5.3.5 Torque converter operation
Note
In order for the working fluid (oil) to constantly fill the cavity of the impellers and cool, during the operation of the torque converter, it is continuously pumped from the oil box into the working cavity of the wheels by a pump and drained back into the oil box.
During the operation of the torque converter, the oil pumped into the working cavity of the wheels is captured by the blades of the rotating impeller and thrown outward by centrifugal force. Then it falls on the blades of the turbine wheel and, due to the pressure created in this case, sets it in motion together with the driven shaft. Further, the oil enters the blades of a fixed reactor, which changes the direction of the fluid flow, and then enters the pump wheel again, continuously circulating in a closed circle of the inner cavity of the impellers (as indicated by the arrow in Figure 5.19), while participating in the general rotation of the wheels.
Note
The availability of a stationary reactor, the blades of which are located so that they change the direction of the liquid flow passing through it, contributes to the creation of a certain force on the reactor blades. This force causes the creation of a reactive moment, which acts through the liquid on the turbine wheel blades, in addition to the moment transmitted to it from pump wheel. Thus, the availability of this reactor makes it possible to obtain a torque on the shaft of the turbine wheel, which is different from the torque transmitted by the engine.
The slower the turbine wheel rotates in comparison with the impeller (for example, when the load from the car's movement downhill), the more the reactor blades change the direction of the working fluid flow passing through it, and the more additional torque is transferred from the reactor to the turbine wheel, due to which increases the torque on its shaft.
Note
The property of torque converters to automatically change (or transform) the ratio of torques on the shafts, depending on the ratio of the number of revolutions on the driving and driven shafts (and, therefore, on the magnitude of the external load) is their main feature. Thus, the action of the torque converter is similar to the action of a gearbox with an automatic change in gear ratios.
Interesting
The maximum value of the coefficient of performance (COP) for existing designs of torque converters ranges from 0.85-0.90.
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