Interrelated power delivery controls – including engine control – Transmission control – Transmission controlled by engine
Utility Patent
1999-07-21
2001-01-02
Ta, Khoi Q. (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Transmission controlled by engine
C477S158000, C477S160000
Utility Patent
active
06168547
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a line pressure control device for an automatic transmission.
BACKGROUND OF THE INVENTION
An automatic transmission for a vehicle is provided with a line pressure control device which comprises an oil pump and a pressure regulator valve. The line pressure control device controls the line pressure supplied to a speed ratio varying mechanism which varies a speed ratio and a clutch mechanism which switches a direction of transmission of the drive force. Tokkai Hei 8-28646 published by the Japanese Patent Office in 1996 discloses a line pressure control device which raises a line pressure in response to torque input into the transmission.
SUMMARY OF THE INVENTION
However, when a line pressure is set according to the input torque, although it is possible to set a high line pressure which increases together with increases in input torque of the transmission, that is to say, as transmitted torque increases, noise in the oil pump increases as line pressure rises. On the other hand, when a low line pressure is set, although it is possible to reduce pump noise, it is difficult to satisfy oil pressure requirements of the transmission which increase with increases in input torque.
Therefore it is difficult to achieve both oil pressure requirements in the transmission and reductions in pump noise when a line pressure is set only in response to input torque.
It is therefore an object of this invention to satisfy required oil pressures in the transmission while reducing pump noise.
In order to achieve the above object, this invention provides a line pressure control device for an automatic transmission, the transmission comprising a speed ratio varying mechanism and a clutch mechanism for transmitting rotation of an engine to an output shaft. The line pressure control device comprises an oil pressure circuit for varying a line pressure supplied to the speed ratio varying mechanism and the clutch mechanism, a sensor for detecting a rotation speed of the engine.
The line pressure control device further comprises a microprocessor programmed to calculate a lubrication pressure for lubrication of the speed ratio varying mechanism and a clutch pressure for an operation of the clutch mechanism based on an operating condition of the transmission, determine whether the rotation speed of the engine is higher or lower than a fixed threshold, set a target line pressure to the higher of the lubrication pressure and the clutch pressure as a target line pressure, when the rotation speed of the engine is higher than the threshold, set the clutch pressure as the target line pressure when the rotation speed of the engine is lower than the threshold and control the oil pressure circuit so that the line pressure equals the target line pressure.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.
REFERENCES:
patent: 4191072 (1980-03-01), Ehrlinger et al.
patent: 5085107 (1992-02-01), Tatara
patent: 5749804 (1998-05-01), Toukura
patent: 19934682 (2000-02-01), None
patent: 8-28646 (1996-02-01), None
patent: 9-112671 (1997-05-01), None
Foley & Lardner
Nissan Motor Co,. Ltd.
Ta Khoi Q.
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