Planetary gear transmission systems or components – Fluid drive or control of planetary gearing – Single impeller-turbine type fluid circuit divides or...
Patent
1998-10-26
1999-09-21
Wright, Dirk
Planetary gear transmission systems or components
Fluid drive or control of planetary gearing
Single impeller-turbine type fluid circuit divides or...
475 49, F16H 4500
Patent
active
059546077
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns a transmission unit and a method to drive a transmission unit.
2. Description of the Related Art
Transmissions which are equipped with both a mechanical transmission unit and a hydrodynamic transmission unit are well-known in numerous design variations. The hydrodynamic component of the transmission is typically designed to serve as a hydrodynamic coupling or hydrodynamic torque converter. These components, sometimes referred to as fluid drives, include an impeller and a turbine which together form at least one toroid-shaped operating zone. This space can be filled with an operating fluid, and this fluid is accelerated by the turbine and decelerated by the compressor. The resultant torque generation is essentially the result of inertia forces generated by the change in velocity of the fluid. The transmitted power is the product of the change in swirl (rotating momentum) of the fluid and the angular velocity. In addition to the compressor and turbine, a hydrodynamic torque converter also includes a "reactionary" component which is commonly referred to as stator. This stator is capable of absorbing torque. Since the sum of the moment forces in this circuitry has to equal zero, the torque of the turbine can, depending on the size and rotational direction of the stator torque, be larger, the same, or smaller than the torque induced by the compressor. In this manner, it is possible with the additional arrangement of only an impeller and a turbine, which is also referred to as hydrodynamic coupling, to substantially vary the rotational speed range and the torque of the turbine in relation to the impeller.
The transmitting of power hydrodynamically offers the advantages of being able to transmit significant power levels at high efficiency, low wear rates, and the use of transmission components that are comparatively small. Furthermore, these components are primarily used during run-up or during the initial acceleration phase of a vehicle that utilizes a power-generating device, as well as a power-consuming device. In transmission designs that are equipped with a hydrodynamic coupling as well as a gearbox, the hydrodynamic coupling serves the function of a "start-up" clutch. The torque or power transmission occurs consequently via the hydrodynamic unit only in first gear, usually during the initial acceleration phase. In other gears, the hydrodynamic unit is excluded from transmitting power. In addition, the transmission unit can include another fluid dynamic device such as a hydrodynamic retarder whose purpose it is to provide braking. This retarder can be an integral part of the transmission or can be an attachment to the transmission. The same task can also be performed by hydrodynamic torque converters which can work, in the lower gears, in a power-sharing mode together with the mechanical gears. Thereby, the hydrodynamic torque converter is usually used during the initial acceleration phase as a "start-up" or acceleration device. In the remaining gears, the power will be transmitted on a purely mechanical basis by bypassing the hydrodynamic converter. In the lower gears, the power will be transmitted via the hydrodynamic torque converter and the mechanical gearing of the transmission.
The present developments in the automobile industry are partially characterized by conflicting trends. In addition to the trends for more design space, more comfort and improved vehicle acceleration and deceleration behavior for the purpose of improved safety for all vehicles, the aspect of environmental protection increases in significance. One possibility of lowering CO.sub.2 emissions that are emitted by automobiles is the improvement of the energy conversion process (mechanical efficiency) of the drive train between the engine and the power consumer. Furthermore, the trend is to use smaller engines with smaller displacements which translates into lower torque and higher rated engine speeds. These are the requirements by which vehicle transmissions
REFERENCES:
patent: 4413535 (1983-11-01), Hobbs
patent: 4583426 (1986-04-01), Chassagnette et al.
"Voith--Hydrodynamic in Drive Technology", Krauskopf Engineering Digest, 1997.
Englisch Andreas
Nitsche Martin
Voith Turbo GmbH & Co. KG
Wright Dirk
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