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Dana torque converter: What is the function of a hydraulic torque converter?
Release date:
2022-11-14 13:46
Source:
Like a clutch, the torque converter is used to transmit power—but it does so in a flexible manner. Unlike a rigid clutch, it not only transmits torque but can also vary it. Its applications are extensive: it is indispensable in automotive automatic transmissions (ATs), and it is also widely employed in construction machinery, such as hydraulic torque converters found on loaders (forklifts).
The torque converter consists of a pump impeller, a stator, and a turbine. The pump housing is mounted on the engine’s flywheel, directly driving the pump impeller to rotate. Like the clutch pressure plate, the pump impeller can be regarded as the driving disc. It is connected to the transmission’s input shaft and serves as the power‑output shaft, analogous to the clutch disc, which functions as the driven disc. Its primary role is to modify torque. If the stator is removed, the assembly becomes a fluid coupling.
Because they all rely on hydraulics to transmit power, they can effectively dampen vibrations and shocks. Vibrations and impacts from the load have no adverse effect, resulting in a smoother driving experience. Moreover, they offer excellent gear‑shifting performance: the input shaft speed can exceed or fall below the output shaft speed, and the torque varies with the speed difference between the two. When the load is light, the speed increases; when the load is heavy, the speed automatically decreases, keeping the system operating within its most efficient range.
The housing consists of two halves: a front half and a rear half. The rear half is integrally connected to the pump impeller. After the three working wheels are installed within the housing, the two halves are welded together (or fastened with bolts) to form a sealed cavity that is filled with working fluid.
The crankshaft drives the pump impeller to rotate; the centrifugal force generated by this rotation causes the working fluid between the impeller blades to be thrown outward from the inner rim toward the outer rim. This portion of the working fluid possesses both a circumferential component of velocity, rotating in tandem with the impeller, and an axial component of velocity directed along the axis.
The velocity Vc of the working fluid exiting the turbine can be regarded as the vector sum of the component velocity Va, which is relative to the blade surface, and the rotational component velocity Vb, which follows the rotation of the blades. When the rotational speed is relatively low, the exiting working fluid flows backward, impinging on the front side of the blades. Since the one-way clutch prevents backward rotation, this rearward flow is redirected to propel the blades forward, thereby enhancing the rotational motion and increasing the torque.
As the rotational speed increases, the tangential velocity Vb also grows. When the resultant velocity Vc of Va and Vb begins to point toward the rear side, the Torque Converter reaches its critical point. With further increases in speed, the working fluid impinges on the rear side. Since the one-way clutch allows them to rotate forward together, the stator freely spins in the direction of rotation driven by the working fluid, enabling smooth backflow. When the exiting working fluid is precisely aligned with the outlet direction, the Torque Converter no longer provides torque multiplication—that is, it operates in the hydraulic coupling mode.
Dana torque converter
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