Interrelated power delivery controls – including engine control – Transmission control – Transmission controlled by engine
Reexamination Certificate
2000-09-29
2002-06-04
Marmor, Charles A (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Transmission controlled by engine
C701S061000
Reexamination Certificate
active
06398693
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to improvement of a line pressure control unit of an automatic transmission including a continuously variable transmission.
BACKGROUND OF THE INVENTION
An automatic transmission comprising a continuously variable transmission such as a toroidal continuously variable transmission and a V belt continuously variable transmission for vehicles, controls speed change by oil pressure, and controls a line pressure which is an oil pressure acting on an oil pressure circuit, as a base pressure.
Tokkai Hei 8-324297 published by the Japanese Patent Office in 1996 discloses a control method wherein a line pressure a required line pressure for the automatic transmission is multiplied by a constant safety factor to calculate a target line pressure.
Further, Tokkai Hei 6-207567 published by the Japanese Patent Office 1994 discloses a method wherein a real line pressure is feedback controlled to the above-mentioned target line pressure.
SUMMARY OF THE INVENTION
The idea of performing feedback control of the line pressure by multiplying the required line pressure for control of an automatic transmission by a constant safety factor to give a target line pressure, can easily be inferred from the two above-mentioned examples of the prior art.
When setting the safety factor as a fixed value to determine the target line pressure, the setting of the safety factor must be based on the maximum value of variation. However, with such a setting, the safety factor becomes a large value and this causes a pump drive load to increase under feedback control.
It is therefore an object of this invention to provide a line pressure control unit for an automatic transmission for a vehicle which controls a line pressure so that the pump drive load is small under feedback control.
In order to achieve above object, this invention provides a line pressure control unit of an automatic transmission for a vehicle which performs feedback control of a line pressure of an automatic transmission, comprising: a line pressure solenoid valve which adjusts a line pressure, a sensor which detects a real line pressure, and a microprocessor which controls the line pressure solenoid valve, the microprocessor being programmed to: calculate a required line pressure according to the running state of the vehicle , calculate a target line pressure from the required line pressure, the target line pressure being modified by a safety factor for line pressure correction, and calculate a line pressure difference between the required line pressure and the real line pressure, and add a feedback control amount according to the line pressure difference to the target line pressure to calculate a command line pressure, control the line pressure valve based on the command line pressure.
REFERENCES:
patent: 4759236 (1988-07-01), Tezuka et al.
patent: 4949595 (1990-08-01), Shimanaka
patent: 4967620 (1990-11-01), Shimanaka
patent: 4999774 (1991-03-01), Tokoro et al.
patent: 5056380 (1991-10-01), Sawasaki et al.
patent: 5089964 (1992-02-01), Morishige et al.
patent: 5191815 (1993-03-01), Kouta
patent: 5776030 (1998-07-01), Minowa et al.
patent: 5800308 (1998-09-01), Tsutsui et al.
patent: 06-207567 (1994-07-01), None
patent: 406207657 (1994-07-01), None
patent: 406207658 (1994-07-01), None
patent: 08-324297 (1996-12-01), None
Foley & Lardner
Marmor Charles A
Nissan Motor Co,. Ltd.
Pang Roger
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