Automotive market is replete with technologies of all kind. The CVT transmission is one among them and has become really popular choice among manufacturers. In fact it is considered as the best transmission. Why is that? In this article we answer a few common questions about CVT (Continuously Variable Transmission) and discuss its limitations.
What are the major components of a CVT transmission?
A CVT transmission has two conical pulleys (that can vary in diameter) and a steel belt which essentially make up the basic CVT transmission. A planetary gear set arrangement is generally present to reverse the motion and achieve a reverse gear. A differential is present as in case of all other cars to split the power between wheels.
How does a CVT achieve different gears and how is it different from others?
In most other transmissions the gear ratios are achieved by meshing of different gears present on the output and input shafts. However, in case of a CVT there aren’t any gears and the torque variation is achieved by varying the size of input and output pulleys. In case of DSG, Manual and AMT, gear ratios are achieved by different gear sets and since there are a limited number of sets, it’s a stepped transmission.
Why is CVT known as a step-less transmission?
In case of CVT, the input shaft can be maintained at constant angular velocity and the range of effective gear ratios can be achieved smoothly by varying the diameter of pulleys. Due to this seamless change of ratios that they can achieve, the CVTs are known as step-less transmission.
How is a reverse gear achieved in CVT?
A reverse gear is achieved by the use of a planetary gear set arrangement. The input shaft carries the Sun while two row carrier set is connected to the input pulleys. The forward motion is achieved by connecting the ring and sun gear with a clutch pack, which makes all gears (including planets) rotate at equal angular speed and in one direction. Another clutch pack is used to keep the ring gear stationary and this forces the sun gear to drive the planet carrier in the opposite direction. Since the carrier set is connected to the input pulley, it also drives in the opposite direction, and that’s how the reverse gear is achieved.
What is the limitation of CVT gearbox?
The CVT is really efficient, however its weakest part is the belt that connects the input and output shafts. Due to this weak part, the transmission’s torque carrying capacity is not really great as compared to some of the other transmission. Therefore, it’s application is limited to only petrol engines or moderately powerful engines that do not have very high torque.