Fig. 4.34. Location of sensors in an automatic transmission: 1 – pressure sensor; 2 – output speed sensor; 3 – electromagnetic valve for controlling the flow of cooling liquid; 4 – input speed sensor
The vehicle is equipped with a four-speed automatic transmission model DDO with electrical control. The main gear and differential are built into the transmission. The transmission design includes a torque converter, planetary mechanisms, clutches and brakes with hydraulic control. The transmission is controlled by commands from the engine ECU through electrically controlled valves. The following sensors are installed in the transmission: input speed sensor, output speed sensor, electromagnetic valve for controlling liquid cooling and pressure sensor (Fig. 4.34).
The torque converter transmits power from the engine to the gearbox through fluid, allowing the car to start smoothly and change gears. In addition, the torque converter changes torque during acceleration. The Lock Up system or torque converter lockup allows for a direct connection between the automatic transmission and the engine. This is achieved using a "mini-friction clutch" located inside the torque converter. The Lock Up system is controlled by the gearbox 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 planetary links are stopped, or connected to each other, or free to rotate. The links are stopped and connected using brakes and clutches, which are activated by a hydraulic control unit. A hydraulic pump inside the box provides fluid pressure to control the clutches and brakes.
The signals from various sensors and switches installed in the gearbox, throttle body and selector mechanism are sent to the ECU, where they are processed to decide on the required gear selection at that moment. The ECU controls the electromagnetic valves that open or close channels inside the hydraulic control unit, engaging or disengaging the various clutches and brakes of the corresponding planetary gear sets, selecting the required gear in each case depending on the speed and engine load. The driver can override the 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 pressing the brake pedal.
The fluid in the gearbox is cooled by passing through a cooler mounted on top of the gearbox. The engine cooling system fluid also passes through the cooler.
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Due to the complexity of the design, any repair and maintenance work on the gearbox must be performed by a specialist. The information provided in the following subsections contains only general provisions and some maintenance operations that the owner can perform himself.
The weight of the automatic transmission is 70 kg.