Pic. 4.34. The location of the sensors in the automatic transmission: 1 - pressure sensor; 2 – output speed sensor; 3 - solenoid valve for controlling the flow of liquid for cooling; 4 - input speed sensor
The car is equipped with a four-speed automatic transmission model DDO with electrical control. The main gear and differential are built into the gearbox. The gearbox design includes a torque converter, planetary gears, clutches and hydraulically controlled brakes. The gearbox is controlled by commands from the engine ECU through electrically controlled valves. The following sensors are installed in the box: input speed sensor, output speed sensor, liquid cooling control solenoid valve and pressure sensor (pic. 4.34).
The torque converter transfers power from the engine to the transmission through the fluid, resulting in smooth starting and shifting. In addition, the torque converter provides a change in torque during acceleration. The Lock Up system, or torque converter lock-up, allows a direct connection between the automatic transmission and the engine. This is implemented using «mini friction clutch», placed inside the torque converter. The Lock Up system is controlled by the transmission ECU.
The planetary part of the gearbox provides four forward gears and one reverse gear. The gear ratio of the gearbox depends on which of the links of the planetary mechanism are stopped, or connected to each other, or rotate freely. Stopping and connection of links is carried out with the help of brakes and clutches, which are activated by a hydraulic control unit. A hydraulic pump inside the box provides fluid pressure to operate the clutches and brakes.
Pulses from various sensors and switches installed in the gearbox, throttle body and selector mechanism enter the ECU, where they are processed to decide on the choice of the currently required gear. The ECU controls solenoid valves that open or close passages within the hydraulic control unit, engaging or disengaging the various clutches and brakes of the respective planetary gears, selecting the appropriate gear on a case-by-case basis depending on speed and engine load. The driver can ignore information from the ECU computer by moving the gear selector lever and selecting a gear regardless of engine speed.
The Shift Lock system prevents the selector lever from being moved without simultaneously depressing the brake pedal.
The fluid in the gearbox is cooled by passing through a cooler mounted on top of the gearbox. The engine coolant also passes through the cooler.
Due to the complexity of the design, any work on the repair and maintenance of the gearbox must be carried out by a specialist. The information in the following subsections contains only general provisions and some maintenance operations that the owner can perform on his own.
The weight of the automatic transmission is 70 kg.