The following are the key takeaways from this article:
- Transmission is important for delivering power to the wheels.
- The conventional automatic transmission works on the hydraulic principle and comprises of oil pump, sensors, and transmission band.
- Automatic transmission pros include easier driving, greater torque, and power distribution.
- But there are many cons, including low fuel mileage and higher maintenance costs.
- The manual transmission comprises gear shafts, a doggy clutch, and a synchromesh.
- Pros of manual transmission include greater control over the vehicle and good fuel mileage.
- The cons of manual transmission include tiresome experience in traffic and rolling back in harsh conditions.
- CVT is a form of automatic transmission that comprise belts, pulleys, and shafts controlled by sensors.
- The advantage of CVT has increased fuel mileage and greater power supply.
- The cons of CVT include expensive maintenance and the requirement of special fluids.
- The dual-clutch transmission is a hybrid between an automatic and manual transmission that works with several clutches.
- The pros of dual-clutch transmission are increased fuel mileage and efficiency.
- The cons of dual-clutch transmission include complex design and periodic fluid change.
Transmission is essential for delivering engine power to the vehicle. However, there needs to be more awareness regarding the types of transmission among the common public. They recognize transmission as only of two types that are automatic and manual transmission. It is to be noted that conventional automatic transmission has had several problems, so automotive makers have come up with other forms of transmission. This article discusses major transmission types, their design specifications, working, and pros and cons.
Common Types of Transmission
Following are a few common types of transmissions used in vehicles:
You might have seen cars with no clutch pedal. In these cars, drivers are not required to put input to change the gears. Such transmission is called an automatic transmission, in which the gears are changed automatically (2). Modern vehicles having CVT (constantly varying transmission), DCT (dual-clutch transmission), etc., are advanced automatic transmission forms.
Design of Automatic Transmission
The automatic hydraulic transmission comprises an oil pan and an oil pump. The oil pump is further connected to a transmission speed sensor sending signals to it for pumping of different fluid levels in the transmission. As the engine revs up or revs down, the transmission sensor sends a signal so the pump creates optimum pressure for the fluid to travel in the desired band and obtain desired gear ratio (2). The oil pump is typically mounted between planetary gears and the torque converter. Coming onto the torque converter is another essential component of the automatic transmission, as its function is similar to the clutch in the manual transmission system. In addition, a torque converter creates coupling and decoupling effects in the engine during a gear shift.
Working and Function of Automatic Transmission
When the engine revs up to a certain RPM and requires a gear shift, the speed sensor sends a signal to the oil pump that sends a signal to the right transmission band. The torque converter decouples, and the gear is shifted. Different modes of automatic transmission include N (neutral), P (parking), D (drive), R (reverse), etc. (2). Some modern models also have the option of L (lower mode) to assist drivers in severe conditions. So, you have to put the car in D for driving, and the torque converter, speed sensor, and oil pump do the rest. When parking the car, put the car in parking mode to disengage the gears.
Pros of Automatic Transmission
By replacing traditional gears with planetary gear, the power distribution is much greater over a large area. So, automatic vehicles are more powerful than manual ones. Similarly, automatic transmission creates greater torque (1). The torque converter replaces the conventional clutch so that the vehicle will speed up even in idle mode, and the power is much greater than the manual vehicle.
Cons of Automatic Transmission
The cons of automatic transmission include higher maintenance costs, lower fuel averages, and less control over the vehicle. In addition, as discussed above, the automatic transmission is driven through fluid pressure, so you have to replace gear fluid and filter much more often than other transmission types.
A manual gear stick or standard transmission is the type of transmission in which the drivers are supposed to change the gear.
Design of Manual Transmission
The manual transmission design is usually simpler than an automatic transmission. It comprises different shafts with gears and other components attached to them (1). In normal passenger vehicles, there are three shafts: an input shaft, an output shaft, and a countershaft. Dog clutch/dog mesh is another important component of manual transmission that helps maintain the right gear ratio. Whenever a particular gear is engaged, the dog mesh of that gear is engaged, locking that gear and preventing gear slippage. Synchromesh is another important component of manual transmission that alleviates manual engine rev-matching with each gearshift. The final and most important component of a manual transmission is the clutch that couples and decouples the engine during gearshift.
