Transmission Oil Pump for Gear Shifting

Automatic Transmission Oil Pump
The Lubrication Oil Pump is the power source of the entire hydraulic system of an automatic transmission, and is generally directly driven by the engine. All automatic transmissions have a front pump driven by the engine, and some transmissions also have a rear pump driven by the output shaft. The functions of these two pumps are to provide a certain flow and pressure of hydraulic oil required by the transmission. The specific functions are as follows:
1. Fill and maintain the hydraulic torque converter at a certain pressure to ensure that the torque converter effectively transmits power and prevent cavitation;
2. Provide hydraulic oil to operate each clutch and brake to shift gears. A new clutch typically has a stroke of 1.9 mm and a piston area of 40-80 cm2. Regardless of leakage, its flow rate is required to be 10 liters per minute. Ensure that the coupling element can stably transmit torque without slipping under stable working conditions;

3. Provide pressure lubricating oil to all moving parts, about 4-10L per minute;
4. Supply oil for pressure regulating valves and solenoid valves in the control system system, approximately 4L per minute;
5. Replenish the leakage at the seal of the hydraulic component, approximately 0.05L/min;
6. Provide sufficient flow of lubricating oil to cool the automatic transmission.

Critical parameters:

Type of automatic transmission oil pump:

Vane type: Vane type variable displacement pumps use a slide located inside the pump housing to vary the size of the inlet and outlet ports according to the transmission's needs. This slide is moved against spring pressure by a small sample of the pump's output. The pump's slide keeps fluid flow at a minimum when the needs are not as high and provides maximum flow when necessary.

Gear type: The most common type of fixed displacement Gear Pump is the crescent pump. These pumps have two gears like other gear pumps, but they are designed with an outer gear with internal teeth and a smaller inner gear with external teeth. As these teeth mesh, they carry with them and force fluid from the inlet port to the outlet port. The gap narrows as it nears the outlet port. The gears then move the fluid through the outlet port to create transmission line pressure. These pumps have strict tolerances between the gears and the housing. Excessive wear dramatically reduces the output and efficiency of this pump.

Rotor type: The rotor type pump is similar to the crescent gear pump, except it has rotors instead of gears. The inside rotor drives the outside rotor. The gap between the rotors increases as it moves away from the inlet port and decreases as it moves closer to the outlet port. Use a feeler gauge to measure these clearances. This action creates the flow used to lubricate and operate the transmission's friction bands and clutches. These are also known as fixed-displacement pumps.