CVT Evolution Part 1 Seamless Driving and Improved … Pulley Transmission Mechanism for CVT CVT is...
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Transcript of CVT Evolution Part 1 Seamless Driving and Improved … Pulley Transmission Mechanism for CVT CVT is...
EnginePulley
Transmission Mechanism for CVTCVT is the mechanism that can deliver the power of the engine efficiently to the tires through pulleys, one for the engine (left) and one for the tires (right). The pulleys are set up between two plates. As the plates get closer or further away from each other, the diameter of the front and back pulley parts in contact with the belt changes. CVT shifts gears (transmission) through this change in diameter, in other words, by the transmission gear ratio changing.
Seamless Driving and Improved Fuel Efficiency!
CVT Evolution Part 1
Three types of automatic transmissionImagine you are riding a bicycle with gears.
When starting off or on a slope, you switch down to a low
gear and then it will be easier to pedal. But when your speed
increases or when you're going down a hill, you will get the
feeling that you are pedaling more than necessary if you stay
in the low gear.
So you go up a gear or two, and then you zip along.
Well, an automobile transmission is fundamentally the same
idea. In the same way that the strength of a human body has
limits, so too is it hard to greatly change the torque in an
engine. And that's where gears come in. By using the high
gears and low gears at different times, you can move
forward smoothly without needing to change the amount of
effort you put into pedaling – or, in case of a car, the amount
of power from the engine.
With a car, a driver selects a low gear (i.e. first or second)
when starting off from a traffic signal or going up a hill. And
then, as the car picks up speed, the drive will shift up to
fourth or fifth gear.
In Japan, over 90% of vehicles have automatic transmissions
(often called just “automatic” ) that can change gears by
itself. We can classify automatic transmission systems into
three main types. The first is the conventional automatic
transmission (AT). Then there is the dual clutch transmission
(DCT), and last but not least, continuously variable
transmission (CVT).
Of the three, CVT is uniqueTransmission, including the formerly mainstream manual
transmission, selects the combination of gears from many
types and then shifts gear. However, CVT sets the
transmission gear ratio freely with the pulley and the belt.
This is why CVT is known as “stepless” transmission.
How does it work? Okay, let's go back to your bicycle. Think about how you
switch gears on a bike? Changing gear changes the size
correlation (i.e. transmission gear ratio) of the front and back
wheels. Well, CVT uses a pulley and belt. As in the diagram
below, by changing the width of two pulleys it becomes
possible to change transmission gear ratio.
The advantage of CVT is that it can choose the optimum
transmission gear ratio. For example, there are times with AT
and DCT when the gear that is optimum for the vehicle's
speed is actually between fourth or fifth gear. The “gear” that
would really give the best driving results would be “4.25” or
“2.16,” but the number of gears is limited, so the system has
to compromise.
CVT doesn ' t have to compromise . I t 's a “stepless”
transmission where you can set the transmission gear ratio
freely, meaning the car can always drive in the gear ratio that
is most efficient. It can be used when driving at a set speed,
as well as for continuous optimal transmission gear ratio
during acceleration.
Due to this, fuel efficiency also improves. Another benefit is a
smooth ride without the jerk you can get from shifting gears.
CVT is transmission with great potential, achieving a powerful
driving experience that is smooth and with superb fuel
efficiency.
CVT Pulley MechanismAs the engine (input) pulley width increases and the tire (output) pulley width decreases, the engine pulley becomes smaller than the tire pulley for the diameter of the part where the pulley and belt are in contact. This is the state of being in low gear, such as first gear for AT. Vice versa, as the engine pulley width decreases and the tire pulley width increases, the diameter of the part where belt and pulley are in contact grows larger for the engine pulley than the tire pulley, which is the state of being in high gear (fifth or sixth for AT). One of CVT’ s fortes is that pulley width can be continuously changed, allowing the system to change transmission gear ratio smoothly and without steps.
High Speed
Tire Pulley
EnginePulley
EnginePulley
Tire Pulley
Low Speed
What is CVT? A subtle usage of pulleys and belt