications, the DCT functions as an automatic transmission, requiring no driver input to change gears.
A motorcycle transmission is a transmission created specifically for motorcycle applications. They may also be found in use on other light vehicles such as motor tricycles and quadbikes, go-karts, offroad buggies, auto rickshaws, mowers, and other utility vehicles, microcars, and even some superlight racing cars.
Car controls are the components in automobiles and other powered road vehicles, such as trucks and buses, used for driving and parking.
The Dacia Easy-R is an automated manual transmission used by Renault and Dacia that uses electro-mechanical actuation to automate the gear shifts. The Easy-R uses a traditional manual gearbox with a computer-controlled, electronic clutch; the gear shifts are automatic, and the need for a clutch pedal is eliminated. The number of parts has been reduced by a quarter, ensuring better reliability and simplified maintenance.
Earl Avery Thompson was an American engineer and inventor who had a goal to make driving the automobile safer by reducing the effort required to shift the manual transmission of the day. Thompson even wanted to automate the process of shifting the transmission. Two of his most notable achievements towards that goal are listed on this page:
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