Jatco Corporation

Jatco Transtechnology Ltd.

Takashi Sano

Takashi Murasugi

Kazunari Otake

Ikuo Hirose

Yuuji Saitou

In a shift control system for an automatic transmission, shelf-pressure control means include means for increasing the engagement pressure of the friction elements at a first gradient as previously set after output of the shift command, wherein after output of the shift command and when start of the inertia phase is detected, a torque-reduction command is output to the torque-reduction control means, the engagement pressure at detection of the inertia phase is set as an initial shelf pressure to increase the shelf pressure at a second gradient set for each speed, and a torque variation part oil pressure is added only when detecting a variation in throttle opening, and wherein after start of the inertia phase and when completion of the inertia phase is detected, a torque-reduction completion command is output to the torque-reduction control means. With this, the shelf pressure can be set appropriately during inertia phase without needing an enormous data amount even if a variation in throttle opening is present.

Shift control system for automatic transmission

A shift control apparatus is arranged to effect a shift in an automatic transmission by changeover of friction elements to be engaged with disengagement of a disengagement-side friction element and engagement of an engagement-side friction element. A shift controller is configured to detect an end of a loss stroke in the engagement-side friction element, and performs an operation to decrease the disengagement-side working oil pressure at a set gradient and to increase the engagement-side working oil pressure at a predetermined gradient upon detection of the end of the loss stroke in the engagement-side friction element. The predetermined gradient of the engagement-side working oil pressure for the engagement-side friction element is made lower for a low engine load than for a high engine load.

Shift control apparatus of automatic transmissions

An automatic transmission has a frictionally engaging element, such as a low-and-reverse brake or the like, that is hydraulically actuated for assuming a certain gear position. A hydraulic control system for the transmission comprises a first hydraulic section which produces a line pressure; a solenoid which produces a solenoid pressure; a decompression control valve which receives the line pressure to produce an output pressure while using both the solenoid pressure and the output pressure as signal pressures; a switching valve interposed between the decompression control valve and the frictionally engaging element. The switching valve has a first position wherein the output pressure is fed to the frictionally engaging element and a second position wherein the line pressure is fed to the frictionally engaging element. The hydraulic control system further comprises a second hydraulic section that keeps the switching valve at the first position when a signal pressure applied thereto is lower than a predetermined switching pressure and turns the switching valve to the second position when the signal pressure becomes higher than the predetermined switching pressure.

Hydraulic control system of automotive automatic transmission

A shift control system of an automatic transmission executes an interchange shift by interchanging engagement conditions of first and second friction elements of the automatic transmission. The first and second friction elements are engaged and disengaged according to oil pressures supplied thereto. A controller of the shift control system is arranged to decrease the second oil pressure of the second friction element by a second predetermined gradient and to increase the first oil pressure of the first friction element by a first predetermined gradient after the loss stroke of the first friction element is terminated, and to determine the first gradient such that a difference between a command pressure and an actual pressure of the first friction element is kept substantially constant.

An automatic transmission has a low clutch that assumes its engaged condition at a plurality of lower gear positions of D-range and a high clutch that assumes its engaged condition at a plurality of higher gear positions of D-range, A hydraulic control system for the transmission comprises a hydraulic section that produces a line pressure; a solenoid valve that produces a solenoid pressure upon receiving a solenoid signal; a first pressure control valve that produces a first output pressure from the line pressure by using the solenoid pressure and the first output pressure as operation signal pressures, the first output pressure having a smaller gain with respect to the solenoid pressure; a second pressure control valve that produces a second output pressure from the line pressure by using the solenoid pressure and the second output pressure as operation signal pressures, the second output pressure having a larger gain with respect to the solenoid pressure; and a switching valve that selectively assumes a first position to feed the low clutch with the first output pressure when the engagement of said low clutch brings about a higher gear position that needs a smaller torque contribution, and a second position to feed the low clutch with the second output pressure when the engagement of low clutch brings about a lower gear position that needs a larger torque contribution. The switching movement of the switching valve is effected by a high clutch pressure applied to the high clutch.

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Shizuoka, Japan

Takashi Sano