Automatic transmission (pic. 3) It is arranged according to the traditional planetary scheme with onami friction braking and consists of a torque converter, a pump, a planetary gearbox, multi-plate clutches, multi-plate brakes and a valve block.
Pic. 3. Automatic transmission: 1 - torque converter housing; 2 - oil pan; 3 - mechanism for switching modes; 4 - gearbox housing; 5 - cover; 6 - electrical connector
torque converter acts as a clutch and serves to smoothly connect the engine and gearbox mechanism, as well as increase torque at the beginning of the car. The body of the torque converter is connected to the crankshaft of the engine through the drive disk 1 (pic. 4) and constantly rotates when the engine is running. The internal cavity of the torque converter is filled with a 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 flow of the 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.
Pic. 4. Torque converter: 1 - leading disk; 2 - torque converter 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, an automatic transmission range selection spool valve, auxiliary valves (solenoids), hydraulic accumulators, clutches and brakes. The pressure in the hydraulic system is generated by a pump. The pump ensures the operation of the torque converter, blocking clutches, brakes and lubrication of the gearbox parts. The pressure generated by the pump is adjusted according to vehicle speed and engine load. The pump is driven from the crankshaft of the engine.
Ravigne planetary gear (pic. 5) is a gear train with external and internal gears, which provides different ways of connecting its elements to obtain different gear ratios.
Pic. 5. Ravigne planetary gear: 1 - long satellite; 2 - carrier; 3 - small sun gear; 4 - a large sun gear; 5 - short satellite; 6 - ring gear
Principles of operation of multi-plate clutches (pic. 6) and disc brakes (pic. 7) very similar: the difference lies in the fact that the multi-plate clutch connects the gearbox links to each other, and the disc brake connects to the gearbox housing. The working fluid supplied to the clutch actuates the piston - the friction discs are compressed. The links blocked by the clutch begin to rotate in one piece.
Pic. 6. Scheme of operation of a multi-plate clutch: A - multi-plate clutch is on; B - multi-plate clutch is off; 1 - ball valve; 2 - sealing ring; 3 - piston; 4 - friction disc; 5 - friction disc with pads; 6 - thrust disk; 7 – coupling hub; 8 - spring stop; 9 - retaining ring; 10 - return spring
Pic. 7. Diagram of disc brake operation: A - brakes on; B - brakes are off; 1 - thrust disk; 2 - friction brake discs with pads; 3 - friction disc; 4 - return spring; 5 - piston; 6 - gearbox housing; 7 – a cover of a case of a transmission
When the disc brakes are turned off, the working fluid stops flowing into the clutch and the piston, under the action of a return spring, is set 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 prevents the clutch from unlocking. Additionally, a ball valve is installed in the coupling, which is located as close as possible to the edge from the center of the coupling. 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, which receives information about the state of the engine, driving conditions and selects the moment of gear shifting according to road conditions and taking into account the driver's driving style. The result is improved fuel economy and improved transmission performance. In addition, the electronic transmission control system provides a function for diagnosing malfunctions and switching to emergency operation 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 radiator of the engine cooling system.
Selector automatic transmission is installed in the same place on the floor tunnel as the manual transmission control lever, and is connected to the transmission shift mechanism by a control cable.
The automatic transmission differential is similar in design to the manual transmission differential.
A feature of the automatic transmissions of the Opel Astra J compared to previous generations is the ability to switch from fully automatic control mode to manual mode (so-called sequential gearbox), in which the driver, during the acceleration of the car, independently chooses the moment of switching to overdrive. This allows, if desired, to achieve more intensive acceleration compared to automatic mode, artificially delaying the upshift, and bring the engine speed to the maximum torque range. At the same time, the electronic control system constantly monitors the vehicle speed and engine load, eliminates driver error by not allowing him to shift into a higher gear at low speed to avoid engine overload, or downshift at too high a speed, which eliminates the possibility of exceeding the maximum allowable engine speed. When the vehicle speed decreases, the gears automatically switch to lower gears without the participation of the driver. When the car comes to a complete stop, 1st gear is automatically engaged.
To repair an automatic transmission, a large set of special tools, diagnostic equipment and appropriate training of the performer are required. If it is necessary to repair the gearbox, contact a specialized service.
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