This article clearly explains how automatic transmission works with a simple animation. Some technologies are easier to understand with the help of 3D animation. However, what about the 6-speed automatic transmission from Allison. To visualize and understand this beautiful planetary gear set mechanism a 2D animation is ideal. You can consider this 2D drawing as a cross-section of the 3D model. A planetary gear set has 2 inputs and 1 output. If you correctly understand working of a planetary gear set.
How automatic transmission works
You can easily understand how automatic transmissions works from the 2D animation. The essence of the planetary gear set is that just by giving different speeds to the ring and sun gears you will be able to get different speeds at the output. Let’s see it in the 2D animation. In an automatic transmission the input and the output are not directly connected.
As shown an intermediate shaft connects them. Now a small suggestion before you proceed.You will be able to explain all seven gears by yourself by pausing the video for a moment for understanding the mechanism.
If you press the clutch, the input will be connected to the sun gear. If you press clutch C5, the output gear will be stationary. Now as shown in the video let’s add one more gear set, here comes the tricky part. The carrier of this set is connected to the ring gear of the first set. This means that the output of the second set is connected to the input of the first set. Think for a moment about what happens when you apply C1 and C4. Since C4 is applied, the ring gear of the second set will be stationary.
This makes the carrier turn. This carrier connects to the ring gear of the first set. So the ring gear of the first set will also turn. This, in turn, increases the output speed or we will get the second gear to obtain the fourth gear.
It also uses a direct drive, a rotating clutch module. We know that for a direct drive both the sun and the ring gear should rotate at the input speed. If we press C2 and C1 together, this is what happens in the very same mechanism. If you apply C2 and C4, you will get very high speed at the output.
How gears engage and disengage.
Think for a moment and try to understand. This is clear that the carrier of the second set will turn at the input speed however here the ring gear is stationary. This makes the sun gear turn at almost three times the speed of the input. Eventually, it obtains a very high out put speed. Its uses one more gear set to obtain the remaining gear ratios. However, the sun gear of this set does not connect to the shaft instead it connects to the rotating clutch module. So this sun gear will always turn at the input speed. Here again, the output of the set connects to the input of the adjacent set. Applying C3 gives the remaining gear ratios. This means that the brown carrier or ring gear of the second set will turn at one-third of the input speed for the remaining cases.
For the third gear apply to see one as well for the fifth gear apply C2 along with C3. The reverse is an interesting mechanism here. C5 applied along with C3 so here the carrier of the second set is stationary. This means that the planet gears of this set will not be able to revolve. That they will simply spin. This spin is in the same direction as the input. This planetary spin will make the corresponding sun gear spin in the opposite direction. As a result, the output sun gear will also turn in the opposite direction. Thus we will get the reverse gear.
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