Automatic gearboxes are marvels of engineering, allowing vehicles to shift gears seamlessly without driver intervention. Understanding Automatic Gearbox How It Works involves delving into the crucial roles of bands and clutches. These components, working in harmony, are fundamental to achieving different gear ratios and smooth transitions. Let’s explore how these essential elements function within an automatic transmission.
Bands in Automatic Transmissions
Within an automatic transmission, bands are literally steel straps that encircle sections of the gear train and connect to the transmission housing. These bands aren’t just static components; they are dynamically engaged and disengaged by hydraulic cylinders located inside the transmission case.
Caption: An automatic transmission band, a key component in controlling gear ratios.
The image above illustrates a transmission housing with a band in place. The gear train itself has been removed for clarity. The metal rod you see is connected to a piston, which is responsible for actuating the band.
Caption: Hydraulic pistons that control the bands in an automatic gearbox, enabling gear changes.
As shown above, two pistons actuate the bands in this particular transmission. Hydraulic pressure, precisely directed into the cylinder by a valve system, forces these pistons to push against the bands. This action tightens the band around a specific part of the gear train, effectively locking that section to the stationary transmission housing. By holding certain parts of the gear train stationary, the bands play a crucial role in establishing the different gear ratios needed for varying driving conditions.
Clutches in Automatic Transmissions
While bands are essential for holding components still, clutches in an automatic transmission are responsible for connecting and disconnecting power flow between different parts of the gear train. In this transmission model, there are four clutches, each operated by pressurized hydraulic fluid acting on a piston within the clutch assembly. Springs are incorporated to ensure the clutch disengages when hydraulic pressure is released, allowing for dynamic control.
Caption: A clutch mechanism within an automatic gearbox, responsible for engaging and disengaging power flow.
The image above shows a clutch piston and the surrounding clutch drum. Notice the rubber seal on the piston – a component commonly replaced during a transmission rebuild, highlighting the wear and tear these parts endure.
The internal workings of a clutch are revealed in the next image, showcasing alternating layers of clutch friction material and steel plates. The friction material has internal splines that interlock with a gear, while the steel plates have external splines that connect to the clutch housing.
Caption: Clutch plates with friction material in an automatic transmission, vital for power transfer.
These clutch plates, like the bands, are also replaced when a transmission is rebuilt, emphasizing their role as wear items.
The hydraulic system within the automatic gearbox how it works is the brain controlling these clutches and bands. Hydraulic pressure, channeled through passages in the shafts, is carefully managed to activate specific clutches and bands at precise moments. This intricate hydraulic control system dictates which gear is engaged at any given time, ensuring smooth and efficient operation of the automatic transmission.
