192 clutches and power-stop control – Vortex-flow drive and clutch – Including drive-lockup clutch
Reexamination Certificate
2000-04-20
2002-05-28
Lorence, Richard M. (Department: 3681)
192 clutches and power-stop control
Vortex-flow drive and clutch
Including drive-lockup clutch
19, 19, 19
Reexamination Certificate
active
06394243
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a clutch device with a housing containing a first fluid chamber and a second fluid chamber and with a piston of a friction clutch. The piston separates the first fluid chamber from the second fluid chamber and is axially movable with respect to a housing axis. The friction clutch can be actuated by applying a pressure difference in the fluid between the first fluid chamber and the second fluid chamber. The friction surfaces of the friction clutch are arranged in the first fluid chamber. Fluid can be supplied to the first fluid chamber and fluid can be removed from the first fluid chamber independent from the fluid pressure in the second fluid chamber in order to conduct frictional heat away from the friction clutch and its friction surfaces. Fluid passages through which fluid allocated to the first fluid chamber can flow are allocated to the friction surfaces.
2. Discussion of the Prior Art
One application of a clutch device of the type mentioned above in automobile engineering consists, for example, in that when starting by means of the clutch device a driven element, for example, the input shaft of a shift transmission, is brought as far as possible to the same speed as a drive unit, for example, an internal combustion engine. Depending on the driving torque that can be applied by the drive unit, substantial power losses occur in the clutch device, which can be designated in this connection as a “starting element”. In extreme cases, these power losses can correspond to the maximum engine output. The starting element should be able to resist such power losses even in extreme situations, for instance, when starting on a hill, specifically, with as little wear as possible over the life of the starting element.
According to a known solution, the starting element is formed by a torque converter with a frictional lockup clutch which is arranged in a drivetrain of the motor vehicle between a drive unit (internal combustion engine) and an automatic transmission and frequently has an integrated torsional vibration damper. A torque converter is extremely advantageous in many respects because it is suitable for high torques and, beyond this, can multiply torques. However, this is a comparatively complicated solution, particularly with respect to construction, since the torque converter has three parts (impeller, turbine, stator) which are rotatable relative to one another. Further, a fluid cooler (oil cooler, especially transmission cooler) associated with the torque converter must be constructed for comparatively large flows of fluid. Further, the starting behavior of the system is not alterable, which would be advantageous for optimizing the system with respect to cold starting, selecting between sports-style starting or comfortable starting, etc.
Another known solution consists in a wet clutch forming an integral component part of an automatic transmission; while this clutch can be regulated with respect to torque transmission, it is not capable of withstanding high power losses (at high engine outputs) as well, in contrast to the hydrodynamic torque converter. Further, in clutches of this kind which are integrated in the transmission relatively high friction losses occur as a result of the wet operation (Plansch operation) resulting in a correspondingly higher consumption of fuel (gasoline consumption).
Further, there also exist hydraulic clutches, or hydroclutches, as they are called, with an integrated lockup clutch which have a hydraulic circuit with an impeller wheel and a turbine wheel but without a stator wheel (and consequently without torque multiplication. Hydroclutches of this type only operate fairly economically when the hydraulic circuit is utilized only for starting and when the lockup clutch which is constructed as a friction clutch is closed as quickly as possible.
For examples of a hydroclutch and a torque converter, each with an integrated lockup clutch formed as a friction clutch, reference may be had to German Patent Application 198 28 709.7 (not yet laid open to public inspection) and DE 44 23 640 A1 which share the common feature that the clutch device is controllable via a two-line system in which an engagement state of the lockup clutch and a fluid flow through the clutch device are not adjustable independently from one another. FR 2 341 791 A1 discloses a torque converter with a lockup clutch which may be controllable via a three-line system with adjustment of an engagement state of the lockup clutch independent from adjustment of fluid flow through the converter and in which a laminated stack of the friction clutch is arranged in a fluid chamber containing a turbine wheel, a stator wheel and an impeller wheel.
A torque converter of the type mentioned above attributed to the Mercedes-Benz company is known from a German Engineers Association report entitled “Construction and Control of Slip-regulated Lockup Clutch in a Hydrodynamic Torque Converter [Aufbau und Steuerung einer schlupfgeregelten Überbrüickungskupplung im hydrodynamischen Drehmomentwandler]”, L. Hein, et. al, (VDI-Berichte No. 1175, 1995, pages
319-337).
The torque converter is controllable by means of a three-line system in such a way that a fluid flow through the first fluid chamber is adjustable independently from the fluid pressure in the second fluid chamber and is accordingly adjustable independently from the engagement state or disengagement state of the friction clutch. The friction clutch of the known torque converter has a laminated stack which is arranged in the first fluid chamber and through which oil flows in an intensive manner according to information contained in the above-cited reference in order to ensure that the removal of heat from the clutch which is designed for continuous slip is good even during high transmission torques. This reference does not indicate how the claimed intensive flow of oil through the laminated stack is ensured. It appears that the flow of oil through the laminated stack depends primarily on the fluid flow forming in the first fluid chamber rather than on the supply of fluid to and removal of fluid from the first fluid chamber, since neither the report nor the drawings contained therein refers to means for positive guidance of the fluid which ensure that a determined amount of fluid having a defined relationship to the amount of fluid introduced into or removed from the first fluid chamber flows through the laminated stack when a fluid circuit is produced through the first chamber by supplying an amount of fluid to the first fluid chamber and removing a corresponding amount of fluid from the first fluid chamber.
As was found in an examination of an actual design by the Mercedes-Benz company which was familiar to experts in this technical field and which essentially corresponds to the torque converter described in the article, the Mercedes-Benz converter is provided with an oil circulation through the first fluid chamber in the following way: The oil delivered by a pump is supplied through an annular channel between a pump hub and a stator support and is fed from there between the stator wheel and the impeller shell into the first fluid chamber. Inside the converter, the supplied oil flows primarily radially outward under the influence of centrifugal force. However, because of slits in the turbine wheel, oil can also flow in the axial direction to an outlet point between the turbine hub and stator wheel, the oil being drawn off from there through an annular channel between the stator support and the driven shaft.
Oil which is pressed outward in the radial direction by centrifugal force can flow radially inward again between the house and the rear of the turbine wheel; it then strikes the laminated stack and flows partly through a gap between an outer lamination or disk carrier and the turbine wheel past the laminated stack and partly (about 10% by rough approximation) through the laminations of the laminated stack.
Before reaching the outlet point betwe
Cohen & Pontani, Lieberman & Pavane
Lorence Richard M.
Mannesmann Sachs AG
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