Semi-automatic transmission
The first usage of semi-automatic transmissions was in automobiles, increasing in popularity in the mid-1930s when they were offered by several American car manufacturers.
However, semi-automatics systems in newer motorcycles, racing cars, and other types of vehicles often use gear selection methods such as shift paddles near the steering wheel or triggers near the handlebars.
Fluid couplings (most commonly and formerly used in early automatic transmissions) have also been used by various manufacturers, usually alongside some form of mechanical friction clutch, to prevent the vehicle from stalling when coming to a standstill or at idle.
A typical semi-automatic transmission design may work by using Hall effect sensors or micro switches to detect the direction of the requested shift when the gear stick is used.
A clutchless manual system, named the Autostick, was a semi-automatic transmission introduced by Volkswagen for the 1968 model year.
The top of the gear stick was designed to depress and activate an electric switch, i.e. when touched by the driver's hand.
An AMT functions in the same way as older semi-automatic and clutchless manual transmissions, but with two exceptions; it is able to both operate the clutch and shift automatically, and does not use a torque converter.
Their biggest disadvantage is poor shifting comfort due to the mechanical clutch being disengaged by the TCU, which is easily noticeable as "jolting".
[citation needed] Some transmission makers have tried solving this issue by using oversized synchronizer rings and not fully opening the clutch during shifting—which works in theory, but as of 2007, there have not been any series production cars with such functions.
[needs update] In passenger cars, modern AMTs generally have six speeds (though some have seven) and a rather long gearing.
The AMT can be switched to a clutchless manual mode wherein one can upshift or downshift using a console-mounted shift selector or paddle shifters.
In 1901, Amédée Bollée developed a method of shifting gears that did not require the use of a clutch and was activated by a ring mounted within the steering wheel.
Prior to the arrival of the first mass-produced hydraulic automatic transmission (the General Motors Hydra-Matic) in 1940, several American manufacturers offered various devices to reduce the amount of clutch or shifting input required.
[37] These devices were intended to reduce the difficulty of operating the unsynchronised manual transmissions, or "crash gearboxes", that were commonly used, especially in stop-start driving.
[38] It used a planetary gearset with a clutch pedal for starting from a standstill and switching between the "low" and "high" ranges.
The system could control the throttle cable (to keep the engine at the required RPM for the gear change) and vary the rate of clutch engagement.
A similar product was the German Saxomat automatic clutch system, which was introduced in the mid-1950s and available on various European cars.
This allowed clutchless shifting with a single column-mounted selector, while the driver simultaneously lifted off the accelerator to change gear.
[61] Compared to fully automatic transmissions of the time, the E-Stick offered the fuel economy of a stick-shift, with vacuum and electric switches controlling the clutch.
The E-Stick three-speed transmission was offered on the larger Rambler Classic models, along with an overdrive unit.
The automatic mechanical clutch allowed the car to accelerate from a stop, whereas the torque converter enabled it to do so in any gear.
Dampening engine vibrations and providing torque multiplication, it functioned as a sort of "reduction gearbox", so the actual mechanical gearbox only needed three forward gears (this is why conventional automatic transmissions with torque converters normally have fewer gears than manual transmissions).
The Torque-Drive was essentially a 2-speed Powerglide automatic transmission without the vacuum modulator, requiring the driver to manually shift gears between "Low" and "High".
[115] The car won its debut race at the Brazilian Grand Prix, but for much of the season suffered from reliability problems.
Pre-programmed, computer-controlled, fully-automatic upshifts and downshifts were re-introduced and allowed from 2001, and were permitted from that year's Spanish Grand Prix, but were banned again in 2004.
DTM currently uses a Hewland DTT-200 6-speed sequential transmission with steering-wheel-mounted shift paddles, which was introduced for the 2012 season with the new rule change.
