Since quite some time, there have been various types of gearboxes used in cars, from basic chains with gears to the torque converters that are found in the majority of vehicles on the road today. Although their purpose has not changed over time, gearboxes have undergone a number of application-specific changes.
In a car with an automatic transmission, a torque converter is a device that transfers the engine’s motive power to the transmission. The torque converter plays the following crucial responsibilities that help improve fuel efficiency and driving performance.
- The Transfer of Torque: It transfers engine torque to the transmission smoothly.
- Increase in Engine Torque: It amplifies and transmits engine torque to the transmission when a lot of torque is needed during startup or acceleration.
- Vibration Reduction: It enhances interior silence by attenuating vibrations caused by the engine through the use of a damper. (When coupled directly and the lock-up clutch is engaged).
Transmission with two clutches
The Dual Clutch Transmission (DCT) helps with gear shifts by working with two clutches in tandem. The concept of a DCT was first proposed in France in the early 1930s, but it was never widely adopted at that time. However, Porsche developed the Porsche Doppelkupplungsgetriebe (PDK) in the 1980s, and like other inventions in the automobile industry, it was inspired by the needs of racing. In 1986, the Porsche 962 and PDK had success at Monza.
The PDK, however, did not persist for very long since the dry clutches on the market at the time did not offer the “smoothness” Porsche required to utilise the PDK on the road. Porsche subsequently started working on its own wet clutches, but that wasn’t a practical choice either. In 2009, as interest in DCTs developed globally, Porsche and ZF created the PDK 1 in collaboration with ZF. Due to the dual-clutches’ constant selection of the next gear and readiness to shift, DCTs, like the PDK, offer almost quick shifts. Most modern supercars have these incredibly fast gearboxes. However, they are unable to pick more than one gear at once and exhibit some intransigence when doing so.
The LST by Koenigsegg
Imagine a transmission that could shift gears at the DCT’s lightning-fast rate without being limited to only the adjacent gears. The Light Speed gearbox is a ground-breaking transmission created by Swedish manufacturer Koenigsegg that includes precisely that. There are seven clutches (yes, seven!) in the 9-speed gearbox. The transaxle includes the differential as well, and the entire assembly, including fluids, weighs under 90 kg. The 1600 horsepower Koenigsegg Jesko uses this transmission. The LST lacks selector forks, collars, or synchronizers to engage each specific gear, as contrast to a dual-clutch. Instead, nothing but opening and shutting clutches is used to carry out the selection. These clutches have a two-millisecond opening and closing time.
The LST’s multi-clutch setup allows it to change gears while simultaneously opening and closing each clutch, providing what Koenigsegg refers it as “ultimate power on demand,” or UPOD. With its flat-plane V8 and quick gear changes (literally), the Jesko is one of the few vehicles in the world capable of exceeding 300 MPH. Open-clutches are the best option for high torque and power applications, even though they might not find their way into typical road automobiles due to their inefficiency.
How it works?
The LST includes eight hydraulic clutches, including one for the limited-slip differential and one each for the reverse and forward gearsets (not shown). Two clutches engage the output shaft and countershaft (the middle shaft in the drawings) to propel the vehicle forward (the bottom one). The engine to differential torque path is depicted by the red lines. Slipping the clutch is required to accelerate from a stop.