Design Practices Passenger Car Automatic Transmissions
Introduction
Automatic transmissions are a common feature in passenger cars today. They offer a number of advantages over manual transmissions, including increased fuel economy, smoother shifting, and easier driving in stop-and-go traffic. However, automatic transmissions are also more complex and expensive to manufacture than manual transmissions.
The design of an automatic transmission is a complex process that involves a number of factors, including:
* The type of transmission (e.g., planetary gear set, torque converter, dual-clutch transmission)
* The number of gears
* The gear ratios
* The torque capacity
* The efficiency
* The weight
* The cost
Types of Automatic Transmissions
There are three main types of automatic transmissions used in passenger cars: planetary gear sets, torque converters, and dual-clutch transmissions.
Planetary gear sets are the most common type of automatic transmission. They use a set of planetary gears to change gears. Planetary gear sets are relatively simple to design and manufacture, and they are very efficient. However, they are also relatively heavy and expensive.
Torque converters are another common type of automatic transmission. They use a fluid coupling to transmit torque from the engine to the transmission. Torque converters are very smooth and quiet, and they can handle a lot of torque. However, they are also relatively inefficient and expensive.
Dual-clutch transmissions are a relatively new type of automatic transmission. They use two clutches to change gears. Dual-clutch transmissions are very efficient and fast, and they can handle a lot of torque. However, they are also relatively expensive and complex.
Number of Gears
The number of gears in an automatic transmission affects its fuel economy, performance, and drivability. A transmission with more gears can provide better fuel economy and performance, but it can also be more complex and expensive.
Most passenger cars have four or five gears. However, some cars have six or even seven gears. Cars with more gears typically have better fuel economy and performance, but they can also be more expensive.
Gear Ratios
The gear ratios in an automatic transmission determine how much the transmission changes the engine’s speed. The lower the gear ratio, the more the transmission changes the engine’s speed. This makes the car accelerate faster, but it also reduces the car’s top speed.
The higher the gear ratio, the less the transmission changes the engine’s speed. This makes the car accelerate more slowly, but it also increases the car’s top speed.
The gear ratios in an automatic transmission are typically chosen to provide a good balance between acceleration and fuel economy.
Torque Capacity
The torque capacity of an automatic transmission is the maximum amount of torque that the transmission can handle. The torque capacity of a transmission is determined by the strength of its components.
A transmission with a higher torque capacity can handle more torque without failing. This is important for cars with powerful engines that produce a lot of torque.
Efficiency
The efficiency of an automatic transmission is a measure of how much power is lost through the transmission. The efficiency of a transmission is determined by the design of the transmission and the materials used in its construction.
A more efficient transmission will lose less power and provide better fuel economy.
Weight
The weight of an automatic transmission is an important consideration for cars that are performance-oriented. A lighter transmission will reduce the car’s weight and improve its performance.
However, lighter transmissions are typically more expensive to manufacture.
Cost
The cost of an automatic transmission is a major factor to consider when choosing a car. Automatic transmissions are more expensive to manufacture than manual transmissions, and this cost is passed on to the consumer.
However, automatic transmissions can also provide a number of benefits over manual transmissions, such as increased fuel economy, smoother shifting, and easier driving in stop-and-go traffic. So, the cost of an automatic transmission should be weighed against the benefits it provides.
Conclusion
The design of an automatic transmission is a complex process that involves a number of factors. By carefully considering these factors, engineers can design transmissions that meet the specific needs of different vehicles.
Automatic transmissions are a valuable addition to many passenger cars. They offer a number of advantages over manual transmissions, including increased fuel economy, smoother shifting, and easier driving in stop-and-go traffic. However, automatic transmissions are also more complex and expensive to manufacture than manual transmissions.
