Interrelated power delivery controls – including engine control – Transmission control – Continuously variable friction transmission
Patent
1999-01-07
2000-05-23
Wright, Dirk
Interrelated power delivery controls, including engine control
Transmission control
Continuously variable friction transmission
477 39, F16H 6114
Patent
active
060660694
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a control system for control of a lock-up clutch in a continuously variable transmission.
BACKGROUND OF THE INVENTION
Hydrodynamic torque converters in automatic transmissions chiefly perform the task of making possible a comfortable starting operation with an increased start-up torque and to uncouple the torsional vibrations of the engine from the drive line. With the constantly increasing demands for reducing both fuel consumption and gas emission, it has become necessary further to reduce the losses in the hydrodynamic torque converter. In the first place, this is achieved by optimizing the torque converter itself and by using a (slip regulated) lock-up clutch. The latter objective is to reduce the share of the comfortable but dissipative hydrodynamic power transmission and thus to spare fuel without giving up a sufficient uncoupling of vibrations.
The control of the lock-up clutch essentially consists of a strategy and pressure modulation. In the strategy established is which state the torque converter lock-up clutch assumes, by taking into consideration an optimal consumption and comfort characteristic. At least two basic states (open and closed) have been defined. Together with that, a slipping operation of the torque converter lock-up clutch can be implemented.
DE-A 41 04 542 has disclosed a control system for control of a lock-Lip clutch in a continuously variable transmission. For control a ratio of the speeds of rotation of the input engine and of the primary pulley of the continuously variable transmission is formed. If this value is one, the torque converter lock-Lip clutch is closed. By comparing an actual ratio between the primary and secondary pulleys of the continuously variable transmission with the computed theoretical ratio, it is determined that the torque converter must be activated. In this case, a disengagement signal is generated to disengage the torque converter lock-up clutch. With the engagement and disengagement, time steps become effective in order to ensure that the secondary pressure is adapted to the torques to be transmitted--in accordance with the operating state of the torque converter lock-up clutch. The strategy takes into consideration the basic, functions for control of a torque converter lock-up clutch.
SUMMARY OF THE INVENTION
The problem on which the invention is based is to provide a strategy for control of a lock-up clutch which is a component part of an operating strategy for a continuously variable transmission. A control system for a continuously variable transmission (17) of a motor vehicle having a torque converter (2) with a lock-up clutch (10), especially for control of the lock-up clutch, for locking up the torque converter and means (31 to 42) for detecting input signals which are derived from a driver-vehicle system and processed to an engagement and disengagement signal in accordance with the detected states, characterized in that said lock-up clutch (10) is controlled following a strategy in which the hydrodynamic torque converter (2) is considered as hydrodynamic variator serially mounted with the continuously mounted with the continuously variable transmission (17) and an en disengagement of the lock-up clutch (10) is exclusively function of the control of the engine theoretical speed of rotation (n.sub.-- Mot.sub.-- soll).
BRIEF DESCRIPTION OF THE DRAWING(S)
Other features essential to the invention and the advantages resulting therefrom are to be understood from the description that follows of an embodiment with reference to the drawings. The drawings show:
FIG. 1 is a diagram of a continuously variable transmission within a motor vehicle;
FIG. 2 is a graphic representation for explaining the engagement and disengagement conditions; and
FIG. 3 is a variogram of the continuously variable transmission.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
FIG. 1 diagrammatically shows a continuously variable transmission: an input unit 1, preferably an internal combustion engine, drives a start-up unit, preferably a hydrody
REFERENCES:
patent: 4393467 (1983-07-01), Miki et al.
patent: 5112280 (1992-05-01), Sato
patent: 5158163 (1992-10-01), Suzuki
patent: 5160003 (1992-11-01), Suzuki
Wright Dirk
ZF Friedrichshafen AG
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