Except for direct drive electric systems, all engines require some type of transmission to connect the prime mover (engine) and the wheels of the vehicle. Due to the engine in question’s features, a necessity is created.
The engine would give good efficiency when run in a certain speed range, which may differ from the speed range where the engine can produce the most power. Engines may only produce respectable torque when they rotate between a specific range of engine speeds.
There must be some sort of device to connect what the engine can produce and what the vehicle wants depending on the load and speed of the vehicle.
For the sake of time, we’ll leave the issue of EV transmissions for another time and stick to the internal combustion engines (ICEs). Having said that, ICE transmissions perform the following tasks:
- ICEs are unable to produce torque at idle. The vehicle’s stationary wheels must therefore be able to connect with the engine, which is already rotating at idle or a little higher engine speed, using the transmission.
- Only within a narrow engine speed range do ICEs produce usable torque and acceptable efficiency. This speed range will make up a fraction of the engine’s total operating range. The engine’s production of power, which is inversely proportional to both torque and engine speed, would first rise with speed, peak, and then fall (or run flat) with an increase in engine speed. A transmission mounted in a vehicle between the engine and the wheels would need to give what the engine is capable of and what the driver demands within the limits of the vehicle’s operational range.
Conventional Automatic (CA), Continuously Variable Transmission (CVT), Dual Clutch Automatic (DCA or DCT), and Automated Manual Transmission (AMT) are the 4 types of automatic transmissions that are available in the market.
1. Conventional Automatic
The conventional automatic transmission was the first to be utilized in mass-market cars and is the most popular automatic transmission in the world. It was the first automobile to use a torque converter to create a smooth shift shock and an electronic computer to change gears.
All of the gears in the transmission’s epicyclic gear train were in mesh, and the gears could be changed using hydraulic piston-cylinder configurations and selector-valve settings. There were just two clutch and brake locations in early automobiles.
A centrifugal governor attached to the wheels was used to shift gears by opposing the force acting on the hydraulic valve. This configuration permitted downshifts when the accelerator was slammed while in a higher gear as well as shifts at faster engine and vehicle speeds.
2. Continuously Variable Transmission
Stepped gear ratios are provided by transmission technologies to preserve engine performance, although adding more ratios can increase expense and complexity. With continuously variable transmissions (CTTs), there is no upper limit on the number of ratios that can be used.
Consumer automobiles frequently have pulley- and belt/chain-based CVTs, which achieve infinite ratios by securing a belt/chain between two pulleys of different diameters.
Centrifugal forces and springs may not be sufficient for pulley movement, however, because modern automotive CVTs may not be sophisticated enough for stringent requirements.
3. Dual Clutch Automatic
The Dual Clutch Transmission (DCT) was created for Formula 1 teams to offer a speedy and lightweight transmission. There are two clutches on each of the two manual transmissions, one with odd gears and the other with even gears. The odd gear clutch transfers power from the engine to the wheels while keeping the even clutch open.
4. Automated Manual Transmission
AMTs are manual transmissions with actuators for clutch actuation and gear change that are managed by the electronic brains of the TCU. Since they are often add-on components, manufacturers may share parts more effectively, lowering the cost of vehicles with AMTs.
Conclusion
Although manufacturers offer alternatives based on price, fuel efficiency, and car size, automatic transmission systems seek to be convenient and cost-effective. To learn more about it check out transmission transportation cases – Endural.