The torque converter uses oil to send torque from the engine to the transmission. When the machine is working against a load, the torque converter can multiply the torque from the engine. The torque converter then sends a higher torque to the transmission.
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| Illustration 1 | g00278199 |
Torque Converter (1) Housing. (2) Turbine. (3) Stator. (4) Impeller. (5) Pump drive gear. (6) Carrier. (7) Outlet passage. (8) Inlet passage. (9) Hub. | |
The oil for the operation of the torque converter comes from the oil pump for the transmission. The oil pump is driven by pump drive gear (5). The oil flows to a flow control valve in the transmission case. The oil flow is divided at the flow control valve. Oil is directed to the transmission circuit and to the torque converter circuit. The torque converter inlet oil pressure is controlled by the torque converter inlet relief valve. The converter inlet relief valve is mounted in the transmission case below the transmission control valve. The relief valve limits the maximum pressure to the torque converter to 900 ± 70 kPa (130 ± 10 psi). The torque converter inlet relief valve protects the torque converter from high pressure that is due to cold oil or due to some other restriction in the torque converter or in the cooler circuit.
Housing (1) is connected to the engine flywheel with splines. Impeller (4) and gear (5) for the oil pump are connected to the rotating housing. These components turn with the engine flywheel at the engine speed.
Stator (3) is connected to carrier (6). The carrier is fastened to the transmission cover. The stator does not turn.
Turbine (2) is connected to hub (9) by splines. Hub (9) is connected to the transmission input shaft by splines.
Oil from the hydraulic controls of the transmission flows into the torque converter through inlet passage (8) in carrier (6). This oil flows to impeller (4). The rotation of the impeller provides the oil with force.
Impeller (4) turns with the rotating housing (1) at the engine speed. The rotation of the impeller causes the oil to move to the outside of the impeller. The oil then goes around the inside of housing (1) and against the blades of turbine (2). The force of the oil that hits the turbine blades causes turbine (2) and hub (9) to turn. This sends torque to the input shaft of the transmission. Now, the turbine torque that is provided by the force of the oil from the impeller cannot be more than the torque output of the engine to the impeller.
After the oil hits the turbine blades, the oil goes toward the inside of turbine (2). As the oil goes from the turbine, the oil moves in the direction that is opposite the impeller rotation. Stator (3) causes the oil to change direction. The oil flows back into impeller (4) in the direction of rotation.
The force of the oil from the stator can now add to the torque output from the engine to the impeller. This extra force can provide an increase to the torque output of the engine to the turbine. As the difference between the turbine speed and the speed of the impeller becomes larger, the amount of force from the oil of the stator increases.
The load on the machine is the cause of speed changes of the turbine. This means that a higher load causes the difference in the speed of the impeller and the turbine speed to be larger. The force from the oil of the stator adds a certain amount of torque multiplication. The different loads on the machine control the amount of torque multiplication. The torque multiplication of the torque converter is at the maximum when the torque converter is stalled. The torque converter is stalled when the output shaft rpm is zero. Oil from outlet passage (7) flows to the oil cooler. The oil then flows to the lubrication system.