Welcome back! We’re still on our journey learning about Transmissions – in particular, the Automatic Transmission. As always before we lift the hood, let’s do a quick recap & review some definitions.
Previously on Anthony’s Automotive Blog….
Last week, we talked about automatic transmissions. If you wish to do a quick re-read of it, you can find it here. For the quick recap, keep going.
The Planetary Gear System is what drives the Automatic Transmission vehicle. This system consists of the Ring Gear, the Sun Gear and the Planetary Gears (one or more) that rotate in between the first two. It is the combination of the locking and unlocking of one or more of these gears that allows the car to shift gears.
Now, let’s add the Clutch Pack and Band to this Gear System and really get moving. But first, let’s make sure you understand the lingo that we use.
Our Growing Automotive Vocabulary
Here is a recap of some of the automotive words we listed last week just in case there is any lingering confusion. There are a couple of new additions as well.
Transmission – The mechanism by which power is transmitted from an engine to the wheels of a motor vehicle.
Torque Converter – A device that transmits or multiplies torque generated by an engine.
Gear – One of a set of toothed wheels that work together to alter the relation between the speed of a driving mechanism (such as the engine of a vehicle or the crank of a bicycle) and the speed of the driven parts (the wheels).
Automatic – A device or process that works by itself with little or no direct human control.
Automatic Transmission – An automotive transmission that can automatically change gears as the vehicle moves, freeing the driver from having to shift gears manually.
Clutch – A mechanism for connecting and disconnecting a vehicle engine from its transmission system.
Band – Something that binds, ties together, restrains, etc.; a strip or ring of wood, metal, rubber, etc. fastened around something to bind or tie it together.
Planetary Gear System – A gear system that consists of one or more planet gears (the gears in the middle area) that rotate or revolve around a sun gear (the gear in the center) and a ring gear (the gear on the outer edge).
Hydraulic – Operated by the movement and force of liquid; specifically, operated by the pressure created when a liquid is forced through an aperture, tube, etc..
Input – The act of putting in; or, what is put in
Output – The work done or amount produced by a person, machine, production line, manufacturing plant, etc., especially over a given period.
Shaft – A long, slender part or object.
Pack – A number of similar or related person or things.
Spline – A flat key or strip that fits into a groove or slot between parts.
Piston – A disk or short cylinder closely fitted in a hollow cylinder and moved back and forth by the pressure of a fluid so as to transmit reciprocating motion to the piston rod attached to it, or moved by the rod so as to exert pressure on the fluid.
The Planetary Gear System continued….
Last week I had included a Side View image of the Planetary Gear System. Let me include it again and quickly give thanks to the people at www.carparts.com for this image. It is the simplest image that I could find for this lovely and complicated system on the great wide web.
You can see the Input Shaft that is connected to the Ring Gear, as well as the Output Shaft that is connected to the Planetary Gears. What I want you to notice is that the Planetary Gears are also connected with the Clutch Pack. This is at the top and bottom of the image. The drum which houses the entire Clutch Pack is connected to the Sun Gear. So you have two parts of the Clutch Pack connected to two of the different gears.
On the outside of this whole unit, is the Band. The purpose of the Band is to tighten (and loosen) around the drum. This is another way to be able to lock the Sun Gear in place. When the Band is tightened, the Sun Gear cannot move. Or, with the assistance of the Clutch Pack, the Band, while tightened, will make the Sun Gear move in conjunction with the Planetary Gears.
Exactly what IS the Clutch Pack
I’m glad you asked that. The clutch pack consists of a drum and a bunch of disks. Now, these disks consist of two different types that are alternated as they are put in the drum. One half of these disks have splines on the outside of the disk that are designed to fit along groves that are on the inside of the drum. The other have splines on the inside of the disk that fit in the groves that are in the joining center part of the drum. In this Clutch Pack, there is a piston that, when activated by oil pressure, squeezes the disks together so they all turn as one. Which, in turn, will turn with whatever gears needed to shift the car into a different gear.
Ideas for Next Week
We’ve talked about the Planetary Gear System and all its parts and pieces. We have now added the new layers to this of the Clutch Pack and the Band that wraps around the outside. So, I think it is time for us to go back to where we started this whole journey and revisit Torque Conversion. You now understand the parts involved in this. So, next week, let’s really get into the nitty gritty of Torque Conversion.
I had a question last week of “where do I get my definitions?” Good ole…..
Until Next Time….