Interrelated power delivery controls – including engine control – Transmission control – Control by sensed ambient condition – pattern indicia,...
Reexamination Certificate
1999-03-16
2001-08-21
Ta, Khoi Q. (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Control by sensed ambient condition, pattern indicia,...
C477S143000, C477S156000
Reexamination Certificate
active
06277049
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a shift control system for an automatic transmission, and more particularly to a shift control system arranged to prevent an automatic transmission from generating an interlock during a shift executed by an engagement of one friction element and a disengagement of another friction element under a low temperature condition.
An automatic transmission shown in “A Service Manual of RE4R
0
lA type Automatic Transmission (A261C07)” published by Nissan Motor Co., Ltd. is arranged to execute a shift by engaging a friction element and by disengaging another friction element. The engagement of the friction element to be engaged is quickly executed even if a viscosity of hydraulic oil of the automatic transmission becomes high due to a low temperature because the pressurized hydraulic oil is supplied to the friction element to be engaged. In contrast, if the viscosity of the hydraulic oil is high under the low temperature condition, the disengagement of the friction element to be disengaged is delayed according to the increase of the viscosity of the hydraulic oil since the disengagement operation is executed by simply draining the hydraulic oil from the friction element to be disengaged. This time delay of the disengagement will degrade a shift feeling applied to a driver. A Japanese Patent Provisional Publication No. 8-233077 has proposed a shift control system arranged to forbid or disable a manual shift when a hydraulic oil temperature is low, in order to avoid a driver from feeling the degraded shift feeling of the manual shift under the low temperature condition.
SUMMARY OF THE INVENTION
However, a temporal interlock during shift in an automatic shift mode and a trouble due to the interlock under a low temperature will be not solved by the above-mentioned arrangement. Further, the forbidding or disabling of all of the shifts in the manual shift mode excessively decreases merits of an automatic transmission with a manual shift mode.
It is an object of the present invention to provide an improved shift control system which solves the problems caused under the low temperature condition even if the automatic transmission is set in the automatic shift mode.
A shift control system of an automatic transmission according to the present invention executes a shift from a first speed position to a second speed position. The shift control system with a manual shift mode comprises a first friction element, a one-way clutch, a second friction element, a first solenoid, a second solenoid, an oil temperature sensor, and a controller. The first friction element is engaged by pressure of hydraulic oil so as to put engine brake active when the first speed position is selected in the manual shift mode. The one-way clutch is engaged when the first position is selected in the automatic shift mode. The second friction element is engaged by pressure of hydraulic oil when the second speed position is selected in the manual shift mode or the automatic shift mode. The first solenoid varies a pressure of hydraulic oil applied to the first friction element according to a first signal. The second solenoid varies a pressure of the hydraulic oil applied to the second friction element according to a second signal. The oil temperature sensor detects a temperature of the hydraulic oil and outputs a temperature signal indicative of the temperature of the hydraulic oil. The controller outputs the first signal to the first solenoid to decrease the pressure of hydrulic oil and outputs the second signal to the second solenoid to engage the second friction element when the shift from the first shift position to the second shift position is executed in the manual shift mode. The controller delays the output of the second signal as compared with the output of the first signal when the temperature signal from the oil temperature sensor is lower than a predetermined temperature.
REFERENCES:
patent: 5558597 (1996-09-01), Oba et al.
patent: 5692991 (1997-12-01), Iwata et al.
patent: 5876301 (1999-03-01), Tabata et al.
patent: 5947856 (1999-09-01), Tabata et al.
patent: 5957807 (1999-09-01), Takamatsu et al.
patent: 8-233077 (1996-09-01), None
patent: 409021459A (1997-01-01), None
patent: 9-21459 (1997-01-01), None
English Language Translation of Document A1.
“A Service Manual of RE4R01A type Automatic Transmission (A261C07)”, published by Nissan Motor Co., Ltd.; (1987).
Foley & Lardner
Nissan Motor Co,. Ltd.
Ta Khoi Q.
Wright Dirk
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