Hydraulic automatic transmission control system
The automatic transmission hydraulic control system is used to change gears in an automatic transmission (AT). It consists of several components:
Oil pump
* Ensures a constant flow of hydraulic fluid (transmission fluid) in the system.
Torque converter
* A hydraulic device that transmits torque from the engine to the automatic transmission, ensuring smooth gear shifting.
Hydraulic unit
* Is the ‘brain’ of the hydraulic system. It directs the flow of hydraulic fluid to various valves and pistons to control gear shifting.
Electronic control unit (ECU)
* Monitors signals from various sensors and controls the hydraulic unit for automatic gear shifting.
Valves and pistons
* Valves control the flow of hydraulic fluid and pistons move friction packs to engage different gears.
Transmission cooler
* Cools the hydraulic fluid circulating in the system.
How does the automatic transmission hydraulic control system work:
1. Starting the engine: The oil pump begins to pump hydraulic fluid through the system.
2. Gear selection: The driver selects a gear using the gear selector.
3. Electronic control unit (ECU): The ECU receives signals from the sensors and calculates the required gear shift.
4. Valve block: The ECU directs the flow of hydraulic fluid to the corresponding valves and pistons in the valve block.
5. Gear Shift: Valves and pistons are activated, directing hydraulic fluid to the required friction packs. This causes the requested transfer to be enabled.
6. Pressure adjustment: The ECU regulates the hydraulic fluid pressure to ensure smooth gear shifting.
7. Transmission Cooler: The hydraulic fluid circulating in the system is cooled in the transmission cooler to prevent overheating.
The hydraulic automatic transmission control system ensures smooth and efficient gear shifting, which increases driving comfort and the service life of the automatic transmission.