The automatic transmission (Fig. 3) is designed according to the traditional planetary scheme with friction braking and consists of a torque converter, pump, planetary gearbox, multi-plate clutches, multi-plate brakes and a valve block.
Fig. 3. Automatic transmission: 1 – hydraulic transformer housing; 2 – oil pan; 3 – mode switching mechanism; 4 – gearbox housing; 5 – lid; 6 – electrical connector
Torque converter acts as a clutch and serves to smoothly connect the engine and gearbox mechanism, as well as increase the torque at the start of the vehicle's movement. The torque converter housing is connected to the engine crankshaft via the drive disk 1 (Fig. 4) and rotates constantly when the engine is running. The internal cavity of the torque converter is filled with working fluid for automatic transmissions. The engine rotates the torque converter and drives the pump wheel, which creates flows of working fluid in the direction of the turbine wheel. The turbine wheel begins to rotate due to the flows of working fluid created by the pump wheel. With a large difference in the speeds of rotation of the turbine and pump wheels, the reactor changes the direction of the fluid flow, increasing the torque. As the speed difference decreases, it becomes unnecessary and is therefore installed on the overrunning clutch.
Fig. 4. Torque converter: 1 – leading disk; 2 – hydraulic transformer housing; 3 – turbine; 4 – overrunning clutch; 5 – reactor; 6 – pump wheel
The hydraulic control system of the automatic transmission includes a pump, a pressure regulator, a spool valve for selecting the automatic transmission range, auxiliary valves (solenoids), hydraulic accumulators, clutches and brakes. The pressure in the hydraulic system is created by a pump. The pump ensures the operation of the torque converter, locking clutches, brakes and lubrication of the transmission parts. The pressure created by the pump is regulated depending on the speed of the car and the load on the engine. The pump is driven by the crankshaft of the engine.
The Ravigne system planetary gearbox (Fig. 5) is a gear transmission with external and internal gear engagements, which provides different ways of connecting its elements to obtain different gear ratios.
Fig. 5. Planetary gearbox of the Ravigne system: 1 - long satellite; 2 – driver; 3 – small sun gear; 4 – large sun gear; 5 - short satellite; 6 – ring gear
The operating principles of multi-plate clutches (Fig. 6) and disc brakes (Fig. 7) are very similar: the difference is that a multi-plate clutch connects the gearbox links to each other, and a disc brake connects to the gearbox housing. The working fluid supplied to the clutch activates the piston - the friction disks are compressed. The links locked by the clutch begin to rotate as a whole.
Fig. 6. Operation diagram of a multi-plate clutch: A - multi-plate clutch engaged; B - multi-plate clutch disengaged; 1 – ball valve; 2 – sealing ring; 3 – piston; 4 – friction disc; 5 – friction disc with linings; 6 – thrust disc; 7 – clutch hub; 8 – spring stop; 9 – retaining ring; 10 – return spring
Fig. 7. Disc brake operation diagram: A - brakes on; B - brakes off; 1 – thrust disc; 2 – friction brake discs with linings; 3 – friction disc; 4 – return spring; 5 – piston; 6 – gearbox housing; 7 – gearbox housing cover
When the disc brakes are disengaged, the working fluid stops being supplied to the clutch and the piston, under the action of the return spring, returns to its original position.
The design feature of the multi-plate clutch is that it is in constant rotation, and under the action of centrifugal force acting on the working fluid, pressure is created that does not allow the clutch to unlock. Additionally, a ball valve is installed in the clutch, which is located as close as possible to the edge of the center of the clutch. When the pressure of the working fluid in the chamber of the multi-plate clutch increases, the ball valve closes the drain hole, and when the pressure in the chamber decreases, the ball valve opens the drain hole under the action of centrifugal force - the clutch is unlocked.
Gears in an automatic transmission are shifted using an electronic control unit that receives information about the engine condition, driving conditions and selects the moment of gear shifting according to road conditions and the driver's driving style. As a result, fuel efficiency increases and the transmission's performance is improved. In addition, the electronic transmission control system has a function for diagnosing faults and switching to emergency mode when they occur.
An aluminum heat exchanger with a tubular-ribbon core is used to cool the transmission fluid. It is installed in front of the engine cooling system radiator.
Selector the automatic transmission control lever is mounted in the same location on the floor tunnel as the manual transmission control lever and is connected to the transmission shift mechanism by a control cable.
The differential of an automatic transmission is similar in design to the differential of a manual transmission.
A special feature of the automatic transmissions of the Opel Astra J compared to the previous generations is the ability to switch from fully automatic control mode to manual mode (the so-called sequential gearbox), in which the driver independently selects the moment of switching to an upshift during acceleration of the car. This allows, if desired, to achieve more intense acceleration compared to the automatic mode, artificially delaying the switching to an upshift, and to bring the engine crankshaft speed to the maximum torque range. At the same time, the electronic control system constantly monitors the car speed and engine load, eliminates driver errors, not allowing him to engage a higher gear at low speed to avoid engine overload, or a downshift at too high a speed, which eliminates the possibility of exceeding the maximum permissible engine crankshaft speed. When the car speed decreases, the gears are automatically switched to lower ones without driver intervention. When the car comes to a complete stop, the first gear is automatically engaged.
Repairing an automatic transmission requires a large set of special tools, diagnostic equipment and appropriate training of the performer. If you need to repair the transmission, contact a specialized service.
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