Interrelated power delivery controls – including engine control – Clutch control – With fluid drive
Reexamination Certificate
1999-11-03
2001-04-17
Estremsky, Sherry (Department: 3681)
Interrelated power delivery controls, including engine control
Clutch control
With fluid drive
C477S064000, C477S176000, C192S003310
Reexamination Certificate
active
06217481
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to improvements in a slip control system which converges a slip rotation speed between input and output elements of a torque converter at a target value, and more particularly to a slip control system which suitably functions even during a transient period from the non slip-control range to a slip control range.
Generally, a torque converter has merits such as a torque fluctuation absorbing function and a torque multiplying function due to a fluid power transmission, although a transmission efficiency of the fluid power transmission is lower than that of a power transmission by a direct mechanical connection. In order to improve the transmission efficiency of the torque converter, most torque converters employ lockup clutches for directly connecting input and output elements of the torque converter when the vehicle is put in a running condition where the torque fluctuation absorbing function or the torque multiplying function are not required. Further, some of lockup torque converters have been proposed to execute a slip control of a lockup clutch. Such a slip control for a torque converter is generally arranged to determine a target slip rotation speed according to a vehicle running condition and to control an engagement force of the lockup clutch so as to adjust an actual slip rotation speed to the target slip rotation speed.
SUMMARY OF THE INVENTION
However, such a slip control system, which is arranged to estimate an output torque of the torque converter on the basis of a modeled torque converter and a modeled engine, is required to be further improved. More specifically, the slip control system is required to suitably operate even if the correspondence between the modeled objects and the controlled objects is degraded by errors in modeling, aging of the controlled objects, or deviation among controlled objects. Inventers of this invention have executed various simulations upon taking account of the degradation of this correspondence, and found that such degradation of the correspondence in some cases degrades the operational performance of the torque converter during a starting period of the slip control.
It is therefore an object of the present invention to provide an improved slip control system that solves the degradation of operational performance of a torque converter.
According to the present invention, a slip control system for a torque converter with a lockup clutch is arranged to control an actual slip rotation speed between input and output elements of the torque converter at a target slip rotation speed. The torque converter is connected to an engine and a transmission of a vehicle. The slip control system comprises a vehicle operation condition detector detecting operating condition of the vehicle, an actuator controlling a lockup clutch engagement pressure of the lockup clutch according to a control signal to adjust the actual slip rotation speed at the target slip rotation speed and a controller connected to the vehicle operating condition detector and the actuator. The controller is arranged to decide an operating state of the torque converter when the slip control is started, to decide an initial value of a slip rotation speed command value according to the operating state of the torque converter at the start of the slip control, to calculate the slip rotation speed command value on the basis of the detected vehicle operating condition, and to output the control signal corresponding to the slip rotation speed command value to the actuator.
REFERENCES:
patent: 5722912 (1998-03-01), Narita
patent: 5935043 (1999-08-01), Watanabe et al.
patent: 6039675 (2000-03-01), Adachi et al.
patent: 6050919 (2000-04-01), Kusafuka et al.
patent: 10-333703 (1998-12-01), None
Adachi Kazutaka
Watanabe Akira
Estremsky Sherry
McDermott & Will & Emery
Nissan Motor Co,. Ltd.
Waddell Tisha D.
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