Working and Function of Manual Transmission
The input shaft is directly meshed with the engine and rotates at the same speed as the engine. On the other hand, the input shaft also meshes with the gears on the countershaft. The output shaft also meshes with the countershaft. However, the output shaft rotates on its own with the help of bearings (5). So, when the engine speed increases, the input shaft rotates at a greater speed, and the driver engages the clutch to shift gears. The mesh with the counter gear changes, and the counter gear changes the mesh with the output shaft.
Pros of Manual Transmission
Further, manual transmission vehicles also cost less than automatic transmission vehicles. Further, you control your vehicle, so better fuel mileage is expected of your manual vehicle, given that all components are functioning properly (1). Finally, driving a manual transmission will be fun, especially if you are a classic driver.
Cons of Manual Transmission
For some drivers, the con will be gear shift, especially if they are new and inexperienced. As discussed above, the clutch must be pressed at the right time to avoid engine stalling. That is where inexperienced drivers need help to drive the vehicle. Further, manually shifting gears during a traffic jam would be hectic (2).
Constantly Varying Transmission
As discussed above, the automatic transmission has a con of low fuel average. It is because of varying engine RPM with varying speeds.
Design of CVT
Starting the CVT clutch is quite different from the manual transmission clutch. A CVT has a primary and secondary clutch. The primary clutch is a centrifugal clutch mounted on the engine shaft’s output end. This clutch allows the engine to rev without transmitting power to the wheels. The secondary clutch is mounted with the input shaft of the engine. It works to provide a torque sensation and enslaved person the primary clutch (5). There are four pulleys in CVT: fixed input pulley, fixed output pulley, feeding input pulley, and feeding output pulley.
Further, two shafts are input and output shafts, designed in CVT. The input shaft receives power from the engine and delivers it to the wheels via the output shaft. Finally, a V-belt delivers power between the input and output pulley.
Working of CVT
Sensors and microprocessors also function to actuate the hydraulic cylinder and deliver seamless gearshift without varying engine RPM. During engine functioning, the pulley distance also changes via belt movement (2). So, different components facilitate the working of CVT, achieving optimum gear ratio.
Pros of CVT
Another pro of CVT is that it can adapt to different road conditions by managing the power demand. Finally, when the engine RPMs are managed better, the emission rate is reduced compared to other forms of transmission (4).
Cons of CVT
For some drivers, driving with CVT can be boring as there is no feeling of gear shift, and the drivers might not feel the car accelerating. Further, its maintenance can be particularly expensive (3). The sensors of CVT can be damaged due to constant functioning or electric problems. These sensors can be expensive to repair/replace. The same is the case with other CVT components.
This is a type of automatic transmission that uses two sets of clutch for odd and even gears.
Design of Dual-Clutch Transmission
The design of a dual-clutch transmission is amended in a manual transmission. A clutch manages an even number of gears, while another manages an odd number. So, the gears can pre-select the gears making DCT shift gears several times faster than the manual transmission (3). Another difference in design is using a clutch pack instead of the torque converter. The clutch can be either a wet clutch or a dry clutch. The design of dual-clutch transmission also differs in terms of the clutch arrangement. Most commonly, two concentric clutches are located on the same axis. These clutches are attached to the flywheel, where the diameter of the outer clutch is generally greater than the inner clutch. At the same time, another design is two similar-sized clutches located side-by-side. Two side-by-side input shafts originating from the input shaft drive the dual-clutch system.
Working and Functioning of Dual-Clutch Transmission
The first thing a driver needs to know is that all clutches in dual-clutch transmission are computer controlled, so there is no need for a clutch pedal (4). It can also be called a hybrid of an automatic and manual transmission. Both clutches function similarly to the manual transmission to disengage the engine from the driveline for smooth changing of gears.
Pros of Dual-Clutch Transmission
Hence, it improves acceleration, making it an automatic choice for supercars (3). In addition, the clutch is operated via computer instead of the foot pedal. So, the gear shift is particularly smoother. Some models also allow drivers to operate the clutch themselves, enhancing the driver’s experience. Finally, the dual-clutch transmission allows for improved fuel efficiency and other options.
Cons of Dual-Clutch Transmission
Furthermore, you are also required to change the fluid of dual-clutch transmission periodically, and the cost of fluid replacement can be generally high.